The role of clogging in intermittent sand filter (ISF) performance in treating rural wastewater retention pond effluent

Biosand Reactors for Municipal and Industrial Wastewater Treatment: Status Quo, Challenges and Opportunities

“…Most of the laboratory column experiments and pilot BSR systems were operated intermittently or semi-continuously to mimic the inflow patterns of the WW in the 'real world' or to facilitate oxygenation. It has been shown in CW/TWs and BSRs that ingress of oxygen (O 2 ) via artificial aeration or intermittent operation promotes aerobic biodegradation and nitrification [42,54]. For instance, Ha and Ong [52] used artificial aeration and effluent recycling to create oxic (5 mg/L dissolved O 2 ) and anoxic zones for effective nitrification and denitrification, respectively.…”

“…Although the functional biomass can significantly reduce the HC of BSRs, this should arguably not be labelled as "clogging" unless the HC is reduced to below functional levels [16,18,56]. The biomass-associated reduction in HC is negatively correlated with the OLR because the heterotrophic microorganisms are reliant on organic substrates for growth [16,26,46,54]. Reductions in HC can therefore be reversed during periods of low organic loading [16,26].…”

“…Reductions in HC can therefore be reversed during periods of low organic loading [16,26]. There is an inflection point where the loading rates become insufficient to support microbial growth in the deeper layers of BSRs [54]. In systems operated at high OLR/HLR, substrate availability and biomass abundance are found in a continuum from the surface downwards [54,62].…”

“…There is an inflection point where the loading rates become insufficient to support microbial growth in the deeper layers of BSRs [54]. In systems operated at high OLR/HLR, substrate availability and biomass abundance are found in a continuum from the surface downwards [54,62]. Conversely, in BSRs operated with low HLR, such as those treating household sewage, the biolayer is formed on the surface [2][3][4]46,54].…”

“…In systems operated at high OLR/HLR, substrate availability and biomass abundance are found in a continuum from the surface downwards [54,62]. Conversely, in BSRs operated with low HLR, such as those treating household sewage, the biolayer is formed on the surface [2][3][4]46,54]. This 'schmutzdecke' decreases ingress of WW into the substratum but can also increase and stabilize removal performance.…”