The following list of frequently asked questions and answers was compiled by our technical team and covers most of the queries we think you might have regarding sewage treatment plants.

If there is anything else you wish to know, please call our friendly customer service team on 06 89 54 91 38  (English)

What is the difference between a septic tank and a sewage treatment plant?

A septic tank receives untreated wastewater from a property and allows the heavier solids to settle at the bottom whilst the effluent rises to the top. Self forming bacteria help the system digest the solids or sludge and the remaining liquids flow out of the tank into a drainage field. The effluent from a septic tank still contains about 70% of the polluted matter in the sewage, and further treatment is necessary. Alternatively, a sewage treatment plant gives aerobic digestion of the wastewater contaminants, and treats to a much higher standard than a septic tank. Treatment plant effluent has the appearance of clear water and can be discharged into a water course or ditch (with Environment Agency approval) or to a conventional soakaway.

Treatment plants also vary, some have internal moving parts and others do not. The WPL Diamond plant has no internal moving parts and as a result requires minimal maintenance.

Do plants have to comply with EN/CE Regulations?

Yes, all small treatment plants up to 50 persons must, by law, be fully type tested and certified with the CE Mark accordance with EN12566-3. All manufacturers should be able to produce their certificate on request. It is also important it complies with Environment Agency consent standards and is designed in accordance with British Water Codes of Practice Flows and Loads, to ensure correct sizing of all tanks. The full Diamond DMS and DMC Domestic Sewage Treatment Plants Range is fully type tested and certified in accordance with all these regulations.

WPL Diamond

Is approval required to install a Sewage Treatment plant? For help with French Regulations call 06 89 54 91 38  (English)

All sewage treatment plants need to be registered with the Environment Agency (EA) as they may require an environmental permit, or they will need to register for an exemption from this permit if they meet certain requirements. The environmental permit was formerly referred to as a ‘consent to discharge’ as it is an application to discharge treated water to surface water e.g. a stream or estuary, or to ground water via an infiltration system.

EPP2 (Environmental Permitting Programme): If the sewage treatment plant is eligible (certificated and CE Marked EN12566-3), it can be registered for a free exemption from the need to have a permit under the Environmental Permitting (England and Wales) Regulations 2010. There are certain conditions associated with registering for this exemption concerning the design, installation and maintenance of the sewage treatment plant. If the treated water is being discharged from an approved domestic sewage treatment plant to a soakaway, the plant will usually be eligible to register for an exemption. All of the plants within the WPL Domestic Diamond sewage treatment range will be eligible to apply for an exemption to the permit. The EA will inform applicants if they are not eligible for a registration and therefore that they require a permit.

Do sewage treatment plants or septic tanks smell?

If a sewage treatment plant has a holding area or primary settlement tank then smells may occur, as is often the case with septic tanks. However, plants which use a continuous aeration process with no primary settlement and no septicity, such as the WPL Diamond Plant, should not emit odours. Therefore the treatment process for the Diamond plant is odour free.

What if a property is on a slope and cannot use gravity to discharge the water coming out of the plant?

You need to recommend a plant which has a pump that can cope with discharging up an incline. It is important to ask this question before placing an order as some plants, such as the WPL Diamond, have a separate model which has an integral pump chamber as part of the plant.

WPL manufacture a Diamond DMS-IPC range of Diamond Sewage Treatment Plants which has all the existing features of the Diamond plant but with an extra Integral Pump Chamber (IPC). The IPC is designed to pump treated water from the plant to a water course or soakaway, in area’s that may have an incline, a high water table or a long distance to the soakaway.

What if there is a high water table?

The most suitable systems again would be a plant with an integral pump such as the DMS-IPC. This means the plant can be installed above the water table to avoid problems such as overflowing or backfilling with flood water.

How far from the building should the Diamond plant be sited? For help with French Regulations call 06 89 54 91 38  (English)

Environment Agency Building Regulations state that all sewage treatment plants should be sited 7m-10m from any inhabited part of the property. The building control officer for the site will make the final decision on exactly how far the plant should be sited.

How long will I have to wait for delivery?

Some merchants may carry stock, but for example WPL process their orders immediately and can deliver most standard domestic plants to site between 5 and 7 working days.

How are deliveries arranged and what size lorry will be delivering the tank? For help call 06 89 54 91 38  (English)

If there are any site restrictions these must be notified to the merchant when ordering. For example, WPL’s plants are delivered direct to site, or to the Builders Merchant yard if required and transport can accommodate various site situations. A range of vehicles and off loading options are available if requested.

Can the invert level be altered to suit site conditions?

Yes, a range of turret extensions are available to suit site invert levels. On smaller tanks, whole body extensions are available for especially deep inverts. Always specify the required invert when ordering a system.

The WPL Diamond range offers one of the widest choices for invert extensions, giving it complete flexibility for different site conditions and installation requirements. Invert extensions are available for the full Diamond and Diamond IPC ranges.

How often do sewage treatment plants need to be emptied or de-sludged?

It depends on how the treatment plant works, and how much it is used. Some plants have to be emptied every six months or annually, and some like the WPL Diamond can have extended emptying periods up to 3 years, this saves the customer money on tankering and is often a high priority when recommending a plant.

What about service and maintenance?

The Environment Agency recommends that all treatment plants and septic tanks are regularly maintained to avoid polluting the environment. Most reputable manufactures will offer or be able to recommend British Water accredited service engineers to carry out this maintenance and they will also offer comprehensive warranties.

For help with French Regulations call 06 89 54 91 38  (English)

This list of frequently asked questions was compiled to cover most of the commonly asked questions  relating to the WPL Diamond Sewage Treatment plant.  The WPL sales team will be pleased to help with any other information required on all products and we have a team of representatives who are available to attend site visits to give customers specific information relevant to their particular site and their individual needs.  

Contact us with any Questions and Enquiries on the Sewage Treatment Plants