Publication Details (including relevant citation information):
Chethana, M, Sorokhaibam, Laxmi Gayatri, Bhandari, Vinay M, Raja, S, Ranade, Vivek V -
Abstract: The present study focuses on newer biocoagu-lants, bioformulations, and the understanding of coagulant behavior with biocoagulants in relation to chemical coagulants. Newer biocoagulants, seeds of Azadirachta indica (AI) and pads of Acanthocereus tetragonus, are discussed along with two known biocoagulants, Moringa oleifera and Cicer arietinum seeds. Dye removal studies were carried out using widely reported Congo red dye to facilitate easy comparison with other conventional coagulants and the effect of various parameters such as initial dye concentration, pH, coagulant dose, etc. are discussed in detail. The use of biocoagulant was found to be highly effective, and up to 99% dye removal was achieved for coagulant doses in the range of 300−1500 mg/L. It was also observed that coagulation is pH sensitive, similar to chemical coagulants. Although the biocoagulant dose is relatively higher than the conventional chemical coagulants, a good value for the sludge volume index, ∼50 mL/g for 1 h and 30 min, respectively, was obtained for the two coagulants, Acanthocereus tetragonus and Moringa oleifera. A very high particle count compared to chemical coagulants was observed using a focused beam reflectance measurement. Bioformulation with chemical coagulants such as alum, ferric, and aluminum based coagulants can, not only lower doses of biocoagulants (up to one-third) but can also result in significant improvement in the coagulation performance, up to 50% or more. Industrial wastewater treatment of dye wastewaters is a challenging problem, especially when the refractory pollutants are present that are difficult to degrade using conventional biological treatment methods, which are often reported to have inconsistency in quality and quantity of treatment. 1 Further, some of the dyes can cause serious damage to the environ-mental aquatic system and surrounding land. 2 Although, the discussion on the hazardous nature of these dyes is beyond the scope of this paper, it is important to note that despite the carcinogenic and mutagenic effects, over 50,000 tons of dyes are discharged into the environment annually. 3 The wastewater stream also contains metal pollutants such as copper, iron, and chromium, which has a cumulative effect and higher possibilities for entering into the food chain. The complex nature of wastewater is evident from the fact that it has a deep color, high concentrations of organics, high COD, and can have high ammoniacal nitrogen content, ranging from a few mg/L to 1000 mg/L or even more, apart from the presence of other inorganics/metals. In view of the fact that many dyes/textile and allied industries that produce or use these dyes generate huge volumes of wastewaters and limitations to the existing effluent treatment processes (either process or cost), it is imperative that newer methodologies be researched and applied suitably. Methods that align closely to nature are preferred in this regard since they can help maintaining ecological balance through the use of localized green resources for treatment. Thus, current practices require more technoeconomically feasible biological options, less generation of secondary waste, and improved methodologies to meet stringent pollution control norms worldwide.