WPL offers answers to sewage treatment FAQ's

Published:  21 September, 2010

Building projects in rural locations can often involve off-mains drainage and unless you regularly deal with sewage treatment it can be a difficult to know where to begin when recommending the ideal solution.

The consequences of installing a system which is not suitable or does not comply with current legislation can include the risk of polluting the local environment, combined with the inconvenience and expense to builders and homeowners to rectify any problems. Often failing plants are specified incorrectly from the outset or are not properly type tested under BS EN 12566-3 and CE marked.

WPL Environmental Wastewater Solutions is an experienced manufacturer of wastewater treatment plants which includes their Diamond domestic range and HiPAF commercial range.

Their technical sales team based at their head office in Hampshire, has compiled a useful list of FAQ's to help Merchants when recommending the right type of plant to their customers. WPL also offers technical advice and site visits through their national network of area representatives to support merchants, but many questions can often easily be answered in the branch therefore speeding up the transaction.

Listed below are the most frequent questions asked and the relevant answers.

The enquiries vary from general questions about the types of systems available, installation information, service and maintenance enquiries and queries regarding Environment Agency consents and regulations.

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. For customers requiring minimal maintenance plants, this is also a consideration.

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, for example WPL has theirs available on their website. 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.

Is approval required to install a Sewage Treatment plant?

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 will 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, 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.

What if there is a high water table?

The most suitable systems again would be a plant with an integral pump. 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?

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?

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.

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.

Can customers purchase a treatment plant direct as well as from Builders Merchants?

WPL products are only available through local builder's merchants and are supplied nationwide, delivered to site. Merchants often have promotions or special offers allowing customers to find the most competitive price. Other manufactures may sell direct.

This list of enquiries was compiled to cover most of the FAQ's relating to the WPL Diamond Sewage Treatment plant, although the WPL sales team will be pleased to help with any other information required on all products. WPL's sales team consists of sales executives based at the office, and the sales representatives who are located nationwide. The WPL sales reps are available to attend site visits to give customers information relevant to their particular site and their individual needs.

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