Dependency on sea food has increased owing to its nutrition as well as being complete food. As the production of seafood is enhanced through aquaculture, wastewater release has also improved. The composition of wastewater from aquaculture production has been a concern as it has oil and grease, organic content, etc., which makes its treatment challenging. The present study aims at treating aquaculture wastewater using two natural coagulants—chitin and seeds of Moringa oleifera. The efficiency of the natural coagulants was compared against inorganic chemical coagulant ferric chloride. A blended coagulant with two natural coagulants seeds of Moringa oleifera and chitin was also tested. Jar test apparatus was used in the current experiments, and four coagulant doses were tested against 3 pH ranges, from 6 to 8. The study results showed that the coagulants showed a 30–50% reduction in various physicochemical parameters. Further, the most promising result was obtained with the blended coagulants (di-blend) with 70–81% removal of total nitrogen and total phosphorus and the highest reduction of chloride with 95%. The Fourier-transform infrared spectroscopy showed functionalized groups responsible for coagulation, and X-ray powder diffraction analysis of the blended coagulant indicated the crystallinity and amorphous nature of the compounds. Scanning electron microscope analysis presented a firm and dense structure indicating adsorption of impurities onto the coagulant. Thus, it is evident that natural coagulants can be the solution for the challenges of aquaculture wastewater and specifically the di-blend used in the present is ascertained to be a promising solution.

Coagulation is an essential and easy process to treat water and wastewater and also to adopt for point of use solutions. Coagulants have played a significant role in providing safe and potable water. Nevertheless, the ill effects of chemical coagulants, such as health effects and substantial sludge quantities, cannot be ignored. Under given conditions, the search for alternative coagulants has been the need of the hour, and researchers have presented those natural coagulants are promising alternatives. The exploration and evaluation of plant-based coagulants have shown that these are fit to substitute chemical coagulants sustainably. Previous studies have presented the efficacy of various coagulants but could not fill in the gap existing in terms of a cumulative database of natural coagulants. In these lines, the focus of the current review is to present the history of natural coagulants, the science involved and studies carried out to evaluate them at different levels. Furthermore, a cumulative database of 57 natural coagulants with their efficacy in removing impurities from raw water is presented.

Owing to the advantages of the natural coagulants under study, the present objective is to study the efficiency of blended coagulants: alum and chitin; alum and sago; and alum + chitin + sago. In this attempt, we have reduced the quantity of alum dose and added increasing quantities of the natural coagulants. The surface water samples collected from nearby sources were analyzed for the following parameters pre- and post-treatment with the coagulants. Coagulation and flocculation experiments were carried out using conventional jar test apparatus. Turbidity removal was observed to be nearly 99.29% at all pH ranges and doses. Removal of conductivity, solids and hardness was 58.83%, 32.03% and 33.33%, respectively. From the results obtained, it can be observed that the efficiency of blended coagulants in removal of various physicochemical parameters from the waters was better when compared to individual coagulants. The floc size in blend coagulants was larger than that of single coagulants. The data obtained in this study indicated the coagulation efficiency could be enhanced by using the blend coagulant.

Quality of water, along Mandal headquarters of a coastal district of Andhra Pradesh, India, was assessed prior to and past rainfall season to determine water's acceptability for consumption using water quality index (WQI). The present work involved collecting groundwater samples from Mandal headquarters' locations present in the entire district. All the samples were analysed in a comprehensive way for ten physicochemical parameters, including pH, magnesium, calcium, chloride, sulphate, nitrates, total dissolved solids, fluoride, potassium, and sodium. The geographical information system was used for mapping sampling sites. The coordinates of sample collection areas were recorded employing GPS. Correlation matrices for cation–anion were illustrated and from the qualitative results of the samples. Results indicate that WQI prior and past-rainfall seasons ranged from 37.53 to 312.46; 42.04 to 211.89 in 2016, while for 2017, these were in the range of 25.01 to 137.06; 30.06 to 228.83. The present study's WQI values indicate that the water samples possess poor quality, and no fluoride contaminations were observed. The analysis suggests appropriate treatment of sub-surface water from the study site before consumption.