Slow sand filtration of secondary clarifier effluent for wastewater reuse.
Appropriate technologies are needed for disinfection of wastewater to allow safe reuse. Slow sand filtration is a simple technology used for pathogen and particle removal in drinking water purification. We investigated removal of fecal indicator bacteria relevant for wastewater reuse, particle removal, and runtime in slow sand filtration of secondary clarifier effluent. The key process parameters hydraulic loading rate, sand grain size distribution, and filter bed depth were systematically varied. Slow sand filters for tertiary treatment of wastewater seem promising for wastewater reuse, especially in arid developing countries. They eliminated 1.9-2.6 log10-units of E. coli and 1.9-3.0 log10-units of intestinal Enterococci reaching effluent concentrations of 11-142 CFU per 100 mL of E. coli and 2-24 CFU per 100 mL of intestinal Enterococci. Bacteria removal was shown to be a function of sand surface area, dirt layer, and supernatant water. Sand surface area per filter surface area should not be chosen below 2000 m2/m2. Slow sand filters removed 70-84% of total suspended solids reaching effluent concentrations of 1.2-2.3 mg/L and turbidity levels of 0.5-0.8 NTU. Average runtime was between 59 and 148 days.
Langenbach
K
K
Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Biotechnology, Permoserstr. 15, 04318 Leipzig, Germany. kilian.langenbach@ufz.de
Kuschk
P
P
Horn
H
H
Kästner
M
M
D019149:Bioreactors; D004203:Disinfection; D004926:Escherichia coli / Q000378:metabolism; D005243:Feces / Q000382:microbiology; D005374:Filtration; D009566:Nitrates / Q000737:chemistry; D010316:Particle Size; D010710:Phosphates / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012722:Sewage / Q000737:chemistry / Q000382:microbiology*; D012822:Silicon Dioxide; D014865:Waste Disposal, Fluid / Q000379:methods*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*
D009566:Nitrates; D010710:Phosphates; D000644:Quaternary Ammonium Compounds; D012722:Sewage; D014874:Water Pollutants, Chemical; D012822:Silicon Dioxide