A low-cost municipal sewage treatment system witha combination of UASB and the “fourth-generation”downflow hanging sponge reactors

Abstract

This paper presents an evaluation of the process performance of a pilot-scale "fourth generation" downflow hanging sponge (DHS) post-treatment system combined with a UASB pretreatment unit treating municipal wastewater. After the successful operation of the second- and third-generation DHS reactors, the fourth-generation DHS reactor was developed to overcome a few shortcomings of its predecessors. This reactor was designed to further enhance the treatment efficiency and simplify the construction process in real scale, especially for the application in developing countries. Configuration of the reactor was modified to enhance the dissolution of air into the wastewater and to avert the possible clogging of the reactor especially during sudden washout from the UASB reactor. The whole system was operated at a total hydraulic retention time (HRT) of 8 h (UASB: 6 h and DHS: 2 h) for a period of over 600 days. The combined system was able to remove 96% of unfiltered BOD with only 9 mg/L remaining in the final effluent. Likewise, F. coli were removed by 3.45 log with the final count of 10(3) to 10(4) MPN/100 ml. Nutrient removal by the system was also satisfactory.

Use of G3-DHS Bioreactor for Secondary Treatment of Septic Tank Desludging Wastewater

“…The profile analysis of the wastewater stream along the height of the G3-DHS bioreactor treating desluging septic tank wastewater showed that soluble COD (organic substance) and ammonia were removed mainly in the upper portion (Figure 2). This finding has also similar presented by other studies [7], [6], [9], [14]. It could be implied that the microenvironment almost certainly differs along the bioreactor height.…”

“…The principal objective of this research is to evaluate the performance of the thirdgeneration of downflow hanging sponge (G3-DHS) bioreactor for treatment of desludging wastewater from IPTL. DHS bioreactor was originally published in 1997 by Machdar et al [5] and has been explored for extensive time by numerous researchers [6], [7], [8], [9], [10], [11], [12] for treatment of domestic wastewater.…”

Modification of DHS Bioreactor Module with Oil Palm Fiber Material for Treating Domestic Wastewater

“…Much of SS was entrapped in the fiber module and provided a long SRT. The performance was similar to that of the cube-type or the curtain-type DHS reactor (Machdar, 1997, Machdar, 2000, Tandukar et al, 2005. Time course of unfiltered COD and typical DO profile along the PF-DHS reactor height are shown in Fig.…”

“…One of the most important factors for aerobic reactors to achieve a good performance in treatment process is the DO concentration. DHS reactor has an advantage of needlessness of external aeration although being an aerobic system (Machdar et al, 1997;Tandukar et al, 2005Tandukar et al, , 2006. The DO level of effluent from the PF-DHS pilot plant was all the time kept around 6.3 mg/L (SD ± 0.8 mg/L) although the DO was 2.1 mg/L (SD ± 0.6 mg/L) at the inlet.…”

“…Since the development of the first DHS (Downflow Hanging Sponge) reactor more than a decade ago, it has been modified to make it simpler, cost-effective, and easy to maintain as well as suitable for real application in developing countries (Agrawal et al, 1997;Machdar et al, 1997;Machdar et al, 2000;Tandukar et al, 2005;Tandukar et al, 2006). Originally, the DHS reactor is constructed by cube-shaped polyurethane foam (PUF) sponges that hang freely in the air.…”