Field study comparing the effect of hydraulic mixing on septic tank performance and sludge accumulation

ABSTRACT

This study investigates the effect of hydraulic mixing on anaerobic digestion and sludge accumulation in a septic tank. The performance of a septic tank equipped with a hydraulic mixer was compared with that of a similar standard septic tank over a period of 10 months. The study was conducted in two phases: Phase-I – from May to November 2013 (6 months); Phase-II – from January to May 2014 (4 months). Hydraulic mixing effectively reduced the effluent biological oxygen demand (BOD) and total suspended solids, and reduced the sludge accumulation rate in the septic tank. The BOD removal efficiencies during Phase-II were 65% and 75% in the standard septic tank and a septic tank equipped with hydraulic mixer (Smart Digester™), respectively. The effect of hydraulic mixing reduced the rate of sludge accumulation from 0.64 cm/day to 0.27 cm/day, and increased the pump-out interval by a factor of 3.

KEYWORDS:

• Digestion
• mixing intensity
• sludge accumulation
• pump-out interval

Acknowledgement

The author would like to thank Eng. Gillian Dumencu and Eng. Wilf Stefan from Cleardord Industries Inc. for their input and technical support throughout the study.

Disclosure statement

No potential conflict of interest was reported by the author.

Funding

This study was funded by the Clearford Industries Inc. (Ontario, Canada).