Abstract
The vertical flow constructed wetland (VFCW) has become an attractive decentralised technology for septage treatment. One of the main purposes of the septage treatment is to reduce the volume of raw septage through dewatering, where the solids content is retained in the wetland bed and the water content is released. The retention of solids forms a layer of sludge deposit at the wetland surface, and the drained water, the so-called leachate, typically contains a lower solids content. This article reports the performance of dewatering and filtration of a pilot-scale VFCW designed for septage treatment. A comparison between two feeding strategies, hydraulic loading rate (HLR) and solids loading rate (SLR), is presented. The dewatering efficiency through drainage was found to be dependent on the solids load. The removal of total solids (TS) and chemical oxygen demand (COD) were excellent as the quality of leachate showed that more than 90% of TS and COD were retained in the system. This study reveals that the feeding based on SLR delivered a more sustainable performance for dewatering and solids removal. The build-up of sludge deposit significantly deteriorated the dewatering efficiency through drainage, but it tended to improve the filtration capacity.
Highlights
The individual septic tank (IST) is the main on-site sanitation system that is used in both urban and rural areas of developing countries
The results presented in this article were obtained from the two phases of studies to evaluate the influence of solids loading rate (SLR) and hydraulic loading rate (HLR) to the dewatering and treatment efficiency in the vertical flow constructed wetland (VFCW) that is designed for septage treatment
The dewatering efficiency showed a dependency on the deposit thickness, where a thicker sludge deposit significantly reduced the amount of drained water
Summary
The individual septic tank (IST) is the main on-site sanitation system that is used in both urban and rural areas of developing countries. The sludge accumulated in the septic tank needs to be cleared periodically to maintain its treatment efficiency, and the mixture of sludge and blackwater removed from the septic tanks is known as septage. Septage management is still a challenge in developing countries [2]. In Sarawak, a state of Malaysia, there are more than 370,000 individual septic tanks in operation, which serve approximately 1.9 million people in the entire state [3]. There are three centralised septage treatment plants located in the cities of Kuching, Sibu, and Miri. One of the concerns of septage treatment in these less-densely populated areas is the long distance between the household and treatment plant
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