Liquid Trade Waste - Hawkesbury City Council

LIQUID TRADE WASTE
Discharge Categories and Management
Guidelines
To be read with Hawkesbury City Council’s Liquid
Trade Waste Policy, adopted November 2011
January 2016
Table of Contents
Section 1
Introduction .......................................................................................................................... 1
Section 2
Discharge categories and procedure for approval .............................................................. 2
Trade Waste Discharge Categories .................................................................................................... 3
Category 1a (Commercial) .............................................................................................................. 3
Category 1b (Industrial) ................................................................................................................... 3
Category 2 ....................................................................................................................................... 3
Category 3 ....................................................................................................................................... 4
Category 4 ....................................................................................................................................... 4
Category 5 (Special wastes) ........................................................................................................... 4
Fees and Charges ............................................................................................................................... 5
Category One through Four ............................................................................................................ 5
Category Five .................................................................................................................................. 5
Procedure for Approval ........................................................................................................................ 6
General ............................................................................................................................................ 6
Procedure ........................................................................................................................................ 6
Considerations ................................................................................................................................. 6
Plan of Management ....................................................................................................................... 7
Approvals: (Registration, Letter of Permission, Formal Agreement) ................................................... 7
General ............................................................................................................................................ 7
Registration ..................................................................................................................................... 7
Letter of Permission......................................................................................................................... 7
Formal Trade Waste Agreement ..................................................................................................... 8
Sampling and Analysis ........................................................................................................................ 8
General ............................................................................................................................................ 8
Compliance and New Installations .................................................................................................. 8
Full Scale Monitoring and Reporting ............................................................................................... 8
Pollution Profile................................................................................................................................ 8
Flow Measurement .......................................................................................................................... 8
Section 3
Guidelines for managing Trade Waste................................................................................ 9
Introduction ........................................................................................................................................ 10
Why Manage Trade Waste? .............................................................................................................. 10
High BOD ...................................................................................................................................... 10
Suspended Solids.......................................................................................................................... 10
Grease and Oil .............................................................................................................................. 10
Low or High pH .............................................................................................................................. 10
High Temperature.......................................................................................................................... 11
Heavy Metals ................................................................................................................................. 11
Sulphur Compounds ...................................................................................................................... 11
Detergents ..................................................................................................................................... 11
Flammable Substances ................................................................................................................. 11
Cyanide ......................................................................................................................................... 11
Phenolic Substances ..................................................................................................................... 11
Chlorinated Solvents ..................................................................................................................... 11
Pesticides ...................................................................................................................................... 11
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Trade Waste Pre-Treatment Equipment (overview) .......................................................................... 12
General .......................................................................................................................................... 12
General Installation Requirements for Pre-Treatment Equipment .................................................... 13
General .......................................................................................................................................... 13
Electrical Equipment used in Treating Liquid Trade Waste .............................................................. 13
Methods of Containment ................................................................................................................... 13
Roofing of Liquid Trade Waste Generating Areas ........................................................................ 13
Bunding ......................................................................................................................................... 13
Speed Humps ................................................................................................................................ 14
Minimum Treatment Requirements for Trade Waste ........................................................................ 15
Trade Waste Pre-Treatment (Use Of Equipment) ............................................................................. 21
Screens ......................................................................................................................................... 21
Dry Basket Arrestor ....................................................................................................................... 21
Application ..................................................................................................................................... 21
Grease Arrestors ............................................................................................................................... 22
Conventional Grease Arrestors ..................................................................................................... 22
Modular Grease Trap (MGT) ......................................................................................................... 22
Grease Extractor ........................................................................................................................... 22
Sizing of a Grease Arrestor ........................................................................................................... 22
Maintenance of Arrestors, MGT’s and Extractors ......................................................................... 23
Under-sink Pump Units ................................................................................................................. 23
General .............................................................................................................................................. 23
Cleaning Compounds .................................................................................................................... 23
Pumps ........................................................................................................................................... 23
Coalescing Plate Interceptor (CPI) ................................................................................................ 24
Hydrocyclone Separation System (HSS) ...................................................................................... 24
Vertical Gravity Separator (VGS) .................................................................................................. 24
Maintaining Oil Separators ............................................................................................................ 24
Service Station Forecourts ................................................................................................................ 25
Stormwater Containment ................................................................................................................... 25
Roofing of Liquid Trade Waste Generating Areas ........................................................................ 25
Method of Exclusion of Stormwater............................................................................................... 25
Separation ..................................................................................................................................... 25
Bunding ......................................................................................................................................... 25
Collection Drains ........................................................................................................................... 26
Diversion Drains ............................................................................................................................ 26
Speed Humps ................................................................................................................................ 26
Housekeeping practices for kitchen and oily waste........................................................................... 26
Kitchen Type Waste ...................................................................................................................... 26
Workshops, Garages, Service Stations......................................................................................... 26
Glossary ................................................................................................................................................ 28
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Section 1 Introduction
Hawkesbury City situated within the catchment of the Hawkesbury-Nepean River system is one of
many communities that discharge treated sewage effluent into the river. Two sewerage authorities
operate within the City, Sydney Water and Council itself, each operating two wastewater treatment
plants. With increased pressure on public authorities and governments from public awareness
regarding environmental quality, more stringent regulations controlling the quality of treated effluent
discharged to receiving waters are being enforced through the Office of Environment and Heritage
(OEH).
Hawkesbury City Council is licensed by the OEH to discharge treated effluent to receiving waters with
strict limits on the pollutant levels of the effluent. Failure to comply with these license agreements can
incur heavy financial penalties; as these penalties would be paid for with public funds, it is essential
that Council maintain its wastewater treatment plants at optimum performance levels. With this in
mind, it becomes necessary to control the quality of the influent to the treatment plants. This is to be
achieved by implementing this Trade Waste Policy, to register all non-domestic liquid wastes capable
of being discharged to Council's sewerage system and to insure that all toxic liquid wastes are
disposed of properly through the appropriate authority.
This document is divided into three main parts being Hawkesbury City Council’s Liquid Trade Waste
Policy was adopted by Council in November 2011; Categories and Procedure for Approval to
Discharge and Guidelines: Managing Trade Waste.
In the Hawkesbury City Council’s Liquid Trade Waste Policy, trade waste is defined and the purpose
and objectives of the policy are presented. The ultimate aim, with regard to pre-treatment is that all
liquid trade waste discharged to the local sewerage system complies with the standards set out in
Schedules ‘A’ & ‘B’ included in the Policy Statement.
In this document, Section 2: Categories & Procedures for Approval to Discharge, provides details of
the discharge categories that are presented along with the procedure to receive permission to
discharge liquid trade waste to Hawkesbury City’s sewerage system.
In Section 3: Guidelines for Managing Trade Waste, advice and guidelines are provided with regard to
pre-treatment equipment, housekeeping sampling and flow monitoring and stormwater management.
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Liquid Trade Waste
Section 2 Discharge categories and procedure for approval
Discharge categories and
procedure for approval
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Trade Waste Discharge Categories
Category 1a (Commercial)
Domestic type wastes in low mass loadings (low volume and low strength), examples include but are
not limited to take away food bars, butchers, dry good sales, clean dry trades-no showers, etc.:
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volume not to exceed 1kL/day
BOD5 not to exceed 250mg/L
suspended solids not to exceed 200mg/L
oil and grease not to exceed 50mg/L
all other substances are not permitted to be discharged.
Trade waste charges are covered by Council’s business sewer rate for a Category 1 discharge.
Category 1b (Industrial)
Domestic with some non domestic type wastes in low mass loadings (low volume and low or high
strength), examples include but are not limited to dental surgeries, hairdressers photo processors,
some service stations, x-ray laboratory, panel beating/spray painting etc.:
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volume not to exceed 1kL/day
BOD5 not to exceed 250mg/L
suspended solids not to exceed 200mg/L
oil and grease not to exceed 50mg/L
all other substances must comply with Schedule A (see Part 1: Policy Statement)
the waste-stream must comply with Schedule B (see Part 1: Policy Statement).
Trade waste charges are covered by Council’s business sewer rate for a Category 1 discharge.
Category 2
Domestic type wastes in higher mass loadings (high volume low strength) with the inclusion of some
non domestic wastes, examples include but are not limited to small restaurants and laundries, small
shopping centres, dirty dry trades-showers, car detailing etc.
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volume not to exceed 5kL/day
BOD5 not to exceed 250mg/L
suspended solids not to exceed 200mg/L
oil and grease not to exceed 50mg/L
all other substances must comply with Schedule A
the waste-stream must comply with Schedule B.
Trade waste charges are covered by Council’s business sewer rate for a Category 2 discharge.
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Liquid Trade Waste
Category 3
Medium volume discharges and/or higher loads of industrial wastes examples include but are not
limited to hospitals, food and dry good manufacturing, metal processing, larger restaurants, laundries
or shopping complexes etc.
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volume not to exceed 10kL/day
volume may have to be monitored by a flow meter
pollutants may have to be monitored on a regular basis
the waste-stream must comply with Schedule A
the waste-stream must comply with Schedule B.
Trade waste charges for volume discharge are covered by Council’s business sewer rate for a
Category 3 discharge. Additional charges may be levied for mass loads.
Category 4
Larger volume discharges and/or higher loads of industrial wastes examples include but are not
limited to hospitals, food and dry good manufacturing, metal processing, larger restaurants, laundries
or shopping complexes etc.
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volume not to exceed 20kL/day
volume must be monitored by a flow meter
pollutants may have to be monitored on a regular basis
the waste-stream must comply with Schedule B.
Trade waste charges for volume discharge are covered by Council’s business sewer rate for a
Category 4 discharge. Additional charges may be levied for mass loads.
Category 5 (Special wastes)
Trade wastes which:
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exceed the limits set in Category 4.
Volume exceeds 20kL/day except where:
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4.
5.
volume does not exceed 5 % of the design capacity of the sewerage treatment plant
volume does not exceed 0.5 % of the design capacity if heavy metals or other toxic
substances are discharged
volume must be monitored by a flow meter
pollutants may have to be monitored on a regular basis.
The waste-stream must comply with Schedule B.
Are considered by Council to be of a sensitive nature (e.g. chemical wastes).
Ship to Shore: Any liquid waste that is pumped to the sewer via the collection facility at
Windsor wharf.
Mobile Businesses: Any liquid waste collected by a mobile service and returned to base for
discharge through a designated point.
Sullage: Liquid waste collected from septic pump outs by tanker and discharged at South
Windsor Treatment Plant.
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Liquid Trade Waste
Category 5 Trade Waste Charges for volume discharge are covered by Council’s Business
Sewer Rate for a Category 4 discharge plus an excess charge per kilolitre over the 20 kL/day
limit. Additional charges may be levied for mass loads.
Fees for Ship to Shore and Mobile Businesses are based on the capacity of the holding tank
and/or frequency of discharge.
Fees for sullage are based on a fixed residential rate for domestic sullage or a rate per kilolitre
for sullage removed from a business.
Fees and Charges
Trade Waste fees and charges are set out in Hawkesbury City Council's Revenue Pricing Policy. This
document is available to the public and is reviewed annually.
Category One through Four
Volume: A standard business sewer rate per annum applies based on average daily discharge.
Mass Load: Fees for Mass Load may apply to these categories depending on the pollutant
concentrations.
Category Five
Volume: The standards business sewer rate applies for Category Four plus an excess per kilolitre.
Mass Load: An additional fee may apply for mass pollutant loads.
Ship to Shore: Standard business sewer rates apply depending on the size of the holding tank
and/or frequency of discharge.
Mobile Business: Standard business sewer rates apply depending on the size of the holding tank
and/or frequency of discharge.
Sullage: Standard residential rates apply for domestic sullage or a rate per kilolitre if collected from a
business, home business or cottage industry.
Charge Rates: Charge rates have been established for excess volume discharge, mass load and
mass load attributed to pollutant concentrations above standard limits.
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Excess volume: price/kilolitre
Biochemical Oxygen Demand, Suspended Solids, total Grease & Oil: price/kilogram
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Liquid Trade Waste
Group 1 to 4 Pollutants: Pollutants listed in Schedule 'A' has been divided into four groups based on
their detrimental effects on the treatment process; Group 1 being the least expensive to treat and
group 4 the most expensive (price/kilogram)
Application Fee: The application fee will cover the assessment, one inspection and initial permission
for Categories 1, 2 & 3 discharges.
Agreement Fee: Fee for preparation of formal Service Agreement.
Procedure for Approval
General
Under Section 68 of the Local Government Act, 1993 a person is required to obtain approval from a
Council prior to discharging waste into the sewer of a council.
Procedure
1.
Obtain a Trade Waste application from Council’s Customer Service Counter staff and fill in as
much information as possible. If you as the applicant are a tenant of the subject property from
where the trade waste discharge will originate, please include the owner’s or the property
manager’s contact details on the application. This information can be added to the last page
under 'Other Details'. If this application is being lodged as a condition of consent in a
Development Application please include the DA number on the application: again use the
space marked 'Other Details'.
2.
The applicant must submit a draft ‘Plan of Management’ along with the application if the
application is for a Category 4 or 5 discharge. This plan will be reviewed during assessment
and revised accordingly when approval is granted.
3.
Pay the appropriate fee to the cashier (Trade Waste application fee is listed under ‘Fees and
Charges’ in Council’s Revenue Pricing Policy) and return the completed application to Council’s
Trade Waste Officer or return it to staff at the Customer Service Counter with instructions to
hand to the Trade Waste Officer.
4.
The applicant will be notified as soon as the application has been assessed.
Considerations
Council’s decision to accept any commercial or industrial discharge to the sewer system will be based
on meeting council’s requirements. When determining a trade waste application, Council officers will
consider the following factors:
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the potential for the waste to impact on public health
the possible impacts the discharge may pose to the environment (land, water, air, noise
or nuisance factors)
the potential impacts of the waste on the health and safety of Council’s employees
the possible impact of the waste on Council’s sewerage infrastructure and the sewage
treatment process
the capability of the sewerage system (both transportation and treatment components) to
accept both the quality and the quantity of the proposed waste
the impact the waste will have on the ability of the Sewage Treatment Plant to meet the
OEH license requirements
the potential impacts of the waste on the quality of, and management practices for,
effluent and biosolids produced from the sewage treatment process.
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the adequacy of the pre-treatment process to treat the waste to a level acceptable for
discharge to the sewerage system, including proposed safeguards if the pre-treatment
system fails (if applicable)
whether appropriate safeguards are proposed to avoid the disposal of other nonapproved wastes to the sewerage system
the adequacy of any chemical storage and handling facilities, and the proposed
safeguards for preventing the discharge of chemicals to the sewerage system
whether the disposal of prohibited substances is proposed
the potential for stormwater entering the sewerage system and adequacy of the
proposed stormwater control
the adequacy of the proposed due diligence program, contingency plan and plan of
management with regard to trade waste where required.
Plan of Management
All trade waste activity must incorporate a Plan of Management. This can be as simple as marking in
a diary or on a calendar the date a grease trap is due for a pump-out and clean.
The more complex the process, the more involved the management plan. This could include daily,
weekly, monthly or quarterly items regarding cleaning procedures, scheduled maintenance, housekeeping, monitoring the waste-stream, sampling and analysis and a contingency plan with regard to
spills.
Approvals: (Registration, Letter of Permission, Formal Agreement)
General
All trade waste activity must be registered by Council regardless of the nature of the activity. The most
basic activity that which is less than 1000 l/day and need no pre-treatment may not need any special
permission or agreement, just registered on the Trade Waste Database. However, small businesses
with minimum pre- treatment facilities will require a Letter of Permission. Businesses with a large
volume and/or mass load discharge and more complicated pre-treatment facilities will require a formal
Trade Waste Agreement.
Registration
Any Category 1business activity that does not require any pre-treatment to their waste-stream or pose
a potential risk of a banned substance entering the sewer system will only require registration on
Council’s Trade Waste Database.
Letter of Permission
Category 1 businesses with pre-treatment and Category 2 businesses will require a Letter of
Permission. These are businesses where the volume discharge upper limit is 1000 L/day and 5000
L/day respectively, where their mass load is limited as per Schedule ‘A’ and there are minimum pretreatment requirements.
A Category 3 business is one with a discharge between 5000 and 10,000 L/day and depending on the
nature of the waste-stream and mass load will determine whether it will need a ‘Letter of Permission
or a formal Trade Waste Agreement to discharge to the sewerage system.
The Letter of Permission is subject to an annual renewal.
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Formal Trade Waste Agreement
Category 4 and 5 businesses will require a formal Agreement. These are businesses with discharges
up to and greater than 20,000 L/day. Their waste-stream has significant mass loads and their pretreatment process is more complex. A formal Agreement is a scheduled document that details the
nature of the waste-stream, sampling and analysis, any fees and charges and how they are
calculated, pre-treatment infrastructure and any special conditions necessary to comply with Schedule
‘A’ & ‘B’ of the policy. A formal Agreement must be renewed every three years. If circumstances
warrant, a formal Agreement may be renegotiated during the term of the agreement.
Sampling and Analysis
General
All businesses that require some form of pre-treatment will get involved in sampling and analysis (S
and A). All pre-treatment devices when installed must be fitted with a sampling point. S and A can be
quite simple from compliance checks and checking to see if newly installed pre-treatment equipment
is operating properly, to full-scale daily monitoring and reporting. The cost of all sampling and analysis
is the responsibility of the trade waste customer.
Compliance and New Installations
S & A for compliance is done at the discretion of Council Officers. It may be a random sample, taken
due to a complaint or taken at time of an inspection.
All newly installed pre-treatment equipment will be inspected and samples taken for analysis within 30
days of commencement of operation. This is to ensure that the installation is correct and the wastestream meets the standards as set out in schedule ‘A’.
Full Scale Monitoring and Reporting
When deemed necessary that a business must monitor its trade waste activity daily, weekly, or
monthly; it becomes necessary to set a system in place to make this possible. Composite samples
are best collected by an ‘autosampler’ on either a time or flow basis. This way samples can be
collected every hour or every 10 kilolitres as an example. At the end of the day all the samples can be
combined and a composite sample can be drawn from the total volume and preserved for analysis.
This type of sampling averages minor changes in pollutant concentrations in the waste-stream
throughout the day. If the pollutant concentration in the waste-stream is consistent throughout the day
then a grab sample may be all that is required.
Pollution Profile
When a waste-stream is unpredictable or a complete unknown, a pollution profile must be compiled to
establish the quality of the waste-stream. 20 composite samples must be collected, one sample per
day over 20 consecutive production days and sent for analysis. This will establish the quality of the
waste-stream and a starting point for management of the wastestream.
Flow Measurement
Where daily volume discharge exceeds 5 kilolitres per day, it must be measured using an appropriate
flow meter. Where the discharge is less than 5 kilolitres per day a discharge factor can be applied to
the water account.
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Liquid Trade Waste
Section 3 Guidelines for managing Trade Waste
Guidelines for managing
Trade Waste
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Introduction
Sewerage systems are generally designed to safely transport and treat domestic sewage. Provided
that there is available capacity in the sewerage system, the Council may accept the waste generated
by commercial and industrial activities into the sewerage system as a service to business and
industry.
Why Manage Trade Waste?
Uncontrolled discharge of liquid trade waste into the sewerage system can cause serious problems to
the sewerage infrastructure, environment and health and safety of workers and public. These
potential problems are listed below.
High BOD
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May accelerate the generation of sulphides in sewer mains and consequently odours and
corrosion problems.
May overload treatment units at the sewage treatment plant (STP).
May cause non-compliance with the STP license conditions.
Suspended Solids
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Can cause blockages in the drains of commercial and industrial properties and sewage
overflows to the environment.
Can form deposits in the sewers reducing its capacity and can lead to overflow condition.
Accumulate in wet wells and pump stations resulting in increased maintenance.
Can deteriorate mechanical equipment (pumps and valves) by abrasion.
Overload treatment units at the STP.
Grease and Oil
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Cause overflows to the environment from the drains of commercial and industrial properties.
Cause formation of deposits of greasy solids in the sewage transportation system thereby
reducing its carrying capacity. These deposits can lead to the breakaway of accumulated
grease at times of high or very low flow.
Accumulates in wet wells and pump stations causing blockages, failure of pumps and leads to
an increase in maintenance.
Deposit in bends of the sewer and cause restrictions and blockages.
Accumulate on screens at treatment facilities causing blockages.
Reduce the efficiency of sewage treatment processes.
Can cause non-compliance of the stp's effluent with license conditions.
Form an oily film on the receiving water.
Low or High pH
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Can injure people working in and around the sewerage system.
Can corrode sewerage infrastructure.
Can upset biological treatment process at the stp.
Can cause the release of toxic gas, hydrogen sulphide in the case of low ph and ammonia in
the case of high ph.
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Liquid Trade Waste
High Temperature
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Encourages volatile materials to be driven from the sewage into the atmosphere.
Increase rates of reaction within sewer mains resulting in consumption of oxygen and high
levels of noxious gases increasing odours.
Can cause damage to sewers including loss of strength of plastic components.
Heavy Metals
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May inhibit sewage treatment processes.
Accumulate in biosolids and therefore limit its beneficial reuse.
Metal residual discharged with sewage effluent may pollute the environment, accumulate in
aquatic organisms and move up the food chain.
Sulphur Compounds
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Sulphites consume oxygen and may cause anaerobic conditions.
Sulphates can reduce to sulphides.
Sulphides can cause odours and corrosion problems in sewers.
Sulphides may result in the release of toxic hydrogen sulphide gas.
Detergents
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Toxic to living organisms.
May cause foaming problems in sewers and the STP.
Flammable Substances
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Can cause fires and explosions in the sewerage system.
Cyanide
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Toxic to living organism.
May produce toxic gas in the sewer.
Phenolic Substances
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May inhibit sewage treatment processes.
Chlorinated Solvents
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May inhibit sewage treatment process.
Are toxic to people working in and around the sewerage system.
Pesticides
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Can inhibit sewage treatment processes.
Can pass unchanged through the STP and adversely affect the environment.
Limit the beneficial reuse of the STP effluent and biosolids.
Organochlorine pesticides are persistent in the environment and accumulate in living
organisms.
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Liquid Trade Waste
Trade Waste Pre-Treatment Equipment (overview)
General
There are many types of 'off the shelf' pre-treatment devices on the market to suit many varied trade
waste discharges. Listed below are the more common devices on the market. Consult with Council's
Trade Waste Officer as to which device will best suit your needs.
Amalgam Separator: this device removes the amalgam produced as a result of dental procedures.
Coalescing Plate Interceptor/Separator (CPI or CPS): the separator uses a gravity process to
remove non-emulsified oil and solids from wastewater. It contains a pack of plates that enhances the
gravity separation process. 'Quick Break' detergents and non-emulsifying pumps must be used with
this equipment.
Cooling Pit/Tank: a pit or tank used to cool wastewater to 38ºC or less, prior to discharge to sewer.
Dilution Pit/Tank: a pit or tank used to balance high strength discharge 'peaks'. Mixing of acidic and
alkaline wastes to bring the pH into an acceptable range to discharge to the sewer.
Dry Basket Arrestor: a pit or tank fitted with a fixed screen and removable mesh basket to capture
large solids and fibrous material (e.g. lint, fish scales). There are also in-floor dry basket arrestors
available with a fixed screen fitted to a floor waste and a removable basket as well as in-sink dry
arrestors.
General Purpose/Solid Settlement Pits: a general purpose pit or tank that allows solids to sink and
grease or oil to float, thereby removing them from the wastewater.
Grease Arrestor: an above ground tank or in-ground pit that allows kitchen wastewater to cool and
grease to separate from the wastewater.
Grease Extractor: a grease extractor is a tank with an effluent filter on the outlet pipe work of the
tank.
Hydrocyclone Separation System: this system uses centrifugal force to separate grease/oils from
wastewater.
Modular Grease Trap (MGT): this is a modular system of connecting units of plate packs together to
adjust the capacity of the grease trap as required. A surge control device must be fitted to the last
module.
Plaster Arrestor: an under sink arrestor to capture and settle plaster used in medical procedures or
craft workshops.
Silver Recovery Unit: this unit recovers silver from photographic solutions by either electrolytic or
chemical processes.
Vertical Gravity Separator (VGS): a separator that uses a vertical cylinder design containing a
continuous truncated conical spiral pack to separate non-emulsified oils and solids from wastewater.
Under Sink Pump Unit: a small volume tank with a pump that transfers collected kitchen wastewater
to a grease trap.
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Liquid Trade Waste
General Installation Requirements for Pre-Treatment Equipment
General
The liquid trade waste pre-treatment equipment must be installed in accordance with the relevant
regulations: NSW Code of Practice: Plumbing and Drainage, AS3500-National Plumbing and
Drainage Code, local Council requirements if any and the manufacturer's guidelines. The pipes and
connecting fittings must also comply with these codes and standards. The plumbing and drainage
work must be carried out by a licensed plumber.
Electrical Equipment used in Treating Liquid Trade Waste
Flammable Class 3 liquids (see Occupational health and Safety Amendment 'Dangerous Goods'
Regulation 2005), such as petrol, kerosene or solvents are potentially dangerous in the workplace.
Although these substances must not be discharged to the sewerage system, there is the potential for
them to be present or situated near trade waste treatment facilities.
Where a treatment process has flammable liquids present, all electrical equipment within a defined
area must be intrinsically safe to avoid a dangerous situation occurring. A discharger must check that
the electrically operated pump and other electrical devices have the correct electrical rating for a
particular installation. All work must be carried out by a licensed electrical contractor.
Methods of Containment
Roofing of Liquid Trade Waste Generating Areas
When a liquid trade waste generating or pre-treatment process does not fully occur within a building,
suitable roofing must be provided to prevent the ingress of stormwater to the sewerage system.
Bunding
A bund is defined by AS4452B 1997 "as an impervious embankment of earth, or a wall of brick,
concrete or other suitable material, which may form part or all of the perimeter of a compound that
provides a barrier to retain liquid".
All liquid trade waste pre-treatment systems and any substance which could adversely affect the
sewerage system, the environment or safety of people must be contained in bunded areas, so that
any leaks, spillages and/or overflows cannot be directly discharged into the sewerage and/or storm
water systems. Leaks, spillages and overflows from a bunded pre-treatment area must be pumped
back to the head of the pre-treatment system.
The net capacity of a bund should be sufficient to contain 110% of the largest container; this is to
provide an allowance for stormwater. Allowances should also be made for the capacity displaced by
other tanks, barrels or drums stored within the bunded area. For the storage of any flammable liquids,
NSW Fire Brigades recommends that the capacity be increased to 133% of the capacity of the largest
tank to allow for the capture of fire water.
A collection sump must be provided in the bund floor for the isolation and removal of liquids. All
pipework should go over the wall rather than through the wall. There should be no drain valves in the
pipework from the bunded area, as they can be accidentally or intentionally left open to drain.
For other requirements in regard to bunding refer to the OEH document Bunding and Spill
Management available on the OEH internet site.
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Liquid Trade Waste
Speed Humps
These are similar to the devices used on roadways where it is desirable to reduce speed. In this case,
it is used to contain spills and to separate potentially contaminated areas from clean areas without
impeding traffic flow. If bunding is to be driven over, it has to comply with AS2890:1 for speed humps.
Speed humps can be used around such areas as fuelling facilities or truck unloading areas,
particularly at storage tanks and remote fill points. A pit is incorporated into the system to isolate
contaminated flows for pumping out and disposal through an appropriate onsite pre-treatment facility
or removed from site and discharged at an appropriate waste disposal facility.
Speed humps can also be used as a form of containment where relatively small spills are likely to
occur.
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Liquid Trade Waste
Minimum Treatment Requirements for Trade Waste
Activity
Characteristics of Waste
Minimum Pre-treatment Required
Automotive/Engineering
Auto dismantler
Bus/coach depot wash bay area
Oil, Grease, Suspended solids,
Petroleum hydrocarbons, Metals,
Solvents, Detergents
Dry basket arrestor.
Collection pit sized to suit, minimum capacity
300L.
Car detailing
An oil/water separator, sized accordingly
(Note1).
Mechanical workshop
Reuse of wash water.
Service stations
(workshop only)
Carwash - manual
Carwash - automated
Carwash with engine
degreasing
Equipment hire
Oil, Grease Suspended solids,
Detergents, Solvents
Dry basket arrestor.
Collection pit sized to suit, minimum capacity
300L. an oil/water separator, sized
accordingly (Note1).
Construction equipment
maintenance
Truck wash (external only)
Panel beater/spray painter
Oil, Grease, Suspended solids
Dry basket arrestor.
Collection pit sized to suit, minimum capacity
300L.
An oil/water separator, sized accordingly
(Note1).
Discharge from spray booth area not
permitted.
Paint solvents, thinners are not permitted
into the sewer.
Radiator repair
Suspended solids, pH, Metals
Solids settlement pit.
Metal removal and pH adjustment may be
required before discharge to sewer.
Capture radiator fluid for reuse or store and
remove by licensed contractor.
Floors must be bunded to prevent spillage
draining to the sewer.
Food Service Industry
Food Service Industry
Food Service Industry
Hawkesbury City Council
15
Liquid Trade Waste
Activity
Characteristics of Waste
Minimum Pre-treatment Required
Food Service Industry
Barbequing process
BOD, Suspended solids, Grease
Grease arrestor, for steam oven or gas vat
minimum capacity 2000L, otherwise 1000L
minimum capacity (Note 2).
The fat and oil generated by barbequing
processes and discreet oil must be collected
for recycling and must not drain directly to a
grease trap or sewer. Only the wash water
can drain to the sewer via a grease trap.
Collected fat for recycling must be removed
by a licensed contractor.
Bakery - hot bread only no meat
or dairy products cooked on
site.
BOD, Suspended solids
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
BOD, Suspended Solids, Grease
Grease arrestor, sized accordingly, minimum
capacity 1000L.
Kitchen waste - no hot food
prepared and/or no oily greasy
waste generated.
Fruit & Vegetable market (retail)
Supermarket with fruit/vegetable
section.
Butcher retail
Supermarket with butcher
and/or seafood section
Butcher wholesale
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
BOD, Suspended solids, Grease
Grease arrestor, sized accordingly, minimum
capacity 1000L.
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
Commercial Kitchen/Caterer
BOD, Suspended solids, Grease
Bakery-cooking meat and dairy
products on-site
Grease arrestor, sized accordingly, minimum
capacity 1000L.
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
Chicken (fresh) retail only
Kitchen waste-hot food
prepared and/or oily greasy
waste is generated
Food Service Industry
Food Service Industry
Food Service Industry
Food Service Industry
Food Service Industry
Hawkesbury City Council
16
Liquid Trade Waste
Activity
Characteristics of Waste
Minimum Pre-treatment Required
Food Service Industry (continued)
Fast food outlets (e.g. KFC,
McDonalds, Red Rooster, Pizza
Hut)
BOD, Suspended solids, Grease
Grease arrestor, sized accordingly, minimum
capacity 1500L.
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
Fish-fresh (retail) no cooking on
site and not including large sites
such as Fish Co-op
BOD, Suspended solids, Grease
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
Fish Shop cooking on-site
BOD, Suspended solids, Grease
Grease arrestor, sized accordingly, minimum
capacity 1000L.
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
Kitchen waste-wok burner
BOD, Suspended solids, Grease,
large volumes of hot water
Grease arrestor, sized accordingly, minimum
capacity 1500L.
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
Cooling pit and water saving practices need
to be implemented.
Oyster processing
Grit, Suspended Solids
Dry basket arrestor, solids settlement pit,
minimum capacity 1000L.
Restaurants, Takeaways, Cafés
BOD, Suspended solids, Grease
Grease arrestor, sized accordingly, minimum
capacity 500L.
Sink screens and in floor dry basket
arrestors in food preparation and handling
area.
Medical Services
Dental Surgery
Amalgam
Amalgam separator built into the cuspidor.
•
•
•
Suspended Solids
Plaster Arrestor.
Silver, Ammonia, Thiosulphate,
Sulphite
See Photographic Waste.
Suspended Solids
Plaster Arrestor
Doctor Surgery, Medical Centre
Suspended Solids
Plaster Arrestor
•
•
Silver, Ammonia, Thiosulphate,
Sulphite
See Photographic Waste
dental chair
plaster casts
x-ray
Dental Technician
•
Plaster casts
Plaster casts
x-ray
Food Service Industry
Food Service Industry
Hawkesbury City Council
17
Liquid Trade Waste
Activity
Characteristics of Waste
Minimum Pre-treatment Required
Medical Services (continued)
Hospital/Nursing Home
•
•
BOD, Suspended solids, Grease,
High Temp.
Solid waste
Food waste disposal
units
Contaminated/infectious
waste
•
Discharge of solid waste and waste from
devices that macerate or pulverise solid
waste are prohibited.
The installation of food waste disposal units
is not permitted.
Existing installations in hospitals may be
allowed provided the waste water is
discharges through an adequately sizes
grease trap.
For other sources of waste, e.g.
kitchen, x-ray, various
laboratories, laundry, plaster
casts refer to relevant clauses in
this table.
Contaminated and/or infectious waste must
be sterilised by autoclave and removed from
site by a licensed contractor.
Other Services
Carpet cleaning mobile unit
BOD, Suspended Solids, Grease,
20 micron or smaller filtration system fitted to
the mobile unit.
Crafts - ceramic, pottery, gem
stones, jewellery (e.g. hobby
clubs, schools cottage
industries.
Suspended Solids
No pre-treatment.
Plaster arrestor.
Settling pit sized accordingly minimum
capacity 1000L.
Flow:
•
•
•
<200L/day
200L to 1oool/day
>1000L/day
Dry Cleaning
Solvents
Dry cleaning solvents are not permitted into
the sewer.
Florist
Suspended Solids
Sink screens and in-floor dry basket arrestor.
Funeral Parlour
Suspended Solids
In-floor dry basket arrestor.
Screen at table drainage point.
Suspended Solids, Grease
Fixed screen over floor waste.
•
•
Morgue
Autopsy table
Garbage bin cleaning
•
Liquid waste discharged via grease trap.
hotels, restaurants,
shopping centres
Glass cutting (non optical
services)
Suspended Solids
Solids settlement pit, minimum 2 hours
detention at maximum flow rate. Cleaning of
pit before settled material exceeds 200mm in
thickness.
Hair dressing Salon
Sink screens and dry basket arrestor for
floor waste.
Food Service Industry
Food Service Industry
Food Service Industry
Hawkesbury City Council
18
Liquid Trade Waste
Activity
Characteristics of Waste
Minimum Pre-treatment Required
Other Services (continued)
Kennels, Dog grooming, Pet
Shop
Suspended Solids
Sink screens and in floor dry basket
arrestors.
Animal faeces should be collected and not
discharged to the sewer.
Laboratory School
Chemicals
1000L dilution pit/tank
Other Services (continued)
Commercial laboratory chemical
related
Chemicals
Dilution pit/tank sized according to a flow
rate, minimum capacity 1000L, pH correction
may be required.
Laboratory, pathology including
autopsy, hospital
Chemicals
Dilution pit/tank sized according to a flow
rate, minimum capacity 1000L, pH correction
may be required.
Solid and. /or liquid waste
Contaminated/infectious waste
Contaminated and/or infectious waste must
be sterilised by autoclave and removed from
site by a licensed contractor.
Laundry (coin operated)
Lint, High temperature
Lint screens 1mm mesh (washing machine
internal screens acceptable).
Cooling pit capacity calculated to reduce
wastewater temperature to <38ºC
Laundry (commercial or
industrial)
Suspended Solids, Lint, High
temperature
Solids settlement and cooling pit, Lint
screens, pH adjustment.
Optical services (grinding of
glass and plastic)
Suspended Solids
Baffled settlement tank, minimum 1 hour
detention and easy access for cleaning.
Shopping Centre (including food
preparation)
Refer to relevant types of business in this
table.
For sizing a grease trap, see Note 2
Swimming Pool (municipal)
Suspended Solids, Chlorine
Hydrotherapy pool
Backwash from a sand filter is accepted into
the sewer from a holding tank. T he waste is
to be discharged at a controlled flow rate.
The discharge is to be limited to low flow
periods.
Diatomaceous earth backwash must be
discharged to the sewer via a settling pit with
a min. 1hour detention time.
Swimming Pool (domestic)
•
•
Suspended Solids
Backwash from a sand filter may be
discharged to the sewer.
Sand filter
Diatomaceous earth filter
Backwash from a diatomaceous earth filter
must not be directly discharged to the sewer.
School
•
•
Refer to Food Service Industry section.
Balance/dilution tank to be sized for 1 hour
retention.
Canteen, home science
Photographic/science
laboratory
Food Service Industry
Hawkesbury City Council
19
Liquid Trade Waste
Activity
Characteristics of Waste
Minimum Pre-treatment Required
Other Services (continued)
Veterinary Premises
Suspended Solids
•
Silver, Ammonia, Thiosulphate,
Sulphite
x-ray
Sink screens and in-floor dry basket
arrestors.
Animal faeces should be collected and not
discharged to the sewer.
See photographic waste
Photographic Waste
Photographic processing and
developing including x-ray
Silver, Ammonia, Thiosulphate,
Sulphite
Balance and or dilution tank, silver recovery
unit for silver bearing waste (Note 3) or
remove all silver bearing waste from
premises by licensed contractor.
Screen Printing
Suspended Solids, Petroleum
Hydrocarbons, Solvents Grease,
BOD, Silver, Ammonia, Thiosulphate,
Sulphite, Volatile Halocarbons.
Washdown bays, settling pits Coalescing
plate separator.
Stencil development, cleaning and
reclamation. Solvents used must be
reclaimed, stored and removed from site by
a licensed contractor. Silver bearing waste
must be treated in an SRU or removed from
site by a licensed contractor.
Miscellaneous (continued)
Boiler blowdown
Total Dissolved Solids, high
temperature
Cooling pit/tank to reduce wastewater temp
to <38ºC
Comfort cooling tower bleed off.
Corrosion inhibitors, biocides
No treatment.
The use of products containing
chromate is prohibited.
NOTES
1.
An oil interceptor/separator should be of an approved type such as a coalescing plate, vertical
plate gravity or a hydrocyclone separation system sized according to the influent flow rate. The
minimum size is 1000L/hr. Only ‘quick break’ detergents must be used with these systems. Wash
areas must be roofed, bunded and graded to exclude stormwater. In some instances where roofing
is impracticable a ‘first-flush’ system must be used.
2.
A grease arrestor should be an approved type and sized according to the influent flow rate. The
minimum size is 1000L.
3.
It is recommended that advice from a trade waste consultant should be sought in regard to
activities either not listed in the above table and/or involving a discharge greater than 20 kL/day.
Hawkesbury City Council
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Liquid Trade Waste
Trade Waste Pre-Treatment (Use Of Equipment)
Screens
The first step in pre-treatment is usually screening. Screens are an essential part and basic pretreatment requirement to prevent blockages and equipment failures. They will also help reduce the
cost of subsequent treatment stages.
A screen is used to retain or remove suspended or floating objects in wastewater. A screen may
consist of bars, rods, wires, gratings, wire mesh or perforated plates. Screen with openings of 3mm or
greater are considered coarse screens and those with openings less than 3mm are known as fine
screens.
The wide variety of screens reflects the range of application and the different mechanisms required to
keep them free of solids. They can include internal lint screen for washing machines and flat screens
that are cleaned by brushing or hosing to rotary or bar screens that are mechanically or manually
cleaned.
Dry Basket Arrestor
This is a pit or tank fitted with a fixed screen and a removable mesh basket. The fixed screen ensures
that if the operator neglects to re-install the basket, a failsafe mechanism is in place to continue to
capture gross solids.
There are also baskets available with a ‘shut-off’ valve that automatically stops discharge from the
waste outlet as soon as the basket is removed.
Application
Food Preparation Areas: A removable dry basket arrestor with a fixed screen must be fitted to all
floor wastes in food preparation and handling areas. There must also be a fixed screen over all floor
waste gullies.
Oily waste Areas: A dry basket arrestor or screen must be fitted to all floor wastes that drain to the
sewers to strain out gross solids such as rags, packaging, nuts and bolts etc.
In-sink Dry Basket Arrestor: This is a dry basket arrestor fitted in a sink with a fixed screen and a
removable mesh basket. There are arrestors with a mechanism that does not allow flow to the sewer
when the basket is removed.
Existing Arrestors without Dry Basket Arrestors: For existing premises without basket arrestors,
there are units available on the market that can be retro fitted into the existing pipe work.
Rotary Screens: These include externally and internally fed screens. Wastewater is fed over the
screen or out through the screen and the solids are collected based on the system used.
Rotary Inclined Drum Screen: As the screen rotates, the solids roll in the face of the drum and are
intercepted by diverter flights mounted spirally on the drum. Solids are directed up the inclined drum
to a discharge point and drop off into a bin or onto a conveyor or into a dewatering device.
Hawkesbury City Council
21
Liquid Trade Waste
Grease Arrestors
Conventional Grease Arrestors
There are two main types of conventional grease arrestors on the market the 'boat shape' and the
Sydney Water design which is a modified version of the boat shape. Both designs are acceptable for
most installations. The Sydney Water design is the preferred of the two as it has the following
advantages:
•
ease of service as the covers have been modified to provide better access for removal of
solids and grease and oil
•
the outlet has been raised so the solids are captured and removed rather discharged
than to the sewer.
Grease arrestors must be sized in accordance with the influent flow rate with a minimum size of 1000
litres.
Modular Grease Trap (MGT)
This is a system of connecting chamber units designed to separate oil, grease and settleable solids.
When sludge and oil/grease separate and build up in the first chamber the particles overflow into the
next. A surge control device (SCD) is fitted into the last chamber to stabilise high surges and promote
even flow and quality of the effluent. The SCD plates trap and deflect suspended particles back into
the chamber. The trap can be modified to increase retention time by adding chambers. Connecting
configurations should be no less than 1000L and no more than 5000L. An MGT can be very versatile
as they are more easily fitted into confined spaces and they do not have to be buried. They can even
be set up to fit in a basement of a premises and the effluent pumped into the sewer.
Grease Extractor
A grease extractor is a tank with either an effluent filter or anSCD on the outlet pipe. It can be used for
small operations and at premises where conventional grease arrestors cannot be installed due to
space limitations. The filter allows high hydraulic flows while grease and suspended solids
accumulate on the filter plate
A grease extractor with a SCD unit is designed to stabilise high hydraulic surges. The unit comprises
packed plates which will trap grease and suspended solids and deflect them back into the pretreatment vessel.
Where an existing grease arrestor is in good condition but failing to reduce grease and oils to less
than the standard concentration (50 mg/L), a grease extractor can be fitted to the outlet pipe, either
internally or externally housed in a separate pit.
Sizing of a Grease Arrestor
The minimum capacity for a conventional grease arrestor is 1000L. This assumes that a hot water tap
turned fully on will deliver 0.3 L/s or 1000 L/hr. Therefore, a volume of 1000L should enable one hour
detention time within the grease arrestor for cooling, which is considered a sufficient period for
breaking the emulsified grease and oil from the hot water solution.
Fast food outlets such as McDonalds, Red Rooster, KFC etc., require grease arrestors sized
according to the influent flow rate with a minimum capacity of 1500L. Barbequing process (steam
oven or gas vent) requires a grease arrestor minimum capacity of 2000L.
There are also some processes that generate high volumes of wastewater. These will be required to
install a grease trap sized in accordance with the influent flow rate.
Hawkesbury City Council
22
Liquid Trade Waste
Maintenance of Arrestors, MGT’s and Extractors
Remember, when locating these devices, they must be maintained, therefore allow reasonable
access to the site for equipment and the pump-out vehicle.
Servicing these devices is basically the same procedure as an initial pump-out, hose down (preferably
high pressure) walls and internal components and pump-out again. Refer to the manufacturer’s
specification for any specific procedure. Servicing intervals is a minimum four times a year (every 13
weeks). More frequent servicing may be required depending on the load on the device.
Under-sink Pump Units
There are some situations where it becomes necessary to install an under-sink pump unit, such as
space requirements or building design that does not allow a grease trap to drain to the sewer by
gravity. An under-sink pump unit consists of a tank that should not contain more than 40 litres of
kitchen wastewater. A pump located within the tank delivers this wastewater to a grease trap. The unit
should be cleaned at the same time the grease trap is serviced.
Oil Separators
Oily wastes (liquid wastewater containing residues of petroleum products) must be treated in an oil
separation system before discharge to the sewer. The oil separation system includes coalescing plate
interceptors/separators, vertical gravity separators and hydrocyclone separation systems.
General
Cleaning Compounds
Only ‘quick-break’ detergents should be used. ‘Quick-break’ detergents allow oil/water emulsion to
‘break’ or separate so that the oil separator removes the oil.
Since the advent of ‘quick-break detergents many chemical companies have labelled their products
as ‘quick-break’ when in fact they are not. The criterion is that the emulsion should break completely
and wastewater should separate into an oily and aqueous layer within 20 to 30 minutes.
The user should ensure that the supplied detergent is a ‘quick-break’ type. It should be verified on a
site specific basis that, while using a particular detergent, the emulsion breaks and the final liquid
trade waste discharge complies with the standard limits for oil and grease.
The use of degreasers is prohibited as they inhibit the detergent from breaking the emulsion and
therefore allowing petroleum hydrocarbons to enter the sewer system.
Pumps
A pump transferring wastewater from a collection pit to an oil separator should be a non-emulsifying
type with a suction inlet at least 300 mm above the bottom of the collection pit. It is important to use a
pump that is authorised by the manufacturer of the oil separator.
Hawkesbury City Council
23
Liquid Trade Waste
Coalescing Plate Interceptor (CPI)
A coalescing plate separator uses the difference in specific gravity to separate free (non-emulsified)
oil and solids from water. The pack of plates is placed across the direction of flow to assist this
process. Flow through is laminar to achieve optimum separation of oil from the water phase. The
plates are inclined 45 to 60 degrees from the horizontal so that solid particles caught by the plates
sink into the sludge hopper. The oil collects on the surface where it is decanted into the waste oil tank.
The plate packs are modular and can easily be removed for cleaning.
Some manufacturers supply plate packs for upgrading of existing pre-treatment facilities.
Coalescing plate interceptors should be sized in accordance with the influent flow rate. The minimum
size is 1000 l/hr.
Hydrocyclone Separation System (HSS)
This system is based on centrifugal forces separating immiscible, insoluble liquid-liquid mixtures. Oily
water is drawn off the top of a pit via a floating skimmer and is pumped into a hydrocyclone unit.
Centrifugal force drives oil to the centre of the hydrocyclone vortex and oil is removed via a small hole
in the end wall of the unit. The oil is then directed to a storage tank or drum.
This oil storage container has a large settling time where the oil floats to the top. Excess water is
drained from the bottom of the container back to the pit. The treated water is recycled through the
separator until it reaches a suitable standard for discharge to the sewer.
A hydrocyclone separator should be sized in accordance with the influent flow rate. The minimum size
is 1000 l/hr. An influent pit is used to allow sediments to settle. Skimmers should draw wastewater
from the surface of the influent pit. The equipment supplier/consultant should set an appropriate
recycle time to achieve an acceptable effluent quality.
Vertical Gravity Separator (VGS)
A vertical gravity separator operates by controlling fluid velocity and pressure allowing high density
contaminants to fall into a sump and oil droplets to rise.
As liquid enters the VGS, it flows up through a low pressure zone in the middle of a multi- leaved
spiral inverted V shaped baffle known as a spiral pack (SPAK). Free oil and impurities float to the
surface and overflow into a ‘slops tank’. This central low pressure zone creates a flow up through the
centre and down the inside of the main body.
As the fluid flows down the sides, due to numerous directional changes non-emulsified impurities fall
out of suspension and are drawn to the low pressure core. Heavy contaminants fall into a sump where
they can be drained off through a valve. Low density impurities move to the centre and rise to the
surface and overflow into the ‘slops tank’. Treated water flows from the ‘cleaned water outlet’.
The VGS should be sized according to the wastewater flow rate. Sizes range from 1000 to 3000 L/hr.
Maintaining Oil Separators
The manufacturers and or supplier should supply a comprehensive maintenance schedule for an oil
separator. However, there are some basic procedures common to all separators such as pumping out
the collection pit, drain and collect sludge from sumps, remove collected free oil, all of which must be
done by a licensed contractor. In addition all internal components must be cleaned and inspected for
serviceability and all electrical components must be inspected and serviced.
These devices should be maintained at a minimum four times a year (every 13 weeks).
Hawkesbury City Council
24
Liquid Trade Waste
Service Station Forecourts
•
Discharge of waste-water and run-off from service station refuelling areas may be permitted,
provided the business complies with the following pre-treatment requirements.
•
The forecourt area is to be swept prior to wash-down and any cleaning compounds must be
compatible with the waste-water pre-treatment system.
•
The forecourt area must be roofed and graded to exclude rainwater.
•
Waste-water must drain to a collection well. The collection well should have minimum capacity
of 750L and connected to an oil/water separator.
Stormwater Containment
Roofing of Liquid Trade Waste Generating Areas
Areas, where trade waste activities are carried out or pre-treatment equipment is installed, must be
roofed to prevent the ingress of rainwater from entering the sewerage system. For a structure where
one or more sides are open to the weather, the roof must overhang the containment area 10 degrees
from vertical. This is the minimum acceptable cover.
To ensure that no surface stormwater flows onto the process area, a bund/speed hump at least 50
mm high must be installed around the area as necessary. On the upper side of the area a strip drain
must be installed, however, this alone may not be adequate as stormwater may flood the drain and
flow onto the area. The overall surface water flow across the site has to be considered and the height
of the bund/speed hump adjusted.
Method of Exclusion of Stormwater
From a waste management point of view, the prevention of stormwater contamination is the preferred
solution. Areas that are likely to be contaminated should be bunded and covered with a roof. Spillage
of chemicals, products etc. should be recovered or cleaned by dry methods, so either system
sewerage or stormwater drainage is not contaminated.
Separation
Separation of dirty and clean areas is imperative for good waste management. Areas that are likely to
become contaminated are those areas where activities such as storage, handling or transferring of
liquid or solid materials occur.
Segregating clean and contaminated areas can be achieved by selective changes in surface
gradients, the use of speed humps or bunds or by the use of diversion and collection drains.
Bunding
The bund is designed to contain spillages and leaks from liquids used, stored or processed above
ground and to facilitate clean-up operations. As well as being used to prevent pollution of the
receiving environment, bunds are also often used for fire protection, product recovery and process
isolation.
Hawkesbury City Council
25
Liquid Trade Waste
Collection Drains
Collection drains should be constructed to ensure ease of inspection and cleaning. The grates should
be easy to remove and the pit should be wide enough so that accumulated solids can be easily
removed.
Diversion Drains
Diversion drains such as ‘spoon drains’ can be successfully used to divert stormwater away from the
contaminated area.
Speed Humps
Speed humps can be used to separate potentially contaminated areas from clean areas and a form of
containment where relatively small spills are likely to occur or a more substantial structure is not
practical.
Housekeeping practices for kitchen and oily waste
The cleaning frequency of a pre-treatment facility is governed by the quantity of accumulated waste; it
is therefore in the management’s interest to insure minimal waste is disposed through the facility.
If these suggestions are followed the pump-out frequency can be reduced, blockages in the drains
may be avoided and money can be saved. The correct management of liquid trade waste and proper
maintenance of pre-treatment facilities will result in a cleaner environment.
Kitchen Type Waste
•
•
•
•
•
•
•
•
•
•
•
•
Use water sparingly, efficiently, and recycle whenever possible.
Use aluminium foil to collect grease and oil spills around stoves, fryers, etc.
Use minimal grease and oil for cooking.
Use detergent sparingly.
Place screens on sink drains to keep solids from washing down the drain.
Scrape cooking utensils and plates before washing.
Place a container under the outlet of cooking vats used in barbeque charcoal rotisserie
appliances to collect fat.
Ensure the dishwasher is full every time it is used.
Use broom or mop for washing floors instead of the hose.
Rinse dishes in a plugged sink rather than under a running tap.
Do not put coffee grounds or tea leaves down the sink.
Collect oil and grease separately and dispose of separately by licensed recyclers.
Workshops, Garages, Service Stations
•
•
•
•
•
•
•
Ensure that the wash area is covered and bunded to secure all waste-water and connect all
drains to a pre-treatment facility.
Forecourt areas must be covered and graded to exclude stormwater.
Use water sparingly, dry sweep or clean before hosing.
Use ‘quick-break’ detergents. This will help capture more grease and petroleum hydrocarbons
in the oil/water separator.
Use cleaning products that have a pH range of 7-10. Metal salts can ionise if the pH of the
waste is higher or lower. In this form they are very difficult to remove without expensive pretreatment.
If parts are washed in a solvent cleaning bath, it should be done in a closed recycle system.
Use drip trays to catch oil.
Hawkesbury City Council
26
Liquid Trade Waste
•
•
•
•
Drain oil and fluids from engines, gearboxes, and other parts into storage containers
before dismantling.
Do not discharge caustic bath and rinse into the sewerage system.
Store oil, solvents, cleaning products and other chemicals in bunded areas not
connected to the sewerage system.
Arrange for collection of oils, grease and solvents for recycling by licensed contractors.
Hawkesbury City Council
27
Liquid Trade Waste
Glossary
Glossary
28
Biochemical Oxygen Demand (BOD5): The amount of oxygen required for the biochemical
degradation of organic material in wastewater over a period of five days at 20 C. In practical terms,
BOD is a measure of biodegradable organic content of the waste.
Biosolids: Primarily organic solid product produced by sewage processing. Until such solids are
suitable for beneficial use, they are defined as wastewater solids or sewage sludge.
Bunding: Secondary containment provided for storage areas, particularly for materials with the
propensity to cause environmental damage.
Chemical Oxygen Demand (COD): A measure of oxygen required to oxidise organic and inorganic
matter in wastewater by a strong chemical oxidant. Wastewaters containing high levels of readily
oxidised compounds have a high COD.
Clean Dry Trades: Are generally defined as those where showers are not provided on the premises.
Commercial Kitchen/Caterer: For the purpose of this Policy, a commercial kitchen is a premises that
is typically a stand-alone operation and prepares food for consumption off-site. These types of
businesses typically cater to wedding functions, conferences, parties, etc. This definition would not
apply to a food processing factory supplying pre-prepared meals to an airline company or similar.
Contingency Plan: A set of procedures for responding to an incident that will affect the quality of
liquid trade waste discharged to the sewerage system. The plan also encompasses procedures to
protect the environment from accidental and unauthorised discharges of liquid trade waste to the
stormwater drainage system, and leaks and spillages from stored products and chemicals.
Dirty Dry Trades: Are generally defined as those where showers are provided on the premises.
Domestic Sewage: The waterborne waste derived from human origin, comprising faecal matter,
urine and liquid household wastes from water closet pans, sinks, baths, basins and similar fixtures
designed for use in private dwellings, but excludes septic waste or pan contents.
Due Diligence Program: A plan that identifies potential, health and safety, environmental or other
hazards (e.g. spills, accidents or leaks) and appropriate corrective actions aimed at minimising or
preventing the hazards.
Effluent: The liquid discharged following a wastewater treatment process.
Effluent Improvement Plan (EIP): The document required to be submitted by a discharger who is
not meeting the acceptable limits for discharge waste quality set down in Council's approval
conditions and/or liquid trade waste agreement. The document sets out how a discharger will meet
the acceptable limits for the discharge of liquid trade waste to the sewerage system within a given
timeframe.
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Heavy Metals: Metals of high atomic weight which in high concentrations can exert a toxic effect and
may accumulate in the environment and the food chain. Examples include: mercury, chromium,
cadmium, arsenic, nickel, lead and zinc.
Housekeeping: is a general term, which covers all waste minimisation activities connected with the
way in which operations within the premises are carried out.
Industrial Discharges: Industrial liquid trade waste is defined as liquid waste generated by industrial
or manufacturing processes.
Large Fast Food Outlet: A food business that typically discharges more than 5 kL/d. Premises of this
nature include K.FC, McDonalds, Red Rooster, Pizza Hut, Hungry Jack's and Burger King.
Local Government Regulations: Regulations under the Local Government Act 1993, including the
Local Government (General) Regulation 2005,
Liquid Trade Waste: The liquid wastes discharged to the sewerage system from any business, trade
or manufacturing premises
Methylene Blue Active Substances (MBAS): These are anionic surfactants (see Surfactants
definition) and are called MBAS as their presence and concentration is detected by measuring the
colour change in a standard solution of methylene blue dye.
Minimal Pre-treatment: For the purpose of this Policy includes: sink strainers, dry basket arrestors,
plaster arrestors and fixed or removable screens.
Open Area: Any unroofed process, storage, washing or transport area potentially contaminated with
rainwater and substances, which may adversely affect the sewerage system or the environment.
pH: A measure of acidity or alkalinity of an aqueous solution, expressed as the logarithm of the
+
reciprocal of the hydrogen ion (H ) activity in moles per litre at a given temperature; pH 7 is neutral,
below 7 is acidic and above 7 is alkaline.
Premises: Has the same meaning as defined in the Local Government Act Dictionary and includes
any of the following:
a)
b)
c)
d)
e)
f)
g)
a building of any description or any part of it and the appurtenances to it;
land, whether built on or not;
a shed or other structure;
a tent;
a swimming pool;
a ship or vessel of any description (including a houseboat); or
a van.
Prescribed Pre-treatment Equipment: is defined as standard non-complex equipment used for pretreatment of liquid trade waste prior to being discharged to the sewerage system (e.g. a grease
arrestor, an oil/water separator, solids arrestor, cooling pit).
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Sewerage System: The network of sewage collection, transportation, treatment and by-products
(effluent and biosolids) management facilities.
Surfactants: The key active ingredient of detergents, soaps, emulsifiers, wetting agents and
penetrants. Anionic surfactants react with a chemical called methylene blue to form a blue-chloroformsoluble complex; the intensity of colour is proportional to concentration.
Surge Control Device: A device that is installed in a grease arrestor chamber and may improve the
arrestor performance by stabilising hydraulic surges.
Suspended Solids (SS): The insoluble solid matter suspended in wastewater that can be separated
by laboratory filtration and is retained on a filter; previously also referred to as non-filterable residue
(NFR).
Total Dissolved Solids (TDS): The dissolved salts in wastewater.
Waste Minimisation: Procedures and processes implemented by industry and business to modify,
change, alter or substitute work practices and products that will result in a reduction in the volume
and/or strength of waste discharged to sewer.
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HAWKESBURY CITY COUNCIL
Liquid Trade Waste – Discharge Categories and Management Guidelines