ENVIROWISE SEVERN TRENT WATER LTD WATER MANAGEMENT PARTNERSHIP

1
ENVIROWISE / SEVERN TRENT WATER LTDWATER
MANAGEMENT PARTNERSHIP

• Workshop 6
• Effluent Treatment
• 28th February 2008

2
Welcome to the Workshop

• Nigel Leehane,
• Envirowise

3
Agenda
4
Workshop 6Effluent Treatment

• Consented discharges
• Water resource protection
• Effluent Treatment

5
Consented Discharges

• Nigel Leehane, Envirowise

6
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
  discharged.
• The sewerage undertaker can refuse consent, or
  grant consent with or without conditions.

7
Consent conditions

• The conditions can include requirements relating
  to any of the following
• periods of discharge
• exclusion from the effluent of all condensing
  water
• elimination or diminution of any specified
  constituent
• 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.

8
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
  implications.
• The Act allows the undertaker to authorise the
  discharge by means of the agreement, rather than
  requiring a separate consent.

9
Water UK

• Water UK is the industry association that
  represents UK statutory water supply and
  wastewater companies at national and European
  level.
• 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

10
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
  causing
• 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
  generally
• Unacceptable storm sewage discharges to
  watercourses
• Installations under the PPC regulations
  special category effluent are subject to dual
  control of the sewerage undertaker and the EA

11
Consents continued

• The consent conditions should also encourage all
  practical means of a reduction at source of the
  volume and polluting characteristics of the
  effluent.
• 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.

12
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

13
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
  issued.

14
Charging

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

15
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.

16
Calculating the Mogden Formula

• S is taken from costs associated with pumping
  sludge to treatment and sludge dewatering and
  treatment
• 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.

17
Charging

• 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
  produces.
• Toxic substances should not be charged for as the
  consent should restrict their discharge to the
  level at which satisfactory treatment can be
  conducted.

18
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
  imposed
• 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

19
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
  installations.
• Trade Effluents (Prescribed Processes and
  Substances) Regs include
• Schedule 1 Red List Substances
• Schedule 2 Prescribed Processes

20
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
  waters

21
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

22
Water Resource Protection

• Nigel Leehane, Envirowise

23
Water resource protection through pollution
prevention

• 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.

24
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

25
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
  water
• Ensure maps and plans are kept up to date

26
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

27
Surfacing

• Design of surfaces, containment and drainage
  facilities for all operational areas should
  consider
• Operational areas should have in place or, if not
  present, should set up an improvement plan to
  install
• 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

28
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
  material
• Have no outlet and drain to a blind collection
  point
• 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

29
Storage areas

• Storage areas for IBCs, drums and bags
• Should be located away from watercourses and
  sensitive boundaries and protected against
  vandalism
• Provide adequate facilities for substances with
  special requirements, e.g. flammable or heat
  sensitive.
• 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

30
Maintenance

• 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

31
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

32
Pollution Prevention Guidance

• The Environment Agency maintains a series of
  Pollution Prevention Guidance Notes (PPGs).
• These apply to all sites not just PPC permitted
  installations
• 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
  /277807/

33
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

34
PPGs by Issue

• PPG 1 - General guide to pollution prevention and
  control
• 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
  sites
• 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

35
PPGs by Issue

• PPG 17 - Dairies and other milk handling
  operators
• PPG 18 - Managing fire water and major spillages
• PPG 19 - Garages and vehicle service centres
• PPG 20 - Dewatering underground ducts and
  chambers
• 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

36
PPG1

• 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

37
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
  contamination.
• 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
  required.
• 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
  spills.

38
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
  pollution
• 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

39
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
  discharge.
• This guidance describes the requirements of
  vehicle washing activities including
  consideration of reducing, reusing, recycling
  wash water and dealing with storage and spills of
  chemicals.
• 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.

40
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.

41
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.

42
Use your EMS for pollution prevention
EMS elements
Water efficiency campaign
Resources, roles responsibilities
Responsibilities for process management, water
management
Competence, training
Spill response training, awareness-raising
Operational controls
Handling procedures, preventative maintenance
planning
Monitoring and measurement
Inspections, monitoring discharges
Internal audit programme
Check adherence to procedures, levels of
competence, etc
43
Effluent Treatment

• Gwenda McIntyre, Envirowise

44
Effluent Treatment Technologies

• Gwenda McIntyre, Envirowise

45
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

46
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)

47
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.

48
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
  photosynthesis
• Creating a barrier to oxygen transfer
• Physically blocking fish gills and preventing
  respiration
• Coating wildlife with oils
• High temperature discharges can also have an
  impact and can therefore be polluting.

49
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.

50
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.
  clays
• 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
  on-line

51
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
  week
• Some down time cleaning, maintenance,
  calibration
• Need a supply of chemicals (acid, alkali and
  oxidant/catalyst)
• Samples are digested thermally or chemically
  (UV/persulphate or ozone) and emitted CO2
  measured by infra-red

52
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
  effluent
• 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

53
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

54
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

55
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
  species
• 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
  floatation
• Filtration e.g. membranes, sand filters, filter
  presses

56
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
  flocculation.
• Clean water from the clarifier is recycled back
  to be used as primary wash-water in many
  applications.

Standard clarifiers
Lamella clarifiers
57
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
blanket
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
58
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

59
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

60
Effluent treatment technologies

• Membrane filtration
• Membrane provides semi-permeable barrier
• Allows selective passage of pollutants through
  membrane
• 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
(archive)
61
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
  preferred
• 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
(archive)
62
Effluent treatment technologies

• Electrolytic separation
• Removal of metals from solution by deposition on
  a conducting surface (electrode)
• High surface area electrode maximises treatment
  rate
• 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

Cathode
_ _ _ _ _ _ _ _ _ _ _ _




-
Feedstream
Treated stream
-
-

Anode
63
Effluent treatment technologies

• Ion exchange
• Exchange of ions with a pre-charged resin/zeolite
  for removal of pollutants and recovery or
  materials
• 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

64
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

65
Effluent treatment technologies

• Adsorption
• Adsorbent substance placed in flow of
  effluent/process water
• Activated carbon, chitin, other adsorbent
• Adsorbent bed taken offline when breakthrough
  approached
• 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
  solutions
• Most effective when other pollutant levels are
  low
• May require pre-treatment to remove suspended
  solids and colloidal matter
• Consider logistics adsorbent material volumes
  may be considerable

66
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
  of
• 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

67
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
  combinations
• UV light/peroxide/ozone combinations

Increasing operations costs
68
Effluent treatment technologies

• Chemical oxidation
• Widely used in removal of trace contaminants from
  groundwaters
• 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
Effluent
Recycle loop
69
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
  removal.

70
Effluent treatment technologies
Typical sewage treatment works technologies
Screening
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
71
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
72
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
  systems
• Microbe populations establish with time, impacted
  by
• Conditions - natural and operational,
• Changes in effluent flow, composition,
  temperature
• 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
  recovery/disposal

73
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
  power
• Anaerobic systems sensitive to certain pollutants
  certain detergents and metals can inhibit
  biotreatment
• Often applied in sequence with aerobic treatment

74
Effluent treatment systems

• Sludge treatment
• Conventional sewage treatment produces sludges
• Primary sludges screens, detritors and primary
  settlement
• 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
  conditioner
• Incineration and recovery of heat energy
• Landfill least favoured environmental option

75
Effluent treatment technology

• Tertiary treatment of treated sewage effluents
• Lagooning (prolonged settlement for
  clarification)
• Filtration rapid gravity, brush filters,
  pebble/edge wire filters, upward flow clarifiers,
  ultrafilitration, reverse osmosis
• Reed beds
• Chemical oxidation ozone, UV/peroxide/ozone
  combinations
• 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.

76
High Strength Effluent Isolation

• Gwenda McIntyre, Envirowise

77
High strength effluent isolation

• Effluent treatment technologies are most cost
  effective when combined with water and materials
  recovery.
• 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
  technologies
• Pre-treatment may be required e.g. heat exchange
  to reduce temperature, pH adjustment to reduce
  corrosive nature.

78
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
  site
• 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!

79
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

80
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)

81
Coffee Break until 3.15pm
82
WORKSHOP 6, EXERCISE

• Investigating effluent sources and identifying
  treatment options.

83
WORKSHOP 6, EXERCISE

• 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.

84
Case Studies in Effluent Treatment for Water
Re-use

• James Woodcock, NISP

85
(No Transcript)
86
Questions and Answers

• Gwenda McIntyre and Nigel Leehane,
• Envirowise

87
Your next steps
88
Dont forget to request Envirowise publications
Use the Publication Request Form or go to
www.envirowise.gov.uk
89
Thank you for your contributions.Now please join
us for lunch!