Sorokhaibam Laxmi Gayatri - Green Approach to Dye Wastewater Treatment Using Biocoagulants

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      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.

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