NATURAL SEWAGE TREATMENT IN THE UK: SELECTION GUIDELINES

ABSTRACT The 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.