Quality of greywater in Oman and its treatment using a sustainable system

Abstract

Oman faces the problem of water scarcity owing to the lack of rainfall which results in lower annual replenishment rates in contrast to the consumption rates, and hence requires effective water management. Ablution greywater (AG) is a potential greywater source in Oman as it is less contaminated and discharged in huge amount from mosques. Therefore, this study assessed the quality of AG in Oman to design a sustainable multimedia (sand and activated carbon) filter for its treatment. The coconut shell activated carbon was used in the filter as it provides an inexpensive option due to the huge availability of coconut shell waste in Dhofar region in Oman. All water quality parameters of AG were acceptable as per the Omani standards, except for TSS and turbidity. When compared with past studies in Oman, it was found that the characteristics of AG significantly change with time and therefore should be continuously monitored for effective treatment. The designed multimedia filter adequately removed TSS, turbidity, K, BOD5, Na, and Cl by up to 96, 96, 61, 50, 24, and 23%, respectively. Initially the concentration of NO3, SO4–2 and Mg significantly increased, however, later their concentrations started reducing with time. The treatment efficiency fluctuated with time concerning TDS and Ca. The quality of treated AG was not only in compliance with the Omani standards but also WHO guidelines to reuse wastewater for irrigation and toilet flushing. Moreover, by treating 63 m3 of water monthly, the filter can provide a yearly financial benefit of 519.14 OMR (approximately 1348.48 USD).