Treatment of Pig Farming Effluents by Coagulation with Alkaline Wastes, Atmospheric Carbonation, and Bioremediation with Microalgae

Pig farming effluents usually present high levels of suspended solids as well as organic and biological contaminants that hinder the application of conventional treatment methods. Thus, novel treatment alternatives are needed to solve the problems of point source pollution arising from pig farms. In this paper, the integrated treatment of pig farming effluents was carried out using precipitation with wastes, atmospheric carbonation, and bioremediation with microalgae. First, different alkaline wastes (biomass ash, lime sludge and grits) were evaluated as coagulation agents. The raw effluent was diluted (1:5) and pre-treated via chemical precipitation at concentrations from 25 g/L to100 g/L. Biomass ash at the concentration of 100 g/L increased the effluent’s pH to 12.56 and allowed the highest removal of total solids (64.2%) and chemical oxygen demand (87.2%). After this step, the effluent’s pH was adjusted to 7 by atmospheric carbonation or the addition of concentrated H2SO4. The pre-treated effluent was then inoculated with microalgae cultures (Chlorella vulgaris and Tetradesmus obliquus; 10% v/v) to evaluate the removal efficiency of critical effluent parameters such as total solids, total nitrogen, total phosphorus, and chemical oxygen demand. The proposed integrated process enabled the treatment of pig farming effluents, achieving promising results for the reduction of critical parameters and promoting CO2 capture during atmospheric carbonation and microalgae growth.