TECHNICAL BULLETIN. Location of the system. Percolation tests for drainage fields. Cesspool sizing. Suggested Information notices

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1 TECHNICAL BULLETIN Issue 1 Market leaders Whichever product is most suitable for your needs you can be assured of Klargester s quality. Klargester is an accredited company under BS EN ISO quality management system and have been awarded the British Board of Agrément Certification (No. 86/1700) for their market leading treatment plant BioDisc. As long established market leaders in the pollution control industry, Klargester can offer you not only quality products but quality advice. If you have any questions on Klargester s products or on any environmental or legislative queries then please contact our team on the number below. Our UK wide technical team are also available for site visits where necessary. Tel: Fax: BUILDING REGULATIONS H2 MADE EASY BY KLARGESTER: Understanding building regulations and the legislation laid out by the government can often be a potential minefield. Mandatory requirements and the accompanying descriptions may sometimes be confusing and baffling, but this reference tool from Klargester aims to make the process as easy as possible by detailing the relevant Wastewater Treatment Systems & Cesspools section concisely yet effectively. The revised Building Regulations Drainage & Waste Disposal H came into effect on 1st April This Technical Bulletin from Klargester specifically refers to Part H2 and is for use within England and Wales. However, it is important to mention that it is for reference only and it is vital you liaise with your local authority on any points of which you are unsure. For your ease of use, the Bulletin is broken down into clear sections, method by method, so it should be all you need to select a safe and correct installation. Also included are the official terms for each. Key issues that have been affected in H2 include: Location of the system Percolation tests for drainage fields Cesspool sizing Suggested Information notices New guidelines on reed bed systems It is vital to note that any discharge from a wastewater system is likely to require consent from the Environment Agency. Page 1

2 AN INTRODUCTION TO H2: Definitions sometimes prove to be stumbling blocks so in the first instance it is useful to clarify exactly what a wastewater treatment system can be. Unusually, H2 has chosen to define such a system as any one of the following: Septic Tank (complete with Irrigation System) Cesspool Aerobic Treatment System Packaged You will note throughout the document that we have highlighted a number of key points. The H2 regulations refer to a number of generic guidelines that form the basis of the requirements for each of the above treatment methods. (1) Any septic tank and its form of secondary treatment, other wastewater treatment system or cesspool, shall be so sited and constructed that (a) it is not prejudicial to the health of any person; (b) it will not contaminate any watercourse, underground water or water supply (c) there are adequate means of access for emptying & maintenance; and (d) where relevant, it will function to a sufficient standard for the protection of health in the event of a power failure (2) Any septic tank or holding tank which is part of a wastewater treatment system or cesspool shall be (a) of adequate capacity (b) constructed so that is impermeable to liquids etc; and (c) adequately ventilated (3) Where a foul water drainage system from a building discharges to a septic tank, wastewater treatment system or cesspool, a durable notice shall be affixed in a suitable place in the building containing information on any continuing maintenance required to avoid risks to health.! Page 2

3 SEPTIC TANKS: Septic tanks provide suitable conditions for the settlement, storage and partial decomposition of solids which need to be removed at regular intervals. The discharge will require further treatment either from a drainage field/mound or constructed wetland. Siting a Septic Tank: 1.0 Septic Tanks should be sited at least 7m from any habitable part of a building, and preferably down slope 1.1 When the tank is emptied, a tanker is required. The tank should be situated no further than 30m from the tanker access point as long as the tank is installed with an invert depth of no more than 3m. This distance must be reduced if the invert depth is greater than 3m. There should also be a clear access route to the tank Design & Construction: 1.2 For up to 4 users your tank should have a capacity below the level of the inlet of at least 2,720 litres. (2.72m 3 ) and the volume should be increased by 180 litres for each additional user 1.3 Tanks are available in a variety of materials; glass reinforced plastics, polyethylene and steel, all of which should meet the mandates of EN This is a new standard specifying requirements of prefabricated septic tanks serving less than 50 population equivalent 1.4 Tanks made from brickwork or concrete should be 220mm thick, with a mortar cement ratio of 1:3. In-situ concrete should be a minimum of 150mm thick of C/25/P mix 1.5 You should ensure there is no leakage either from or into your tank. It should also be ventilated 1.6 Both the inlet and outlet of your tank should be designed to prevent disturbance of surface scum or settled sludge whilst incorporating two operating chambers. If the width of your tank is less than 1200mm the inlet should be via a dip pipe. Turbulence is another factor and limiting the flow of foul water can reduce this the last 12m of the incoming drain should have a gradient of 1 in 50 or flatter 1.7 Both inlet and outlet pipes need to be easily accessible for sampling, inspection, emptying and cleaning. In addition, suitable cover and frames should be fitted which must be both durable and lockable A Few Points to Remember About Septic Tanks: (a) Septic Tanks do not fully treat sewage, they are simply storage facilities which allow the solids to separate from the liquid effluent. Very little decomposition of the solids takes place (b)they need to be regularly maintained and DO need emptying (c) They must discharge into a correctly designed drainage field or mound. Depending on the daily volume of discharged effluent, there must be both a sufficient area and ground quality to allow the effluent to soak away Page 3

4 DRAINAGE FIELDS AND DRAINAGE MOUNDS: Drainage Fields and Mounds provide secondary treatment of the effluent discharged from a Septic Tank and tertiary treatment for a Packaged Treatment Plant effluent. These drainage fields serve to disperse and treat the effluent. It should be noted that a septic tank must have a drainage field. Assessing Ground Suitability: 2.0 In essence, part H2 now requires percolation tests to be carried out, and if these show the ground conditions to be unsuitable an alternative to a septic tank or drainage field must be sought 2.1 The correct design of these systems is essential, but, as important, is verifying in the first place that the soil and land are suitable to take such a system. This can only be done by carrying out percolation tests in the area of the drainage field at a point 300mm below the anticipated depth of the irrigation drain. The test involves digging at least two test holes and filling them with water. Each test should be carried out at least three times in each hole. The test should not be carried out in severe weather conditions. Only if a satisfactory average result is achieved should an irrigation system be approved. The final design and installation must reflect the percolation test results. Siting a Drainage Field or Mound: 2.2 Your field or mound should be located at least 10m from any watercourse or building 2.5 Your field or mound should not be situated near any other similar system avoiding the ground becoming saturated 2.6 No other underground water supplies or pipes should be situated near or within the disposal area 2.7 No access roads or routes should be situated in the disposal area Design & Construction: 2.8 There should be aerobic contact between the effluent and sub soil i.e. the pipe must be laid well above the water table so that the liquid is able to disperse around the soil or media so that bacteria can treat the contaminants in the discharged effluent 2.9 They should be made of perforated pipe and be laid in trenches not steeper than 1/ Pipes should be laid on a 300mm layer of clean shingle or broken stone graded between 20mm and 50mm 2.11 A layer of geotextile should be used to cover the stone filled trench with the remainder of the trench being filled with soil 2.12 An inspection chamber should be installed between the septic tank and drainage field 2.13 Drainage fields should be set out as a continuous loop fed from the inspection chamber. 2.3 Your field or mound should be at least 50m from any groundwater supply and not in any zone 1 groundwater protection zone 2.4 Your field or mound should be at least 15m from any building Page 4

5 A Few Points to Remember About Drainage Fields: (a) The soil must be suitable. The only way to check this is to do percolation tests over the area of the drainage field, to a depth of 0.5m below the depth where the irrigation drain is to be laid. The percolation tests should be done at the wettest time of the year to get a true result. Many sites become seasonal soakaways and often only work in the summer. It can be the case that in the winter there is free discharge of untreated effluent causing contamination and pollution. You should consult the Environment Agency and local authority to ensure that the site is suitable. Specialist advice is recommended (b) Always use the correct design length/area required. The drainage field should be designed to have at least a 20 year lifespan. If a drainage field or mound fails they are often difficult to recover to operational use and a second area of land may not be available for a new one (c) The total length/area of drain installed should be sufficient both for the volume and the duty required. Due to its improved effluent quality, a packaged treatment plant may have 20% less length than that from a septic tank. (d) It is best to flow into an irrigation system by gravity, but in cases where this is not possible, a pump can be used to transfer the effluent to a different area, or into an artificial mound (e) Once installed, the area around the drainage system must not be impacted by any vehicular traffic. Careful planting must not invade the drains (f) Overflowing soakaways cause environmental problems in the locality. In all cases, your assessment of the soil suitability should be verified with the EA and local authority CESSPOOLS: Siting a Cesspool: 3.0 Your cesspool should be 7m away from any inhabited buildings and the location of the cesspool should be on ground lower than any building 3.1 Your cesspool should be accessible for de-sludging, without taking the contents through a building (which might be hazardous to occupants) and be within 30m of the vehicle access point A Cesspool is a watertight tank, installed underground, for the storage of sewage where no treatment processes are involved. Design & Construction: 3.2 The capacity of the cesspool below the inlet level, for 2 users should be a minimum of 18,000 litres (18m 3 ) and for each additional user this capacity should increase by 6,800 litres (6.8m 3 ) For an average household of 4, this means a minimum volume of litres (31.6m 3 ) A Few Points to Remember About Cesspools: (a) Cesspools may be permitted for installation where no other option is feasible (b) The regulations now call for much larger capacity units (c) No treatment processes occur within the unit, everything that enters must be tankered away (d) Overflowing or leaking cesspools cause environmental problems in the locality (e) One of the key downfalls of cesspools are the financial implications. This is due to high installation costs as well as the regular emptying requirements (f) Due to their large size they also require a large amount of available land 3.3 There should be no opening except for the inlet and to provide access for emptying, cleaning and ventilation 3.4 You should ensure there can be no leakage from your tank or any possibility that the subsoil water can enter the tank, it should also be ventilated 3.5 Covers should be durable and lockable 3.6 Cesspools are available in a variety of materials; glass reinforced plastics, polyethylene and steel all of which materials should meet the requirements of EN Cesspools made from brickwork or concrete should be 220mm thick, with a mortar cement ratio of 1:3. In-situ concrete should be a minimum of 150mm thick of C/25/P mix Page 5

6 PACKAGED TREATMENT WORKS: This term is applied to a range of systems engineered to treat a given hydraulic and organic load using prefabricated components which can be installed with minimal site work. They use a number of processes which are different in detail. Some, such as Klargester s BioDisc, treat the incoming effluent to such a high quality that the final discharge may, with The Environment Agency s permission be allowed to enter directly into a watercourse. Siting A Packaged Treatment Works: 4.0 The discharge point from your treatment plant should be situated at least 10m from a watercourse or building Design & Construction: 4.1 Ensure your packaged treatment works is type-tested in accordance with BS 7781 or another recognised body 4.2 In case of a power failure you need to ensure that your packaged treatment works can still function normally for up to 6 hours thus minimising any danger of leakage or contamination Key Benefits of Packaged Treatment Works & The BioDisc from Klargester: As you can see, the pros and cons of septic tanks, cesspools and packaged treatment plants vary immensely. However, in the long term a Packaged Treatment Works such as Klargester s BioDisc provide a number of real benefits and attributes that should make it your preferred choice when choosing a waste water management system. The following points outline those benefits: (a) Similar in size to a septic tank, the BioDisc provides a compact and efficient complete treatment system (b) The BioDisc actively treats sewage, breaking down solids and pollutants using natural methods before safely discharging treated effluent into the environment (c) The BioDisc has a unique design. It is the only packaged treatment unit to utilise the Rotating Biological Contactor technology which offers a refined treatment process and a superior effluent quality (d) It is supplied with lifting and lowering fixings so it is quick and easy to install on a suitably prepared site (e) With Environmental Agency permission, discharge may be direct to a watercourse avoiding the expense of an irrigation system. The final effluent quality means that where an irrigation system is required,the length may be reduced by 20% (f) The BioDisc is simple to operate. Once switched on, it runs continually using a 60 watt motor, meaning lower running and maintainance costs (g) The biological treatment process is refined by Klargester s unique patented Managed Flow System to ensure optimum performance throughout the day coping with variable incoming flows and strengths (h) The sophisticated internal design with separate compartments means that should power fail, the incoming sewage is managed through a defined flow route displacing only treated effluent thus complying with the requirement to function normally for six hours (i) British Board of Agrément Certification, manufactured in accordance with ISO A Few Points to Remember About Treatment Works: (a) As you can see, the regulations only detail where the discharge for your works should be. They do not provide minimum distances of the works actual location. We recommend you liaise with your local authority on this matter (b) A new industry standard, pr-en , will be published in the near future outlining new requirements for Packaged Treatment Works. This will cover a number of construction criteria as well as requiring a performance test (c) All packaged works require power to operate, when power fails, sewage will continue to enter the works and should be displaced without adversely affecting the discharge quality. Unit designs differ, a unit which manages or controls the flow via a long process flow route will maximise separation or treatment. Under no circumstances should raw sewage be able to overflow out of the outlet Page 6

7 REED BEDS/ CONSTRUCTED WETLANDS: Reed Bed Treatment Systems or other constructed wetland treatment systems can be used to provide secondary treatment of effluent from septic tanks or tertiary treatment from packaged treatment works. The systems provide an extra treatment process to the incoming wastewater as it moves through the gravel bed around rhizomes and roots, removing organic matter, oxidising ammonia, reducing nitrate and removing a little phosphorous. The mechanisms are complex and involve bacterial oxidation, filtration, sedimentation and chemical precipitation.! Reed Beds and Constructed Wetlands are a new addition to New Addition to H2: the building regulations and many incorrectly believe they are the easy and eco-friendly future for wastewater treatment. We have listed some popular misconceptions below. As with all biological treatment systems they have specific sizing requirements. They are however, particularly effective when coupled with a Packaged Treatment Works as they provide an additional polishing stage of treatment. Types of Systems: Horizontal Flow Systems are continuously fed with wastewater from one end and tend to be oxygen-limited and therefore tend not to be able to completely treat concentrated effluents particularly those with high levels of ammonia. Vertical Flow Systems are intermittently fed (pump dosed) with wastewater flooding the surface of the bed followed by a period of rest. Two or more beds, each with a depth of at least 1.2m are usually installed so that they can be used in rotation. Bed rotation however, does require regular attention or additional equipment or valve arrangements. Maintenance requirements are higher than horizontal systems. Klargester are aware of the public s interest and specifiers in Reed Beds and Wetlands and manufacture a range of products that further enhance the service offered by Packaged Treatment plant. The following points outline those benefits of Klargester Reed Beds: (a) A packaged solution complete with all fittings and plants (b) Correctly designed and sized (c) Easy to install as there no difficult holes to prepare, liner to lay or complicated pipe-work to fit (d) Aesthetically pleasing and environmentally friendly with low maintenance (e) The only additional running costs are when a pump is required A Few Points to Remember About Reed Bed Systems: (a) Reed beds and Constructed Wetlands must be sized correctly, in accordance with both the strength and volume of waste water (b) Selection of this method of secondary or tertiary treatment depends upon site availability, aspect and slope, and frequently requires pumping equipment (c) Reed beds should not be constructed in the shade of trees or building as this results in poor or patchy growth (d) Performance tends to be poorer in the winter due to lower temperatures Page 7

8 MARKING: Marking is another part of the new regulations as it provides instant reference to end users as well as maintenance and monitoring teams. The regulations provide example wording for each system. This is to ensure that current and future users are fully aware of all necessary maintenance and operation requirements of their selected system. Manufacturers should provide a notice but the placing of this notice is at the owner s discretion, but owners should remember that they are responsible by law for ensuring that their chosen system doesn t cause pollution, a health hazard or nuisance. YOUR QUICK REFERENCE TABLE: Issue Septic Tank Drainage Field Cesspool Packaged Treatment Plant Reed Beds & Constructed Wetlands Description Settles the solids in the sewage and then releases the effluent to a drainage field where biological breakdown is meant to take place Provide secondary treatment of the effluent discharged from a septic tank and tertiary treatment for a Packaged Treatment Plant effluent Simply stores the effluent until tankered away Takes the effluent and fully treats it through a biological process to enable safe discharge Provide secondary treatment of effluent from Septic Tanks or tertiary treatment from Packaged Treatment Works. The systems provide an extra treatment process to the incoming wastewater as it moves through the gravel bed around rhizomes and roots, removing organic matter, oxidising ammonia, reducing nitrate and removing a little phosphorous H2 Highlights Septic Tanks should be sited at least 7m from any habitable part of a building, and preferably down slope Percolation tests must now be carried out and if these show the ground conditions to be unsuitable an alternative must be found The capacity of the cesspool, below the inlet level, for two users should be a minimum of 18,000 litres (18m 3 ) and for each additional user this capacity should increase by 6,800 litres (6.8m 3 ). For an average household of four, this means a minimum volume of 31.6m 3 In case of power failure you need to ensure that your Packaged Treatment Works can still function normally for up to 6 hours, thus minimising any danger of leakage or contamination Reed Beds and Constructed Wetlands are a new addition to the building regulations Marking The new H2 regulations state that for each treatment method 'A notice should be fixed within the building describing the necessary maintenance' Each treatment method has different wording which is required. Therefore, it is necessary to consult your copy of H2 to ensure you meet the necessary criteria. Responsibility It is the responsibility of the owner or occupier of the building, to ensure that all manditory legislation is adhered to. This can principally be achieved by consulting this bulletin and the official version of H2 H2 CONCLUSION: Hopefully this Technical Bulletin has provided you with a condensed and easier to understand guide to waste water treatment systems without losing any key facts. It is designed to ensure the installation goes as smoothly as possible and that it meets all the necessary requirements with as little confusion as possible. Local authorities and The Environment Agency have powers to ensure that water treatment systems or cesspools are adequately maintained. H2 states that specialist knowledge is advisable in the design and installation of small sewerage treatment works. Klargester s UK wide technical team are able to provide specialist knowledge and guidance. Ultimately these new regulations must be adhered to otherwise it could result in prosecution or costly changes. If you are in any doubt we strongly recommend you consult your local building authorities. The EA Pollution Guideline PPG4 and DETR circular 03/99 also provide guidance in respect of equipment selection and planning requirements. Contact Details: For further information and enquiries on the installation of Klargester s BioDisc please call the sales team on Page 8