Investigation of anaerobic up-flow batch reactor for treatment of greywater in un-sewered settlements.

Abstract

Un-sewered settlements are provided with the basic water and sanitation systems that comprise, in most cases, of dry sanitation and standpipes. Substantial amounts of wastewater (including greywater) generated from households are discarded untreated into streets, open spaces between shacks, streams and rivers due to the lack of adequate disposal or treatment infrastructures. The negative impacts from unsafe disposal of greywater generated in un-sewered settlements affect both human health and the general environment. Several treatment technologies ranging from the simplest to the more sophisticated have been developed and made available for consideration to deal with the adverse impacts caused by the unsafe discharge of greywater. Some of these treatment technologies have been implemented successfully in certain developing countries worldwide. Amongst these is the anaerobic up-flow batch reactor (AnUBR) which was successfully used for the first time to treat greywater from sewered areas in Jordan, Lebanon and Sri Lanka. The AnUBR has emerged as a localised greywater treatment technology alternative to conventional treatment methods in areas not served by sewer networks. This technology holds promise because of its simplicity of design, high pollutant removal efficiency, absence of energy or chemical consumption, ease with which it can be implemented, cost effectiveness, and low operation and maintenance costs. This technology was originally developed for treating sewage and high strength greywater from hotels. Recently it was further pioneered by INWRDAM (Inter-Islamic Network on Water Resources Development and Management) in the treatment of greywater from sewered areas of developing countries. This technology has not been tested in un-sewered settlements of developing countries which are characterised by the lack of disposal infrastructures despite being suitable for tropical countries. This treatment system is able to produce effluent that meets the quality standard for discharge and irrigation. However, new applications of the AnUBR require further investigation in order to ascertain its feasibility and evaluate its performance in the un-sewered settlement context. Given the promising results reported for the AnUBR application for greywater treatment, this study aims to investigate the performance of the AnUBR as an alternative technology for the treatment of greywater generated in un-sewered settlements and its application in developing countries.

A laboratory scale plant encompassing the AnUBR was designed, constructed and investigated using influent greywater collected from two selected case study settlements representing sewered and un-sewered areas. The plant was operated for 20 consecutives days using greywater from both selected sites separately. The influent greywater was analysed prior to feeding the plant and fed intermittently by batch as per designed feeding schedule. The performance of the AnUBR was evaluated mainly by analysing the quality of effluent produced, while the typical application was recommended based on the ability of the plant to produce effluent complying with local regulations and ability to treat greywater regardless of its source. The daily characteristics of influent greywater from both sites during the period of investigation were found to be as follows: temperature: 24 – 29ºC, pH: 7.1 – 7.2, TSS: 117.72 – 2,246.6mg/l, TN: 5.66 – 12.29mg/l, TP: 12.27 – 116.46mg/l, COD: 223.17 – 1,135.32mg/l, BOD5: 98.0 – 383.6mg/l, O&G: 52.22 – 475.29mg/l, e-coli: 8.87x104 – 2.17x107cfu/100ml, and Faecal coliform: 1.49x105 – 2.41x107cfu/100ml. The AnUBR managed to treat greywater to a quality that comply with the general standards for discharge into natural water resources. The final effluent showed a significant decrease in the level of pollutants from the initial values presented above to the following: temperature: 27 – 29 ºC, pH: 7.1 – 7.2, TSS: 5.12 – 12.82mg/l, TN 0.91 – 1.09mg/l, TP: 0.93 – 7.47mg/l, COD: 24.67 – 40.45mg/l, BOD5: 8.59 – 16.0mg/l, O&G: 1.15 – 1.72mg/l, e-coli: 213.3 – 1.12x103cfu/100ml, and Faecal coliform: 461.6 – 1.5x103cfu/100ml. Results obtained showed that the quality of influent greywater (from un-sewered settlements) is similar regardless of the water and sanitation technology. Following the operation of the AnUBR, significant removal of pollutants was observed in all processes. The overall removal efficiency averaged 80 to 95% for O&G and TSS respectively and 50 to 85% for TN and TP. The COD and BOD5 removal averaged 70 to 85% while that of micro-organisms averaged 90 to 99%. However, despite the high removal efficiency recorded the AnUBR may still require a post treatment step in order to improve the quality of effluent. It was concluded that the AnUBR is a viable alternative greywater treatment technology for un-sewered settlements, households or businesses such as hotels and restaurants. The AnUBR is able of treating high polluted greywater to effluent of quality that meets the standards for discharge or reuse provided a post treatment to ensure the complete killing of pathogenic organisms. The result of this study confirms the performance of the AnUBR for the treatment of greywater and provides an understanding of its concept as an alternative to conventional treatment and its application in un-sewered settlements based on local practical investigations.