Practically, it is impossible to rebuild an existing
conventional septic tank into an ABR-septic tank, and
millions of the existing septic tanks in China are running
inefficiently. Therefore, a simple method to improve
the performance of a conventional septic tank is imperative.
Unfortunately, research in this field is lacking. YDT
(Yuhuan drawing three-dimensional)-carrier is a type of
three-dimensional elastic filler developed in Yuhuan town
in China. By adding YDT carrier into a conventional septic
tank (YDT-carrier-septic tank), the septic tank would turn
into a combined system, which contained both activated
sludge and biofilm. Therefore, it was selected as a potential
option to improve the performance of a conventional
septic tank.
Three septic tanks including a conventional septic
tank, an ABR-septic tank and an YDT-carrier-septic tank
were operated in parallel in the study. The objective was
to evaluate the feasibility of using an ABR-septic tank,
and using an YDT-carrier to improve the performance of
the existing conventional septic tank, at low-temperature
(16◦C) for on-site domestic sewage treatment. The performance
of the septic tanks, in terms of their COD
removal efficiency, hydrolysis, acidification and methanogenesis
ability and nutrient removal efficiency, was evaluated.
This investigation is crucial for the determination
of design parameters for retrofitting conventional septic
tanks to ABR-septic tanks and YDT-carrier-septic
tanks based on relevant local conditions and wastewater
characteristics.