Evaluating the potential of anaerobic waste stabilisation ponds for wastewater treatment in a temperate climate

A pilot scale baffled anaerobic waste stabilisation pond (aWSP) was designed based on an organic loading of 0.17 kg COD m-3 d-1 to evaluate the potential of aWSP as a passive, sustainable technology for domestic wastewater treatment in temperate conditions. After 4 weeks of operation and up to 45 days (end of study), average removals of 37% COD, 30% BOD and 36% suspended solids were observed which compares to the literature surveyed for aWSP treating domestic wastewater. A linear correlation between COD removal and time since start-up was observed and compared favourably to an anaerobic membrane bioreactor (aMBR) that was started up unseeded. Seeding the aWSP apparently augmented start-up and whilst higher COD removal for aWSP have been reported, it is anticipated that continued operation (>45 days) will yield further efficiency improvements. Methane reported in the gas and liquid phase was approximately 4.1% and 5.7 mg l-1 respectively suggesting relatively low production of methane. However, this does demonstrate that methanogenesis occurred soon after start up. Using this data to model a 5000 PE site, total energy output of 62 MWhy-1 (electricity and heat) was generated and only 6 MWh y-1 (electricity) consumed, this compares to an equivalent conventional activated sludge process (ASP) which uses approximately 655 MWh y-1 electricity for aeration. Results to date suggest that aWSP technology represents a viable sustainable alternative for domestic wastewater treatment in a temperate climate versus traditional high energy technologies.