Rural wastewater treatment in the United Kingdom

1. Rural wastewater treatment in the United Kingdom Dave Diston, Huw Taylor School of Environment and Technology, University of Brighton

2. Characteristics of UK aquatic pollution • Point/diffuse source contribution of P to surface waters is estimated to be 50:50 – N is biased towards diffuse • Point source contribution judged to be of greater importance to riverine eutrophication (SRP; PO4) • Government action (no specific rural sewage treatment plan): • Adoption of numerous EU Directives (UWWTD, WFD etc); • Agri-environmental schemes. http://www.defra.gov.uk/erdp/schemes/es/default.htm

3. UK water industry – Key facts - Transition from public to private (1989) - Drivers: • Removal from government financial regulations. Newly created private companies were granted increased borrowing powers free from Treasury constraints; • New companies were floated on the stock market, upon which previous accrued debts were written off, making shares more attractive; • The companies were allowed to increase water and waste processing prices (subject to regulation). Table 1: Price changes in the post-privatisation period (Ofwat) Profit production was now of major importnace

4. Companies involved in water service industry Water and sewage Water only 98% of UK households are connected to the mains sewerage network, owned and operated by 11 private regional water and sewerage companies London Brighton

5. Have goals of privatisation been achieved? Table 2: Average annual capital investment Privatisation

6. Current practices and methods available for the treatment of non-mains connected rural households (2%)in the UK (i) • Cesspool (storage only, little treatment) Filter Gravel Pipe delivering sewage from single property (>15m) After construction, an airtight lid must be placed over cesspool Capacity = 18 – 50 m3 Pebbles and rocks PROS = Cheaply & quickly built; CONS = No treatment, frequent emptying (££), access required

7. Current practices and methods available for the treatment of non-mains connected rural households in the UK (ii) • Septic tank (primary sedimentation and some biological treatment) Up to 70% BOD removal Design details can be found in British Standard BS 6297:1983 PROS = Decent treatment (30/20), de-sludging ~ 1 year, easily maintained ; CONS = Potential for bio-damage, backing up common

8. Design and capacities vary greatly depending on population to be served Two septic tanks in series for populations up to 30 persons (BS 6297:1983)

9. Current practices and methods available for the treatment of non-mains connected rural households in the UK (iii) • Packaged plants (sedimentation and biological treatment) Various configurations e.g. Activated sludge/ biofiltration etc. PROS = High level of treatment; CONS = Expensive (6 person = £2,000+)

10. Other options: Small STW (same in principle to large STW – albeit on a smaller scale). Tertiary treatment: Grass plots; Upward flow clarifiers; Effluent lagoons; Reed bed systems Current practices and methods available for the treatment of non-mains connected rural households in the UK (iv) Technical drawings of all systems are available upon request

11. Extent of methods (i) Table 3: Drainage attributes in UK households by construction date Inc via private sewer Proportions have remained relatively stable

12. Extent of methods by region (ii) Table 4: Sewerage in England and Wales 1 Figures are estimates and apply to septic tanks only 2 Figures are estimates and apply to septic tanks and package sewage treatment works No clear spatial patterns

13. Different experience of rural sewage processes to other Lakepromo partners – most rural households are connected to the mains sewerage network  sewage is processed in central STW Many rural properties are connected via Private Sewer Networks Current practices and methods available for the treatment of mains connected rural wastewater in the UK (i)

14. Current practices and methods available for the treatment of mains connected rural wastewater in the UK (ii) • Private Sewers • There are approximately 9,450,000 properties served by private sewers in the UK of which it is estimated 7,097,500 (75%) are located in rural areas • Recent data indicated there were a total of 282,000 internal and external-flooding incidents per annum associated with all private sewers. However, Local Authorities only recorded 120,000 sewer related flooding incidents, whilst Ofwat only recorded 5,700 internal flooding incidents. Therefore, it is likely many sewer faults are not reported, limiting the chance of exercising damage mitigation strategies. Table 5: Condition of private sewers Note: Internal Condition Grade (ICG) 1: Acceptable condition ICG2: Short-term risk of collapse is minimal ICG3: Collapse unlikely in near future, but likely to deteriorate ICG4: Collapse likely in foreseeable future ICG5: Collapse imminent/collapsed

15. Current practices and methods available for the treatment of mains connected rural wastewater in the UK (iii) Table 6: Reasons for private sewer faults Total faults = 261,000

16. Other areas included in the UK Rural Sewage Treatment Information Package • History of UK sewage treatment • Administrative structure and legislation • Planning and implementation procedures • Methodology for selection of appropriate system • National special expertise (reed bed systems) • Investigation into nutrient stripping within the UK

17. Thank you for your attention! Questions after part II