Reference note: Charges For Trade Effluent
Last updated: (February 2005)
Introduction
All industrial waste waters (trade effluents) are subject to a discharge consent system under either the Water Resources Act 1991 or the Water Industry Act 1991. This briefing sheet provides an overview of the charging system as currently employed in England and Wales.
Information
Three categories of waste waters are can be discharged from commercial premises:
Domestic Sewage - effluent from staff toilets, wash hand basins, showers, and kitchen areas. This is also sometimes known as foul drainage and will usually be kept separate from the trade effluent whilst on the company site, although it is mixed once it reaches the main sewerage system. The charge for this is usually included as part of a water bill from the local water company.
Trade Effluent - effluent from all processes on the site, including all rinse water, washing water and any other discharge related to the process (even if it is clean water). The local water company charge for this if it goes to sewer according to a standard formula (see below). Occasionally, effluent is discharged directly into a river or other water course: in this instance, the Environment Agency make a charge.
Trade effluent is legally defined as "any liquid, either with or without suspended particles, which is wholly or partly produced in the course of any trade or industry carried on at trade premises". It does not include domestic sewage.
Rainwater - rainwater from roofs, carparks and other outside areas discharges into a surface drainage system. This is separate from the foul drainage system and is regulated by the Environment Agency rather than the water company. Rainwater is either channelled to surface drains located in roads adjacent to the property or is sometimes discharged directly to a river or stream. There is not normally a charge for discharge of rainwater, although companies do have a duty to ensure it is not contaminated by oils or any other substance.
Consent to discharge
The Water Industry Act gives companies the right to discharge to a public sewer but only with the prior consent or agreement of the water company.
Water companies maintain the sewerage system, provide treatment for the waste, and dispose of the final treated effluent. To allow them to do this effectively, they can impose special restrictions on an effluent before allowing the discharge.
These restrictions depend upon the type of treatment provided by the water company, the size of connecting sewers and the capacity of the waste water treatment works (WWTW). They can also include:
- the nature or composition of the effluent
- the maximum daily volume allowed
- the maximum rate of flow
- the sewer into which the effluent is discharged.
A number of other factors may also be included in a consent to discharge, eg the temperature or pH of the effluent. Certain substances are prohibited from being disposed of in this way.
In addition to the type and quality of the effluent, the Water Industry Act also gives the water companies the right to charge for carrying, treating and disposing of the waste.
Discharge to sewer
The charge levied by the water company for discharging trade effluent is calculated using a formula which takes account of the volume and "strength" of the waste and the type of treatment given at the WWTW. The formula is commonly known as the "Mogden formula" or "modified Mogden formula" (after the name of the sewage treatment works where it was first used).
Most water companies use a version of the formula developed through liaison between the CBI and the water authorities in 1974. A common form is shown below, but the actual formula used by individual water companies can vary, so it is always best to check with the local company.
| C=R+[V+Bu] OR VM OR M+B |
Ot+S |
St |
|
Os |
Ss |
where:
| C |
= Total charge in pence per cubic metre of trade effluent |
| R |
= Reception and conveyance cost per cubic metre of sewage |
| V |
= Volumetric and primary treatment cost per cubic metre of sewage treated |
| Bu |
= Additional cost per cubic metre where there is biological treatment |
| VM |
= Treatment and disposal charge for sea outfalls |
| M |
= Cost, per m3 of sewage, of providing and operating effective marine outfalls |
| BS |
= Biological oxidation cost per cubic metre of settled sewage (including the cost of secondary sludge disposal) |
| Ot |
= The Chemical Oxygen Demand (COD) in mg/l of the trade effluent after settlement for a specified period (usually one hour) |
| Os |
= The COD (mg/l) of average strength settled sewage |
| St |
= The total weight of suspended solids (mg/l) of the trade effluent |
| Ss |
= The total weight of suspended solids (mg/l) of average strength crude sewage. |
The R,V,B and S factors in the above equation are the regional average unit costs of reception, transport, treatment and disposal of sewage.
The B and S factors being multiplied by a factor which relates the strength and solids content of the trade waste to that of domestic sewage.
Effluent discharges to rivers, or other water courses
The Environment Agency has introduced a system of charges for the recovery of its costs from companies who discharge effluent in this manner. Charges are calculated according to the composition of the effluent, the quantity discharged and the quality of the receiving water. A banding system is used to classify types of effluent. The bands progress from A to G, where A is the most polluting.
The national formula for calculating charges is:
| Charge = R (V ? C ? RW)
where:
R=annual charge financial factor (?477 for 1999/2000)
V=banded weighting factor based on consented discharge volume
C=banded weighting factor based on consented discharge content
RW=banded weighting factor based on category of receiving water. |
Weighting Factors
| Band |
Content of discharge |
Factor (C) |
| A |
Where the consent conditions contain numeric conditions for any of the following; (excluding any condition for total oil and grease)
- pesticides, herbicides, fungicides
- polyhalogenated biphenyls
- polynuclear aromatic hydrocarbons; aliphatic, aromatic, heterocyclic and halogenated hydrocarbons
- alcohols (except methanol, ethanol, butanol, propanol and glycols)
- aromatic nitrogen compounds
- phenolic compounds (except total and monohydric phenols)
- esters; ethers; ketones; aldehydes (except formaldehyde)
- viruses; effluents where consent requires toxicity tests (other than rapid bacterial toxicity tests)
|
14 |
| B |
Except where the consent falls in Band A or authorisation falls in a Band A substance -
Where the consent conditions contain numeric conditions for any of the following:
- metals, metalloids
- cyanides; sulphides
- total and monohydric phenolic compounds
- methanol, ethanol, butanol, propanol; glycols
- carboxylic acids
- organic nitrogen compounds (except those in Band A, urea and quaternary ammonium salts)
- bacteria
- effluent where consent requires rapid bacterial toxicity tests
|
5 |
| C |
Except where the consent falls into A or B
- sewage and organic trade effluent with numeric consent conditions (except those specified in Bands E or G)
- all discharges of trade effluent of an organic nature with numeric conditions other than included in Band E,F,G and H.
|
3 |
| D |
Except where consent falls into A,B,or C
- sewage with no numeric conditions; trade effluent not specified in E
- all other discharges of trade effluent other than those specified in bands E, F, G and H
|
2 |
| E |
Except where consent falls into A,B,C, or D
- site drainage from trade premises
- storm and emergency discharges at treatment works, pumping stations and from drainage systems
- all trade effluents of direct cooling water other than those specified in Band G
- trade effluent from prevention of interference with mining, etc, other than those specified in band F
|
1 |
| F |
- surface water (not containing trade effluent)
- trade effluent from prevention of interference with mining, etc, for which only conditions are volume, suspended solids, iron, pH and chloride
- trade effluent where the consent permits the discharge of water abstracted from the controlled water after use in a trade, subject to limits only in the increase of concentration of biological oxygen demand, suspended solids, and ammonia
- any effluent not identified elsewhere
|
0.5 |
| G |
- cooling water where only conditions are volume, temperature, pH, chlorine
- trade effluent where the consent permits the discharge of water after use for cultivation of plants
|
0.3 |
| H |
Any effluent or substance with no numeric conditions other than volume discharged,
- a maximum daily volume of 5m3 or less per day
- a discharge on not more than 6 days per year or any such equivalent
- a discharge only at specific periods of the year
|
1.5 |
| Volume of discharge (m3/day) |
Factor (V) |
Volume of discharge (m3/day) |
Factor (V) |
| 0 – 5 |
0.3 |
> 1,000 – 10,000 |
3.0 |
| > 5 – 20 |
0.5 |
> 10,000 – 50,000 |
5.0 |
| > 20 – 100 |
1.0 |
> 50,000 – 150,000 |
9.0 |
| > 100 – 1,000 |
2.0 |
> 150,000 |
14.0 |
| Type of receiving water |
Factor (RW) |
| Estuary |
1.5 |
| Surface |
1.0 |
| Coastal |
0.8 |
| Ground |
0.5 |
In addition to this charge, companies are required to pay a discharge application fee of ?617 for most new and revised consents (?88 for certain lesser categories).
Relevant legislation
Water Industry Act 1991
Water Resources Act 1991
Environment Act 1995
The future
With the recent review of the water industry, the majority of water companies will reduce effluent charges with effect on the 6th April 2000. However, it should also be noted that if you are in an area currently receiving limited treatment, should new WWTW be planned this will increase the overall cost of effluent treatment.