Specifics of choosing technological solutions for small-scale wastewater treatment facilities

Summary

Small-scale wastewater treatment facilities have a number of features to be taken into consideration during design and operation. The process solutions for mechanical and biological wastewater treatment, as well as tertiary treatment and sludge processing are considered. Examples of facility calculations are provided outlining significant differences in the required layout and capacity of aeration tanks for different input loads. A biological treatment unit design with flexible control for variable input mass loads is proposed. A high probability of the need for dosing an external substrate source for denitrification is noted. Recommendations are provided for the design of small-scale treatment facilities of various capacities emphasizing that the operating depth of aeration tanks and secondary settlers is an important factor. Shallow depths (less than 2–2.5 m) increase the risk of biomass carryover and process disruption. In general, while selecting solutions for small-scale facilities, a combination of technological and economic criteria should be considered to ensure the facility is efficient enough with adequate capital and operating costs.

Key words

nitrification , denitrification , domestic wastewater , sewerage treatment facilities , small-scale structures , process volumes , substrate