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The maximum quantity of trade effluent proposed for production in one day ... Only those elements of the formula that apply to the type of treatment ... – PowerPoint PPT presentation

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  • Workshop 6
  • Effluent Treatment
  • 28th February 2008

Welcome to the Workshop
  • Nigel Leehane,
  • Envirowise

Workshop 6Effluent Treatment
  • Consented discharges
  • Water resource protection
  • Effluent Treatment

Consented Discharges
  • Nigel Leehane, Envirowise

Water Industry Act Part 4 Sewerage Services
  • Trade Effluent Consent
  • The occupier of any trade premises can discharge
    any trade effluent into a public sewer providing
    they have the sewerage undertakers consent.
  • Application for consent must provide details of
  • nature or composition of the effluent
  • maximum quantity of the effluent to be discharged
    on any one day and
  • highest rate at which the effluent will be
  • The sewerage undertaker can refuse consent, or
    grant consent with or without conditions.

Consent conditions
  • The conditions can include requirements relating
    to any of the following
  • periods of discharge
  • exclusion from the effluent of all condensing
  • elimination or diminution of any specified
  • temperature, acidity or alkalinity
  • payment for the reception of the effluent and for
    its disposal
  • provision and maintenance of chambers or manholes
    for sampling
  • testing and maintenance of any meters required to
    measure the volume and rate of discharge
  • testing and maintenance of apparatus for
    determining the nature and composition of any
    trade effluent discharged
  • keeping of records
  • making of returns.

Trade effluent agreements
  • Under Section 129, a sewerage undertaker may
    enter into and carry into effect-
  • an agreement with the owner or occupier of any
    trade premises within its area for the reception
    and disposal by the undertaker of any trade
    effluent produced on those premises
  • This generally applies where the undertaker has
    to construct, modify or extend a sewage treatment
    works, so the agreement addresses the financial
  • The Act allows the undertaker to authorise the
    discharge by means of the agreement, rather than
    requiring a separate consent.

Water UK
  • Water UK is the industry association that
    represents UK statutory water supply and
    wastewater companies at national and European
  • In January 2008 Water UK released general
    procedures for water and sewerage companies to
    use in operating trade effluent consents. They
    also produced guidance concerning control and
    charging. These procedures meet the requirements
    of relevant legislation.
  • The guidelines apply to all trade effluent
    discharges except
  • Discharges under existing agreements, until they
    can be terminated
  • Discharges under existing consents, until they
    can be terminated
  • Discharges of radioactive substances

Guidelines for issue of trade effluent consents
  • Discharge of trade effluent to the sewerage
    system can only occur with the sewerage companys
    (and possibly EAs) consent. Consents are in
    place to prevent trade effluent discharges from
  • Damage or harm to the sewerage system and
    personnel employed in them
  • Interference with the effective and economic
    treatment at the sewage treatment works
  • The products of treatment to have unacceptable
    effects on water resources or the environment
  • Unacceptable storm sewage discharges to
  • Installations under the PPC regulations
    special category effluent are subject to dual
    control of the sewerage undertaker and the EA

Consents continued
  • The consent conditions should also encourage all
    practical means of a reduction at source of the
    volume and polluting characteristics of the
  • Consent conditions do not exclude the possibility
    of the customer pre-treating trade effluent. For
    example they may consider it economically viable
    to pre-treat their effluent to reduce the
    payments for subsequent treatment.
  • The customer may be required to keep records of
    volume, rate of discharge and nature and
    composition of effluent discharged.

Information required
  • Information concerning the possible pollutants
    found in the discharge is required by the
    sewerage provider prior to agreeing a consent.
    Some of this information is required by law.
  • A pre-assessment may be conducted. It is likely
    that this would involve the customer highlighting
    all the substances that they are likely to
    produce that feature on the list of most
    polluting substances.
  • These substances include but are not limited to
  • Chromium
  • Copper
  • Arsenic
  • pH outside 5.5-9
  • Benzene
  • PAHs
  • Dioxins
  • Chloroform
  • BTEX
  • Permethrin
  • Simazine
  • 1,1,1-trichloroethane

Information required
  • The assessment itself will involve completing a
    form that provides further information about the
    pollutants to be discharged. The minimum
    information required will be
  • The legal entity of the occupier of the trade
    premises who seeks consent
  • The nature and composition of the trade effluent
  • The maximum quantity of trade effluent proposed
    for production in one day
  • The highest rate at which it is proposed to
    discharge the trade effluent
  • It is also likely that information concerning the
    water supply to the premises and the use of fresh
    water will be required prior to the consent being

  • Charging should recover the costs of treating and
    disposing of trade effluent based on estimates of
    expenditure (Mogden calculation)

Calculating the Mogden Formula
  • Total flow and load of sewerage reaching the
    undertaker should be taken from an average of
    best available data.
  • Fixed costs of the sewerage system are recovered
    as part of a standing charge which is usually
    included in R.
  • The unit cost for V is from costs associated with
    pumping stations, inlet works, primary settlement
    units, treatment for reducing concentrations of
    residual suspended solids and all outfalls for
    treated sewage.
  • B is derived from costs associated with
    biological filtration plants, activated sludge
    plants and final settling tanks and the
    proportion of total sludge treatment and disposal
    costs associated with disposal of secondary
    sludge treatment and disposal.

Calculating the Mogden Formula
  • S is taken from costs associated with pumping
    sludge to treatment and sludge dewatering and
  • Charges for sea outfalls are included in R, Vm
    and M.
  • A minimum charge can be applied where effluent is
    very weak. Individual sewerage undertakers can
    determine at what result of the mogden formula
    the minimum charge will apply.
  • Only those elements of the formula that apply to
    the type of treatment undertaken on the effluent
    produced by the customer are applied to calculate
    the charges.

  • Frequency of sampling for charging purposes
    should be based on a reasonable compromise
    between cost of sampling and analysis in relation
    to total discharge costs recognising size and
    variability of discharge.
  • The oxidation charge from the sewerage undertaker
    should be based on COD. The quantity of primary
    and secondary sludge produced by the biological
    oxidation process in the treatment works is
    directly related to the oxidation load and
    therefore customers are required to pay in
    relation to the quantity of each their effluent
  • Toxic substances should not be charged for as the
    consent should restrict their discharge to the
    level at which satisfactory treatment can be

Special category effluent
  • Where a sewerage undertaker is proposing to enter
    into an agreement for the reception or disposal
    of any special category effluent, it shall be the
    duty of the undertaker to refer to the
    Environment Agency the questions
  • whether the operations should be prohibited
  • if they are not prohibited, should conditions be
  • The undertaker should not issue a consent until
    the Agency serves notice of its determination
  • Under Section 135a, the Environment Agency can
    issue a notice requiring the submission of
    information regarding special category effluent

Meaning of 'special category effluent'
  • Under Section 138, trade effluent shall be
    special category effluent if
  • substances prescribed under this Act are present
    in the effluent or are present in the effluent in
    prescribed concentrations
  • the effluent derives from any prescribed process
    or from a process involving the use of prescribed
    substances or the use of such substances in
    quantities which exceed the prescribed amounts
  • This does not apply to permitted PPC
  • Trade Effluents (Prescribed Processes and
    Substances) Regs include
  • Schedule 1 Red List Substances
  • Schedule 2 Prescribed Processes

Discharge to surface and groundwaters
  • Part 3 of the Water Resources Act 1991 classifies
    the following as controlled waters
  • relevant territorial waters
  • coastal waters
  • inland freshwaters, which are the waters of any
    relevant lake or pond, or of any relevant river
    or watercourse
  • groundwaters, which are any waters contained in
    underground strata.
  • Under Section 85 of this Act, a consent is
    required from the Environment Agency to allow
  • poisonous, noxious or polluting matter or any
    solid waste matter to enter any controlled

Pollution offences
  • A person contravenes Section 85 if he causes or
    knowingly permits any poisonous. noxious or
    polluting matter or any solid waste matter to
    enter any controlled waters.
  • Under Section 88, an offence has not been
    committed if the discharge is in accordance with
  • A discharge consent
  • A PPC permit
  • A waste management license
  • Various other permits
  • Prohibition by notice
  • Enforcement notices

Water Resource Protection
  • Nigel Leehane, Envirowise

Water resource protection through pollution
  • Source Pathway Receptor
  • Chemicals Leaks from Local river
  • from your site the drainage pond, aquifer
  • system
  • Water resource protection relies on preventing
    pollution, so that there is no pathway between
    the source and the receptor.

Pollution prevention
  • Industries regulated under the PPC system are
    required to demonstrate that they are using Best
    Available Techniques (BAT) to protect water
    resources from their activities
  • BAT is appropriate for use by all industrial and
    commercial sites
  • BAT considers
  • Subsurface structures drainage systems,
    underground pipes, sumps, underground storage
    vessels, soakaways
  • Surfacing
  • Above-ground storage tanks - including bunds and
    containment kerbs
  • Storage areas

Subsurface structures - mapping
  • Understand site drainage systems
  • Map drainage and subsurface pipework
  • Identify surface water soakaways, sumps and
    drainage vessels
  • Identify routes for pollutants to enter drains
  • Identify options to prevent pollutant releases
    into and from drains
  • Colour code site drains
  • Clearly identify foul drains, surface water
    drains, drains to ETP
  • BAT is red for foul drains and blue for surface
  • Ensure maps and plans are kept up to date

Subsurface structures
  • Protect sources through pollution prevention
  • Engineer systems to minimise leakages
  • Put in place a detection system, particularly
    where hazardous substances are involved
  • Install secondary containment for underground
    storage vessels, sumps and pipework
  • Sumps should
  • Be impermeable and resistant to stored materials
  • Have any contents regularly removed and checked
    for contamination
  • Be fitted with a high level probe and alarm when
    not regularly inspected
  • Be subject to inspection, including water testing
    where integrity is in doubt

  • Design of surfaces, containment and drainage
    facilities for all operational areas should
  • Operational areas should have in place or, if not
    present, should set up an improvement plan to
  • An impervious surface
  • Spill containment kerbs or bunds
  • Sealed construction joints
  • Connection to a sealed drainage system
  • Permeability
  • Resistance to chemical attack
  • Maintenance and inspection procedures
  • Collection capacities
  • Surface thickness
  • Strength/ reinforcement
  • Materials of construction

Above ground storage tanks and bunds
  • Bunds should be provided for all above ground
    storage tanks containing liquid that could be
    harmful to the environment. Bunds should
  • Be impermeable and resistant to the stored
  • Have no outlet and drain to a blind collection
  • No penetration of bund by pipes or ducts
  • Have a 110 capacity of the largest tank, or 25
    of total tankage, which ever is greater
  • Be regularly inspected and any contents removed
    or fitted with a level probe and alarm. Water
    test where integrity is in doubt
  • Have fill points within the bund

Storage areas
  • Storage areas for IBCs, drums and bags
  • Should be located away from watercourses and
    sensitive boundaries and protected against
  • Provide adequate facilities for substances with
    special requirements, e.g. flammable or heat
  • Ensure storage areas are clearly marked and
    maximum capacities are not exceeded
  • Provide procedures to keep incompatible
    substances apart e.g. pure and waste products
  • Lids, caps and valves should be secured and in
    place, including empty containers
  • At least weekly inspection should occur
  • Ensure a procedure is in place to deal with
    damaged or leaking containers

  • Regularly inspect and maintain impervious
    surfaces, kerbs, bunds and subsurface structures
    including sumps and drainage systems.
  • Underground inspection can use
  • Pressure tests
  • Leak tests
  • Material thickness checks
  • CCTV
  • Ensure drainage system can cope with chemicals
    used for cleaning

Source protection through pollution prevention
  • Prevent spills and other accidents
  • Provide general environmental awareness training
  • Provide chemical spill kits and training in use
  • Ensure procedures for handling, offloading,
    moving chemicals and other potential pollutants
    are in place and up to date
  • Reduce potential impacts of accidents
  • Procedures for managing chemical, raw material
    and product spills
  • Plan for management of firewater

Pollution Prevention Guidance
  • The Environment Agency maintains a series of
    Pollution Prevention Guidance Notes (PPGs).
  • These apply to all sites not just PPC permitted
  • Adhering to the guidance provided may provide
    some degree of defence in the event of an
    incident resulting in prosecution
  • There are guides for both - issues (e.g. design
    of oil separators)
  • - sectors (e.g. agriculture)
  • These can be found at
  • http//www.netregs.gov.uk/netregs/resources/278006

PPGs by Sector
  • Agriculture Leather
  • Chemicals Manufacture Metals and Machinery
  • Construction Non-metallic minerals
    Electronics Pulp and Paper
  • Fishing and Aquaculture Printing and Publishing
  • Food and Drink Recorded Media
  • Forestry Rubber and Plastic Products
  • Hotels and Restaurants Textiles and Clothing
  • Hunting Wood Products

PPGs by Issue
  • PPG 1 - General guide to pollution prevention and
  • PPG 2 - Above ground oil storage tanks
  • PPG 3 - Use and design of oil separators in
    surface water drainage systems
  • PPG 4 - Treatment and disposal of sewage where no
    foul sewer is available
  • PPG 5 - Works and maintenance in or near water
  • PPG 6 - Working at construction and demolition
  • PPG 7 - Refuelling facilities
  • PPG 8 - Safe storage and disposal of used oils
  • PPG 10 - Highway depots
  • PPG 13 - Vehicle washing and cleaning
  • PPG 14 - Marinas and crafts

PPGs by Issue
  • PPG 17 - Dairies and other milk handling
  • PPG 18 - Managing fire water and major spillages
  • PPG 19 - Garages and vehicle service centres
  • PPG 20 - Dewatering underground ducts and
  • PPG 21 - Pollution incident response planning
  • PPG 22 - Dealing with spillages on highways
  • PPG 23 - Maintenance of structures over water
  • PPG 24 - Stables, kennels, catteries
  • PPG 25 - Hospitals and health care establishments
  • PPG 26 - Storage and handling of drums and
    intermediate bulk containers (IBCs)
  • PPG 28 - Controlled burn

  • The first in the series that provide practical
    advice on how to avoid causing pollution,
    minimise waste and comply with legislation.
  • The guide gives a brief introduction to the areas
    covered by the series
  • Legal framework
  • Site drainage
  • Waste storage and disposal
  • Deliveries and security
  • Oil storage and pipelines
  • Contingency plans
  • Construction and demolition
  • Agriculture
  • Groundwater pollution

PPG3 Use and design of oil water separators
  • Oil separators are fitted to drainage systems to
    remove and retain oil. They should be installed
    at any site that does not have SUDS (Sustainable
    Drainage System) and is at risk from oil
  • The PPG provides guidance on selecting the most
    appropriate category of separator (class 1 to
    discharge 5mg/l oil or class 2 to discharge
    100mg/l). It explains the difference between full
    retention, bypass and forecourt separators and
    describes how to calculate the size of separator
  • Advice concerning alarms, closure devices and
    labelling is provided. Maintenance of the oil
    water separator is important to ensure it
    continues to operate effectively. Disposal of the
    oil as hazardous waste is required and the
    legislation governing this is referenced.
  • A Pollution Incident Response Plan (PIRP) should
    include all separators but they should not be
    used as the primary method of controlling large

PPG5 Works and maintenance in or near water
  • Includes any activity that may affect the bed or
    banks of any watercourse or wetland. The guide
    highlights the importance of planning as most
    accidents can be avoided. More formal planning
    requirements such as Environmental Impact
    Assessments and SUDS are also outlined.
  • The guidance considers different forms of
    pollution likely to be caused and the best
    methods of planning for and controlling the
  • Silt
  • Concrete and cement
  • Oil and chemicals
  • Bridge maintenance and structures over water
  • Herbicide use
  • Waste management considerations, including a
    checklist for a site waste management plan are
    included along with information for an Incident
    Response Plan

PPG13 Vehicle washing and cleaning
  • Run-off from vehicle washing is considered trade
    effluent. Ensure that it is discharged only in to
    foul sewerage drainage systems rather than
    surface water systems. An agreement with your
    sewerage provider must be reached prior to
  • This guidance describes the requirements of
    vehicle washing activities including
    consideration of reducing, reusing, recycling
    wash water and dealing with storage and spills of
  • Good practice for different washing techniques is
    included. High pressure wash systems use large
    amounts of water and if cleaning yards or other
    equipment with them, run-off must be prevented
    from entering surface water drainage systems.
    Washing by hand, automatic systems and water free
    systems are also considered.

PPG21 Pollution Incident Response Planning
  • Pollution Incident Response Plans are designed to
    prevent and mitigate damage to the environment
    caused by accidents such as spills and fire.
  • The site drainage plan should provide
  • Details of the site
  • Emergency contacts
  • A comprehensive drainage plan showing foul
    drains, surface water drains, emergency service
    access, storage areas and bunds etc.
  • Chemical, product and waste inventory
  • Emergency procedures including fire fighting
    strategy, methods for alerting nearby properties
    and procedures for containing leaks and spills.
  • Staff training, including practice exercises, is
    important to ensure success of the plan. It
    should be distributed to all relevant parties and
    kept up to date.

PPG26 Storage and handling of drums and IBCs
  • Applies to containers of lt1000 litres that are
    not directly connected to a part of the process.
    PPG2 applies to fixed containers.
  • Drums containing substances that are flammable,
    hazardous, pesticides or timber treatment
    products are governed by specific legislation
    which is described.
  • Most accidents occur during the delivery and
    handling stages and specific areas should be
    marked out and surface water drains protected
    from runoff. Staff training and supervision of
    deliveries is also recommended.
  • Primary containers and secondary containment
    systems are discussed, in particular their
    siting, capacity, design, construction and
    maintenance. Methods of dealing with spills and
    waste management guidance are provided.

Use your EMS for pollution prevention
EMS elements
Water efficiency campaign
Resources, roles responsibilities
Responsibilities for process management, water
Competence, training
Spill response training, awareness-raising
Operational controls
Handling procedures, preventative maintenance
Monitoring and measurement
Inspections, monitoring discharges
Internal audit programme
Check adherence to procedures, levels of
competence, etc
Effluent Treatment
  • Gwenda McIntyre, Envirowise

Effluent Treatment Technologies
  • Gwenda McIntyre, Envirowise

Effluent treatment technologies
  • Envirowise Guides
  • GG109 Choosing cost-effective pollution control
  • GG37 Cost-effective separation technologies for
    minimising wastes and effluents
  • GG54 Cost-effective membrane technologies for
    minimising wastes and effluents
  • GG175 Improving the performance of effluent
    treatment plant
  • All currently under review for re-issue
    available from Envirowise archives

Effluent treatment technologies
  • Pollutants
  • Pollutants are substances that have the potential
    to have negative effects on the natural
    environment, to cause damage to infrastructure or
    harm to human health.
  • Pollutants in industrial wastewater contain a
    mixture of organic and inorganic substances, in
    solution, as solids in suspension, as a separate
    phase (e.g. an oil layer) and as colloidal matter
    (e.g. starch or clay)

Effluent treatment technologies
  • Pollutants continued
  • Some pollutants are toxic and/or harmful and can
    have a direct impact on the receiving environment
    e.g. heavy metals, mineral oils, solvents, strong
    acids and alkalis.
  • Other pollutants are non-toxic and not directly
    harmful but their presence can have indirect
    negative effects e.g. beer, milk, clays and
    agricultural land run-off.

Effluent treatment technologies
  • Pollutants continued
  • Pollutants which are indirectly harmful cause
    negative impacts in various ways
  • Placing an oxygen demand on the receiving water
  • Causing eutrophication
  • Preventing light ingress, inhibiting
  • Creating a barrier to oxygen transfer
  • Physically blocking fish gills and preventing
  • Coating wildlife with oils
  • High temperature discharges can also have an
    impact and can therefore be polluting.

Effluent treatment technologies
  • Measuring and monitoring pollutants
  • Most pollutants exert an oxygen demand on a
    receiving water
  • Chemical oxygen demand COD
  • Biological oxygen demand BOD
  • COD is measured chemically samples are digested
    in hot concentrated potassium dichromate solution
    for 2 hours.
  • Potassium dichromate contains chromium VI a
    powerful oxidant.
  • Chromium VI oxides most organic and some
    inorganic substances in the sample and is reduced
    to chromium III.
  • The extent of oxidation is measured (usually by
    colour change).
  • Most organics and some inorganic species in the
    sample will be oxidised.

Effluent treatment technologies
  • Measuring and monitoring pollutants continued
  • COD values provide an indication of the total
    pollutant load in an effluent hence COD limits
    are imposed on most consented discharges
  • COD does not
  • Measure levels of inert polluting materials e.g.
  • Differentiate between pollutants
  • Measure all important dissolved pollutants e.g.
    ammonia, phosphate
  • Some chemicals interfere with COD measurement
  • Strong oxidants and reducing agents e.g.
    peroxides, chlorine species
  • High halide levels e.g. chloride briny or salt
    water needs special treatment
  • COD measurement cannot easily be performed

Effluent treatment technologies
  • Measuring and monitoring pollutants continued
  • Total organic carbon (TOC) may be substituted for
    COD analysis for monitoring the organic pollutant
    level in discharges and process waters where
  • Operators can establish and demonstrate a
    consistent relationship between TOC and COD for
    the effluent stream
  • For an organic waste stream containing simple
    sugars only
  • TOC in mg O2/litre 12/32 COD
  • TOC analysers can be operated to take
    measurements every few minutes 24 hours/7days a
  • Some down time cleaning, maintenance,
  • Need a supply of chemicals (acid, alkali and
  • Samples are digested thermally or chemically
    (UV/persulphate or ozone) and emitted CO2
    measured by infra-red

Effluent treatment technologies
  • Measuring and monitoring pollutants continued
  • Biological oxygen demand BOD
  • BOD reflects the oxygen demand an effluent places
    on the natural environment i.e. the receiving
    waters or the biotreatment units in an effluent
    treatment works
  • BOD consents are often set for
  • Discharges to surface waters
  • Trade effluents to sewer for downstream
    biological treatment
  • BOD is the oxygen consumed by sewage acclimatised
    microbes in aerobically digesting a sample of the
  • Test period affects results
  • BOD28 28 day BOD test
  • BOD5 5 day BOD test
  • Time taken to digest sample indicates how readily
    sample will degrade

Effluent treatment technologies
  • Measuring and monitoring pollutants continued
  • Biological oxygen demand BOD
  • Comparison of BOD and COD values indicates
  • How readily biodegradable an effluent is likely
    to be
  • The time profile of the likely impact on oxygen
    levels in receiving waters
  • How easy it will be to treat the effluent using
    typical biological treatment processes
  • Domestic sewage effluents have a BOD5/COD ratio
    of gt0.5 and a BOD28/COD ratio 1
  • Effluents with a BOD5/COD ration of gt0.5 are
    considered readily treatable in conventional
    biotreatment units

Effluent treatment technologies
  • Pollutant removal
  • Pollutants which cause harm through preventing
    oxygen transfer or preventing photosynthesis
    oils and suspended solids and colloidal
    substances (fibres, silts, clays)
  • Must be removed before release of water to
    natural environments
  • Must be removed before release of water to
    biological treatment plant

Effluent treatment technologies
  • Pollutant removal continued
  • Oils and other free organic phases e.g. solvents
    or diesel, removed by
  • Phase separation e.g. skimming, interceptors
  • Vacuum, steam or air stripping of volatile
  • Solids/colloids removed by
  • Screening coarse solids
  • Degriting heavy/large solids
  • Settlement/floatation
  • With/without chemical coagulation and
    flocculation e.g. clarification or dissolved air
  • Filtration e.g. membranes, sand filters, filter

Effluent treatment technologies
  • Clarifiers are very commonly used in wastewater
    treatment applications.
  • Clarification allows solid material to be
    separated from liquid by settlement with or
    without chemical coagulants to enhance
  • Clean water from the clarifier is recycled back
    to be used as primary wash-water in many

Standard clarifiers
Lamella clarifiers
Effluent treatment technologies
  • Dissolved air flotation DAF
  • Another form of clarification using fine air
    bubbles to float solids and oils to the surface
    for skimming and removal.
  • Addition of flocculation and coagulation aids to
    effluent enhances colloidal and dissolved
    pollutant removal.

Mechanical skimmer for removal of floating sludge
Waste sludge
Fine bubble formation zone
Sludge rising
Treated effluent inlet
Compressed air
Clarified water for re-use
Clear effluent return line
Pump and compressed air injection
Effluent treatment technologies
  • Pollutant removal continued
  • Dissolved pollutants can be removed by
  • Precipitation
  • Membrane filtration
  • Electrolytic separation
  • Ion exchange
  • Adsorption
  • Air and steam stripping
  • Evaporation and distillation
  • Chemical oxidation
  • Biological oxidation or reduction

Effluent treatment technologies
  • Precipitation
  • Chemical addition to the effluent to reduce the
    solubility of pollutant species
  • Addition of ferric salts to precipitate out
    phosphates as iron phosphate
  • Addition of acid/alkali to alter pH and
    precipitate metals as oxides and hydroxides
  • Lime, magnesium hydroxide, caustic
  • Hydrochloric acid
  • Removal of solids by settlement or floatation
    (clarification) or filtration
  • Removal of solids in secondary treatment stage
    e.g. within an activated sludge biotreatment unit
  • Consider impact on sludge disposal/recovery

Effluent treatment technologies
  • Membrane filtration
  • Membrane provides semi-permeable barrier
  • Allows selective passage of pollutants through
  • Permeate cleaned water
  • Retentate concentrated pollutants
  • Types
  • Reverse osmosis
  • Nano-filtration
  • Ultrafiltration
  • Microfiltration

Increasing selectivity and cost
Envirowise guide GG54 Cost effective membrane
technologies for minimising wastes and effluents
Effluent treatment technologies
  • Membrane filtration continued
  • Membranes may be applied on process waters or
    final waste streams
  • For recovery of materials use in process is
  • Pre and post-treatment may be required
  • Reverse osmosis is usually preceded by
    ultrafiltration to avoid blockages

Water for re-use
Process effluent
Materials recovery
Concentrate (retenate)
Envirowise guide GG54 Cost effective membrane
technologies for minimising wastes and effluents
Effluent treatment technologies
  • Electrolytic separation
  • Removal of metals from solution by deposition on
    a conducting surface (electrode)
  • High surface area electrode maximises treatment
  • Packed or reticulated bed electrodes
  • Generally applied in concentrated waste streams
    for recovery of metals e.g. electroplating works
  • Electrodialysis combines electrolysis and
    membrane technology

_ _ _ _ _ _ _ _ _ _ _ _

Treated stream

Effluent treatment technologies
  • Ion exchange
  • Exchange of ions with a pre-charged resin/zeolite
    for removal of pollutants and recovery or
  • Used in metal finishing industry, photographic
    processing, textile manufacture
  • Metals/anions recovered in solution during
    regeneration of resin
  • Used on concentrated process streams
  • Pre-filtration may be required to avoid blockage
  • Electrochemical ion exchange EIX
  • Enhanced ion exchange, uses electrical energy to
    drive process
  • Limits chemical requirements

Effluent treatment technologies
  • Air and steam stripping
  • Air and steam stripping used to remove volatile
    components dissolved and free phase from water
    or other contaminated media e.g. soil
  • For water treatment
  • Packed towers
  • Spray towers
  • Air sparging in a stripping basin
  • VOCs are volatilised and transferred to air/steam
    phase for recovery

Effluent treatment technologies
  • Adsorption
  • Adsorbent substance placed in flow of
    effluent/process water
  • Activated carbon, chitin, other adsorbent
  • Adsorbent bed taken offline when breakthrough
  • Adsorbent may be thermally or chemically
    regenerated and substances may be recovered
  • Widely used in water treatment and also in
    process industries for e.g. decolourising sugar
  • Most effective when other pollutant levels are
  • May require pre-treatment to remove suspended
    solids and colloidal matter
  • Consider logistics adsorbent material volumes
    may be considerable

Effluent treatment technologies
  • Evaporation and distillation
  • Couples heat and low pressure to remove water and
    volatile components from process effluent
  • Selective condensing allows separation of clean
    water and any volatile components
  • Remaining materials may be recovered or disposed
  • Used in the concentration of effluents prior to
    disposal e.g. recovery of water from water based
    metal working fluids
  • Concentration of waste stream reduces disposal
    costs with recovery of water
  • Energy costs are significant hence most
    application where significant materials recovery
    is achievable

Effluent treatment technologies
  • Chemical oxidation
  • Chemical oxidation processes employ free radical
    oxidation processes to breakdown pollutants to
    make them more readily biodegradable
  • Free radical oxidation processes mimic the
    natural processes occurring in air and water
    which remove pollutants
  • Systems based on
  • Iron/hydrogen peroxide combinations (Fentons)
  • Sunlight/titanium dioxide/peroxide/ozone
  • UV light/peroxide/ozone combinations

Increasing operations costs
Effluent treatment technologies
  • Chemical oxidation
  • Widely used in removal of trace contaminants from
  • Pesticides removal from ground and surface water
    for potable use
  • Tertiary treatment of sewage effluent for removal
    of dye colour
  • Main uses pre-treatment of concentrated
    wastewater and site remediation
  • Not usually applied to materials recovery, other
    than water

Hydrogen peroxide and/or ozone injection
Treated effluent
UV system
Recycle loop
Effluent treatment technologies
  • Biological treatment
  • Biological treatment of organic pollutants
  • Aerobic oxidation creates carbon dioxide CO2,
    water and biomass
  • Anaerobic reduction creates methane (CH4) and
    hydrogen (H2) biogas
  • Biological treatments are considered the Best
    Available Techniques (BAT) for treatment of
    biodegradable pollutants
  • Sewage treatment works which accept trade
    effluents generally use biological treatment with
    pre- and post-treatment as necessary e.g. for
    solids removal, pH adjustment and nutrients

Effluent treatment technologies
Typical sewage treatment works technologies
Separation of excess hydraulic load for
stormwater discharge/treatment
Grit removal
Primary settlement/sedimentation
Secondary biological treatment
Secondary settlement
Excess biosolids
Tertiary treatment
Sludge treatment and disposal
Surface water discharge
Effluent treatment technologies
Typical sewage effluent characteristics at
various treatment stages
  • COD BOD SS NH3 (N) PO4 (P)
  • 600 300 500 40 -
  • 300 150 150 50 -
  • 100 20 20 50 3-14
  • 15 lt5 lt5 10-15 1-2

Levels in mg/l
Effluent treatment technologies
  • Biological treatment systems aerobic
  • Disperse growth activated sludge, oxidation
    ditch, sequential batch reactors (SBR), membrane
    bioreactors (MBR)
  • Fixed film Submerged aerated filters (SAF),
    biological aerated flooded filters (BAFF),
    rotating biological contactors (RBC), trickle
    filters, packed towers
  • Oxygen supply air or pure oxygen
  • Aeration systems - mechanical mixing and sparge
  • Microbe populations establish with time, impacted
  • Conditions - natural and operational,
  • Changes in effluent flow, composition,
  • Disperse systems need return of some solids to
    maintain population
  • Fixed films need periodic cleaning to reduce
    biofilm build-up
  • Biosolids created require treatment and

Effluent treatment technologies
  • Biological treatment systems anaerobic
  • Disperse growth anaerobic contactors
  • Fixed film anaerobic filters, upflow anaerobic
    sludge blanket (UASB)
  • Batch and continuous systems
  • Heat required mesophilic and thermophilic
    digestion stages
  • Post-treatment effluent and sludge stabilisation
    temperature drop, oxygen sparge or re-aeration
  • Off-gases flammable, explosive, toxic and
    potentially corrosive
  • Methane, hydrogen, hydrogen sulphide
  • Off-gases require capture, treatment and flaring
    or storage and re-use
  • Biogas can be re-used on-site or sold heat and
  • Anaerobic systems sensitive to certain pollutants
    certain detergents and metals can inhibit
  • Often applied in sequence with aerobic treatment

Effluent treatment systems
  • Sludge treatment
  • Conventional sewage treatment produces sludges
  • Primary sludges screens, detritors and primary
  • Secondary sludges excess biosolids from
    biotreatment units
  • Tertiary solids fine biosolids
  • Sludges require
  • Screening, conditioning, thickening, stabilising
    for economic storage and handling
  • Treatment and recovery or disposal
  • Treatment and recovery options include
  • Anaerobic digestion and biogas capture/recovery
  • Stabilisation or composting and use as a soil
  • Incineration and recovery of heat energy
  • Landfill least favoured environmental option

Effluent treatment technology
  • Tertiary treatment of treated sewage effluents
  • Lagooning (prolonged settlement for
  • Filtration rapid gravity, brush filters,
    pebble/edge wire filters, upward flow clarifiers,
    ultrafilitration, reverse osmosis
  • Reed beds
  • Chemical oxidation ozone, UV/peroxide/ozone
  • Absorption activated carbon
  • Disinfection UV, ozone, peracetic acid,
    chlorine dioxide/hypochlorite
  • Tertiary treatment coupled with water recovery is
    becoming more common and will be the normal
    scenario in the next decades.

High Strength Effluent Isolation
  • Gwenda McIntyre, Envirowise

High strength effluent isolation
  • Effluent treatment technologies are most cost
    effective when combined with water and materials
  • Materials recovery from mixed waste streams can
    be technically difficult and more costly than for
    more concentrated process effluents.
  • Process waste streams are generally better
    characterised than mixed site effluents
    treatment processes can be designed to suit the
    more limited range of parameters.
  • However, some process waste streams may have
    characteristics which may limit treatment
  • Pre-treatment may be required e.g. heat exchange
    to reduce temperature, pH adjustment to reduce
    corrosive nature.

High strength effluent isolation
  • To assess site effluent treatment requirements
    need to perform an effluent source and
    composition survey
  • Identify all process effluents produced on the
  • Check records and interview staff to establish
  • Flow rates
  • Composition nature and concentration of
    polluting species
  • If recent data not available, perform a sampling
    and analysis exercise
  • Dont forget site drainage waters!

High strength effluent isolation
  • From the effluent source and composition survey
  • From composition and flow rate data
  • Calculate pollutant loads in kg/day for each
    effluent source
  • Identify the high load and high
    strength/concentration waste streams
  • Evaluate various effluent treatment scenario
  • Consider isolation of all high strength and high
    load waste streams
  • Consider mixing of complementary waste streams
    e.g. to neutralise streams and enhance separation
    of pollutants
  • Compare to costs of options for combining all
    effluent streams before treatment

High strength effluent isolation
  • Options assessment
  • Identify treatment options which reduce overall
    costs and maximise the potential for both water
    and materials recovery
  • If possible
  • Isolate, pre-treat and recover materials from all
    process effluents
  • Discharge treated effluent to sewer or surface
    water if suitable (consent required)

Coffee Break until 3.15pm
  • Investigating effluent sources and identifying
    treatment options.

  • Investigating effluent sources and identifying
    treatment options.
  • You have recently undertaken some sampling of
    your effluent and it contains some interesting
    substances. It does not comply with your agreed
    limits with STW so you need to decide what to do
    about it.
  • In three groups, discuss the information provided
    and consider your options.
  • You will have some time available to talk to the
    site engineer who has information concerning all
    the processes undertaken at the site.
  • Using the information gathered determine how you
    will reduce the concentration of contaminants
    within the effluent to an acceptable level.

Case Studies in Effluent Treatment for Water
  • James Woodcock, NISP

(No Transcript)
Questions and Answers
  • Gwenda McIntyre and Nigel Leehane,
  • Envirowise

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