Everytime you look up ...

Everytime you look up wastewater treatment plant design we see tank based activated sludge, MBBR, MBR, and all types of capital intensive treatment systems. While these systems can give high effluent quality than older lower costs systems, the idea of low cost, easy to operate wastewater treatment systems should not be forgotten. In the USA many people still rely on wastewater treated in aerated lagoons, trickling filters, facultative lagoons and constructed wetlands to treat domestic, food processing and even industrial wastewaters. The key reasons for using these lower tech systems include (1) lower construction costs, (2) less need for skilled operators, and (3) lower utility costs. The biggest downside is slightly lower treatment efficiency especially in colder climates and the need for larger foot print for the system.

Design criteria is still available in textbooks and governmental websites such as the US EPA.