Water sustainability using pond-in-pond wastewater treatment system: Case studies

Wastewater is an easily accessible but highly underutilized resource that could meet irrigation needs while conserving freshwater for future generations and is increasingly recognized as an essential and economical strategy in areas with water scarcity. This paper presents case studies on the Pond-In-Pond (PIP) configuration where PIP is an integration of two types of pond – anaerobic and aerobic – and consists of a deeper inner section entirely submerged within the outer pond. Performance data from existing PIP, or PIP-like systems dated back to 1960s’, were collected and analyzed; and the results from the PIP systems investigated resulted in an average BOD removal of over 80 % with a deviation of less than 10 %. Consequently, the PIP unit alone ensured a level of treatment required for effluent reuse in crop irrigation for typical municipal wastewater with influent BOD in the range of 200–300 mg L⁻¹. Moreover, the combination of PIP with other processes in a treatment system has the capability of treating high-strength wastewater for other uses such as aquaculture, fishery, and others–including stream discharge. The PIP is a potentially viable and sustainable technology for low-cost wastewater treatment especially for reuse purposes due to the savings in capital costs, operations and maintenance costs, and revenue from reclamation of the effluent.