Abstract
Laboratory scale rotating biological contactors were operated with synthetic wastewater to study the effects of the daily fluctuation of hydraulic and/or organic loadings as observed in wastewater treatment plants for small communities on the removal of organic substrates.
The following results were obtained.
1) Daily average effluent COD values observed in operations with varying inflow rate and strength of wastewater (variable loading) were higher than those of constant loading (no daily fluctuation of inflow rate nor strength of wastewater) with equivalent daily BOD and hydraulic loadings.
2) Little fluctuation in effluent COD was noted by the fluctuation of influent COD concentration under smaller constant flow rate, whereas the fluctuation increased with the increase in hydraulic loading.
3) Attached biomass observed in operations with variable loadings were smaller than those observed in constant loading operations with equivalent daily BOD and hydraulic loadings to high loading period of variable loading. This fact, i.e. the shortage of attached biomass, seemed to result in the higher effluent COD values during high loading period in variable loading operations and, as a consequence, the higher daily average effluent COD values.
