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Mogden Formula

Water Companies use the Mogden formula to calculate
the costs of discharge to the public sewer.

Chemsol work closely with you to reduce this cost
significantly, even to as little as £ zero.

Visit our full website for more detail – or get in touch

The Mogden Formula is Stated as: C = R + V + Vb + B x Ot/Os + S x St/Ss


C = Total charge rate for disposal (pence/cubic metre)

R = Unit cost for conveyance (pence/cubic metre)

V = Unit cost for volumetric treatment (pence/cubic metre)

Vb = Additional volume charge if there is no biological treatment

B = Unit cost for biological treatment (pence/cubic metre)

Ot = COD of trade effluent (mg/l); Os = COD settled sewage (mg/l)

S = Unit cost for sludge disposal (pence/cubic metre)

St = Solids value trade effluent (mg/l); Ss = Solids value* settled sewage (mg/l)

Understanding the Mogden Formula

Wastewater costs vary depending on the receiving company’s charge factors and :

1) Volume flow (amount per day/week/month etc)

2) COD (chemical oxygen demand)

3) Suspended Solids

In other words, reduction in any or all of the above three variables leads to reduced charges – And more control of site costs given that the Water Companies Generate Revenue by Accepting and Treating Wastewater.

Now it can be seen how the quarterly or annual bill is calculated. With the help of the Mogden Formula calculator this cost can be predicted and show how on-site treatment can reduce this cost.

Contact us and ask for a free copy of our Mogden Formula Calculator

The Mogden Formula calculates the charges water companies apply to industry for the conveyance and treatment of effluents discharged to the public wastewater network. These charges are based on the limits agreed with the company in its Trade Effluent Consent.

The tool uses water companies’ standard tariffs, but if you are a large water user there is an ‘other tariffs’ option which allows you to enter industrial tariffs.

The Mogden Formula Calculator also allows the user to investigate the impact of modifying specific aspects of the effluent on the cost to discharge. For example, the flow, COD and SS can all be modified independently to investigate whether a preliminary treatment system may be a cost-effective option to consider.

The intelligent use of Chemical and Biological techniques have been perfected with years of experience, this with the ability to provide a combined engineering, installation and maintenance programme, means Chemsol is the one stop solution for the success of your treatment plant and your business.

Treatment of waste water is high on the agenda for businesses in Wales as Dwr Cymru has strong policy on effective treatments and charges in relation to the effectiveness of treatments. In essence it can be very cost effective for a business to clean up its own waste water. Chemsol proven in that field and has made hugely significant saving for many of it’s clients.

Wales have one of the longest coastlines so having high quality coastal water quality is especially important for the Welsh tourism industry which employs an average of 100,000 people and makes a significant contribution to the Welsh economy. Since 1995 Dwr Cymru have invested over £1 billion on upgrading or building new wastewater treatment works right across our region which has helped Wales secure European blue flag awards.

Sewer pipes – whose responsibility?
Welsh Water is responsible for sewerage pipes from the point at which they join the public sewerage system. Many properties drain through a private sewer in order to reach this public sewerage system.

Historically, private sewers are, in the main, sewers that have not been built to adoptable standards and responsibility for their maintenance and repair lies with the owners of the properties connected to them. In recent years, a number of problems concerning private sewers have arisen; not least the fact that many businesses and households aren’t aware that their property is served by a private sewer until there is a problem with it and it needs to be repaired. When this situation arises, it can often cause significant concern to those affected as there are often high costs involved in carrying out repairs.

The Welsh Assembly Government has been working with the Department for Environment, Food & Rural Affairs (Defra) and other key stakeholder to try and find a means of resolving the situation. To prevent the situation from being further exacerbated a protocol was agreed in 2002 that encourages house-builders to construct all new sewers to adoptable standards. With regard to a longer-term solution a decision was made “in principle” by the Welsh Assembly Government in February 2007 that ownership of private sewers and lateral drains should be transferred to sewerage companies.