Chemically enhanced primary treatment of dairy wastewater using chitosan obtained from shrimp wastes: optimization using a Doehlert matrix design.

Dairy operations generate large volumes of polluted wastewater that require treatment prior to discharge. Chemically enhanced primary treatment (CEPT) is a widely utilized wastewater treatment strategy; but it requires the use of non-biodegradable coagulants that can lead to toxic-byproducts. In this study, chitin from shrimp shell waste is extracted and converted into chitosan. Chitosan was demonstrated to be a natural, low-cost alternative coagulant compatible with the CEPT. Following treatment, dissolved air flotation allowed for the removal of turbidity, COD, and UV254 from the synthetic dairy effluent (SDE). Doehlert matrix was used to optimize the chitosan dosage and pH of the CEPT; as well as to model the process. The mechanisms behind the coagulation-flocculation were revealed using zeta potential analysis. FTIR spectroscopy was utilized to confirm the functional groups present on the chitosan. Chitosan with a degree of deacetylation equal to 81% was obtained. A chitosan dose of 73.34 mg/L at pH 5.00 was found to be optimal for the removal of pollutants. Removals of COD, turbidity and UV254 were 77.5%, 97.6%, and 88.8%, respectively. The amount of dry sludge generated to treat 1 m³ of SDE was 0.041 kg. Coagulation-flocculation mechanisms involved in chitosan-mediated treatment of SDE involve the neutralization of electrostatic charges carried on the amine groups present in cationic chitosan at pH 5.00. Doehlert matrix proved to be a useful tool in optimizing parameters throughout the coagulation-flocculation process. Chitosan from shrimp waste is a low-cost, eco-friendly coagulant alternative for the removal pollutants from dairy effluent using the CEPT.

Assessment and optimization of the use of a novel natural coagulant (Guazuma ulmifolia) for dairy wastewater treatment.

A feasible, novel, and natural coagulant extracted from G. ulmifolia stem bark was characterized and used in experiments of coagulation/dissolved air flotation (C/DAF) to treat synthetic dairy wastewater (SDW). The performance of G. ulmifolia to remove turbidity, chemical oxygen demand (COD), and UV254 was evaluated by using response surface methodology (Doehlert matrix). G. ulmifolia dosage and pH were evaluated and optimized in the C/DAF process and its characterization was performed by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and also zeta potential. Results showed that G. ulmifolia stem bark is composed of large quantities of condensed tannins represented by the groups C=C-C and CO of pyran (flavonoid C-rings), which serve as bridges during coagulation. Moreover, the presence of porous cavities in surface of G. ulmifolia, shown by SEM, indicated capacity for adsorption. G. ulmifolia dosage and pH were significant (p ≤ 0.05) for pollutant removal from the SDW. Jar test results revealed that 95.8% of turbidity, 76.0% of COD, 81.2% of BOD, and 85.6% of UV254 were removed from SDW by using G. ulmifolia stem bark at a dose of 775.8 mg L-1 and pH 5.00. Finally, our results showed promising use of G. ulmifolia as a coagulating agent due to its novelty, efficiency, low-cost, and eco-friendly properties as an alternative for the treatment of dairy wastewaters.