Suchergebnisse

ABSTRACTThe design of septic tanks, constructed wetlands, waste‐stabilisation ponds and rock filters is detailed, and their applicability in the UK is discussed. Septic tanks are a suitable primary treatment system for villages with a population of less than 500. Constructed wetlands, which are secondary or tertiary treatment units, have the disadvantage that their plants do not play any significant role in their performance, except for nitrogen removal. Secondary facultative waste‐stabilisation ponds, with pre‐treatment in septic tanks and post‐treatment in rock filters, provide primary, secondary and tertiary treatment and can produce high‐quality effluents. The costs of these processes for small rural communities in the UK are compared.

ABSTRACTThree pilot‐scale primary‐facultative waste stabilisation ponds were constructed at Esholt sewage‐treatment works, Bradford. Each pond received screened sewage at different BOD loading rates over a two‐year period. Concentrations of BOD, SS, amm. N and chlorophyll‐a were measured weekly in summer and bi‐weekly in winter, and sludge accumulation was measured after 3, 9, 15 and 20 months. BOD and SS removals were consistently high, although they were lower in summer than in winter due to high levels of algae. The removal of amm, N was generally much better in summer than in winter ‐ the removal mechanism being most likely related to algal activities. Sludge accumulation rates were very low.

AbstractThe microbiological requirements for enhanced treated sludge in the Safe Sludge Matrix are reviewed and compared with those for foods, which are much less stringent. Quantitative microbial risk analysis shows that the risks to human health from disease transmission through sewage sludge to grazing animals or food crops are very low, indicating that the strict requirements of the Safe Sludge Matrix are not really justifiable.

AbstractThe Burwarton Estate waste stabilization ponds, near Bridgnorth, Shropshire, serve a population of 150. There are three ponds in series: a facultative pond, and two equal maturation ponds, followed by two parallel and alternately used constructed wetland ditches. This paper describes the design of the ponds and reports upon their performance during the first two years of operation.

ABSTRACTWaste stabilization ponds are widely used in many European countries, such as France and Germany, for the treatment of wastewater from mainly small communities. There would seem to be no reason why they should not also be a suitable treatment process for populations of under 2000 in the UK. The relative advantages and disadvantages of ponds are compared to other small community treatment systems, such as rotary biological contactors, biological filters and reed‐bed systems, particularly in relation to effluent standards with respect to algae, nutrient removal and relative costs.