Liquid Waste Disposal

There are only two legal methods for liquid waste disposal:

• The business can use a recognised waste consignment (“haulaway”) service
• Obtain a ‘Consent to Discharge Trade Effluent’ from the local Water Services Companies so that waste can be discharged to the drains.

This Code of practice recommends a choice of methods for waste photoprocessing liquids disposal depending on the system in operation.

Trade Effluent

Trade effluent is:

• Liquid.
• Produced in the course of any trade or industry on trade premises.
• Not domestic sewage or other domestic liquid waste.

Trade Effluent is defined fully in the 1991 Water Industry Act. It is an offence to discharge it without the formal consent of the Water Services Companies or when in breach of any condition of such a consent.

The Urban Wastewater Treatment Regulations 1994 require Water Services Companies to exercise their powers under the Water Industry Act 1991 and write conditions into trade effluent consents and agreements to prevent trade effluents (either alone or in combination with other waste) causing damage or harm to:

• the sewerage system
• the sewage treatment works
• employees and the general public
• the environment in general

The Sewerage System

Controls on trade effluents are necessary to prevent them causing:

• Corrosion of the material of construction of the sewer, especially concrete pipes and mortar joints.
• Blockage or hydraulic overloading of sewers leading to foul flooding of property or pollution of watercourses via network overflows.
• The formation of explosive, flammable or poisonous gases in the sewerage system which may be prejudicial to the health of personnel maintaining the sewerage system or the cause of danger or a nuisance to adjoining properties.
• Unacceptable discharges in times of rainfall from storm overflows on the sewerage system.

The Sewage Treatment Works

The works must be protected to ensure that:

• The available plant can treat the sewage arriving at a works effectively and economically.
• Damage does not occur to the structure of the works or to mechanical, electrical and instrumentation equipment
• Personnel employed in the operation of the treatment works are not harmed.
• Biological treatment processes are not poisoned or inhibited by toxic substances.
• Sewage treatment works effluent does not adversely affect the environment or prevent receiving water from complying with European Union Directives.
• Sewage sludge can be re-cycled or disposed of safely in another environmentally acceptable manner.

Water Services Companies regulate discharges of trade effluent to the public sewer. They are themselves subject to regulation (and legal action) by the Environment Agency in respect of effluents and sludge’s produced in the sewage purification process.

Example of Substances Requiring Control

Many chemicals used in photography will be completely degraded into harmless natural products in the sewage purification process. Their concentrations need not usually be limited as long as the local sewerage system and associated sewage treatment works provide adequate dilution. Advice will be given by the relevant Water Services Companies on request.

However, certain constituents of photographic effluent will be subject to specific controls, for example:

• acidity (corrosion)
• ammonia (toxicity/nuisance in sewer and toxicity/oxygen demand in receiving water)
• silver (possible toxicity)
• sulphur (sulphates and sulphides; corrosion/nuisance)
• high oxygen demand (effect in sewers and overloading of treatment process)

This Code of Practice contains examples of working limits set by the Water Services Companies and which should be achievable by photo-processor operators.

Working Limits for Effluent Composition

Trade Effluent Consents issued by Water Services Companies will usually contain the following requirements:

1. No trade effluent shall be discharged having a pH <6.0 or >10.0
   
   
2. Trade effluent shall not contain:

• Sulphides, hydrosulphides, polysulphides and substances producing hydrogen sulphide on acidification in excess of 1.0 mg/l.
• Sulphates as SO4 in excess of 1000 mg/l.
• Toxic metals in excess of 5 mg/l either individually or in total, e.g antimony, arsenic, beryllium, chromium, copper, lead, nickel, selenium, tin, vanadium and zinc.
• Cyanides and cyanogen compounds, which produce hydrogen cyanide on acidification in excess of 1.0 mg/l.
• Total suspended solids at pH 7.0 and dried at 110oC in excess of 400 mg/l.
• Settled chemical oxygen demand in excess of 1000 mg/l.
• Silver in excess of 5 mg/l.
• Ammonia in excess of 250 mg/l

It is important to understand that limit values may vary from place to place depending upon the size of the sewage treatment works, dilution in the receiving watercourse and other industrial discharges in the catchment area.

Consents to Discharge and Charges for Trade Effluent

Consents are obtained from the local WSC and specify the composition and quantity of effluent that can be discharged to the sewer system from a particular site.  The local WSC can provide full details upon request.  Minilab operators (see section 6.1) will not normally require WSC Consents if they use waste consignment as recommended.

IT IS VITALLY IMPORTANT THAT ALL DISCHARGES ARE MADE TO A FOUL SEWER AND THAT NO DISCHARGES ARE ALLOWED TO ANY RAINWATER, OR OTHER SURFACE OR GROUNDWATER, DRAIN.

The photo-processing operator should have a floor plan indicating areas of chemical storage, processing equipment and identifying all drains suitably colour-coded (i.e. foul drains red and surface drains blue).

Subject to meeting the following requirements, the photo-laboratory can apply to be put onto the fixed charging system:

1. Proof of waste consignment and/or outline of silver recovery system
2. Storage and spillage policy and
3. Water supply and drainage plan.

Trade Effluent Charges - “Mogden” Formula

All Water Services Companies use a “Mogden”-type formula to charge for trade effluents.  The basic “Mogden” formula is:

Where:-

C = total charge per cubic metre of trade effluent

R = reception and conveyance charge

V  = volumetric and primary treatment cost

Ot  = the COD of the trade effluent

Os = the average COD of settled sewage for the region

B = biological oxidation cost

St = the suspended solids in the trade effluent

Ss = the average suspended solids in crude sewage for the region

S = treatment and disposal costs of primary sludge

The purpose of the formula is to match (as closely as possible) the trade effluent charge to the cost of providing the services of reception and conveyance of the trade effluent and its subsequent biological oxidation and sludge treatment and disposal.

The four unit costs (R, V, B and S) together with the COD and solids content of sewage are fixed annually in advance by the Water Services Companies.

COPPICE recommends that the COD and suspendid solids content of the trade effluent are also fixed for general photo-processing laboratories at 350 ppm and 35 ppm respectively. For other than general photo-processing labs the charge will depend on the actual wastes. Any additional processes may change the COD and Ss values and hence the charges.

The only remaining variable in the formula is the volume of trade effluent actually discharged that should be determined from the water meter for the incoming supply or the sub-meter to the process.

The use of standard strength will ensure consistency within the area covered by each of the Water Services Companies. There will still be regional differences in charging owing to different tariffs between the Water Services Companies.

IMPORTANT NOTE: An extra charge may be made depending on local circumstances.

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Minimising the Impact and Cost of Trade Effluent

There are cost effective on-site treatments for photoprocessing wastes to reduce the amount of silver in effluent at photoprocessing premises although they are unlikely to be economical for Minilab operators.  Together with water recycling and chemical management systems, operators can reduce their overall cost of effluent.

A. On-Site Silver Recovery

Several systems are available to achieve the limits required.

The photo-laboratory must be able to demonstrate how their operating system will be able to comply with the silver limit under normal operating conditions.  It is recommended that a flow diagram is drawn up showing the equipment involved and the expected silver levels at each output stage.

B. Use of Water Recycling Equipment

There are several water recycling systems available which generally offer a large reduction in water usage (often in excess of 90%), as well as savings on water heating costs and reduction of emergency water storage.  From a water and energy conservation viewpoint, their use is to be supported.  However, it must be realised that the trade effluent concentration will be radically altered by the reduction in wash water and dilution. In other words, the waste will be more concentrated, and possibly more hazardous, to handle and transport. Consequently it may be necessary to have much of the trade effluent hauled away in order to meet discharge consent levels.  Anyone considering installation of a water-recycling unit is advised to discuss the matter with their local Water Services Companies to ensure that all parties' interests are maintained to achieve the best possible result.

Waste Consignment

Under the Hazardous Waste Regulations introduced in July 2005, if you produce and/or store waste on site you need to register your site with the Environmental Agency as a Hazardous Waste Producer. You will be issued with a Registration Number without which you will be unable to consign hazardous waste from your site. Under these regulations most photoprocessing wastes are classified as hazardous. Although if "continuous" on-line treatment is used to process the waste, this aspect of waste may be exempt from the calculation (Consult your waste management contractor or seek confirmation from the Environment Agency).

For waste consignment, the Minilab or photo-laboratory must be able to provide reasonable proof that all silver-bearing effluent is gathered together (in suitable containers) for collection by a registered waste carrier. 

Records of volumes collected, nature, origin, destination, mode of transport European Waste Catalogue number, UN number and treatment method transfer notes and billing by the final waste Treatment Company must be retained for a period of at least three years.

All other requirements of the 'Duty of Care' legislation and Hazardous Waste Regulations must be satisfied.

The photochemical suppliers will be available to advise on using haulaway services.

The waste contractor providing the consignment service should also be able and willing to provide any assistance required to ensure the organisation satisfies the legal requirements.

IMPORTANT NOTE: The originator (producer) of the waste is responsible for it’s safe and lawful disposal.

Many non-silver-bearing wastes produced in the photo-processing industry must also be subject to waste consignment for disposal rather than be discharged as effluent.

If in doubt, seek advice.

Hazardous Waste

There is much confusion in industry generally about the disposal options for waste classified as Hazardous (previously known as Special).

Classification as Hazardous does not necessarily mean that the waste cannot be discharged to sewer as Trade Effluent.

In many cases the disposal route with least environmental impact is via the local sewage treatment works, which are designed to treat a wide range of materials before they are passed into the natural environment.

Your Water Services Companies will be able to advise on what is an acceptable discharge to their sewer (this can vary from company to company and on location) and what is not.

Further information on the Hazardous Waste Regulations is available from this Website: www.defra.gov.uk