Research on Waste Stabilization Ponds in the United Kingdom: Sludge Accumulation in Pilot-scale Primary Facultative Ponds

Three pilot-scale facultative ponds, located at Esholt wastewater treatment works in Bradford, West Yorkshire, UK were operated in parallel for 53 months, each with different BOD loadings and hydraulic retention times. Measurements of the sludge accumulation were made at 6-monthly intervals commencing at 3 months after start-up. In addition grab sludge samples were collected and analysed for total solids, volatile solids and faecal coliforms. After the first year of operation the sludge accumulation rate was 0.74 m3yr−1 for all three ponds (p=816), independent of BOD loading and HRT; the per capita accumulation rates were within the range 0.08-0.16 m3 person−1 yr−1. Evidence of degradation was found in the sludge from the percentage of volatile solids in the dry solids, but insignificant removal of faecal coliforms.