Removal of surfactants in greywater using low-cost natural adsorbents: A review

Water scarcity problem due to both natural and human-made phenomenon is on the rise. Development and implementation of efficient and cost-effective methods to treat and reuse wastewater has become a subject of prime importance. Greywater constitutes approximately 70% of total wastewater from a household, if treated can address major water shortage problems. The current review is focused on the use of low cost materials as adsorbents for the removal of surfactants from gray water. Based on the literature survey, common adsorbents like wood and activated carbon have long been used as conventional adsorbents to remove typical greywater pollutants. In particular, waste materials as low-cost adsorbents tested in the past for the removal of surfactants, which constitute major proportion of pollutants in greywater, have been the focal point of the present study. The values of typical parameters of wastewater as studied by various researchers were closely observed and were found as pH 6.2-9.4, turbidity 20-444 NTU, total dissolved solids (TDS) 237-2385 mg/L, chemical oxygen demand (COD) 58-1340 mg/L, biochemical oxygen demand (BOD5) 42.1-6250 mg/L, TSS 25-1852 mg/L and surfactants 3-118 mg/L. Myriads of research have investigated the potential use of agricultural waste as cheap and natural adsorbents for the removal of pollutants from both industrial and domestic wastewater. The fact that some of such bio-sorbents have been tested specifically for removing surfactants from greywater makes it an untouched and naive field of research. Adsorbents that have been tested include granite sand, granular charcoal, dolochar, rice husk, coconut shell, zeolites etc. Such studies have not only portrayed a wide range of removal efficiencies but also depicted a pH dependent adsorption process. In a nutshell, there is a tremendous scope to explore such cost-efficient and simple alternatives and subsequently be implemented in the near future.