Dairy Effluent to Irrigation Water: A Holistic Bioremediation Process Using Microalgal Treatment

Abstract

Improper discharge of dairy wastewater in rivers and lakes without proper treatment causes environment pollution, contaminates water and has negative impact on human health. The high cost of nutrients and decreasing availability of fresh water are the major bottlenecks that currently hinder commercialization of microalgae. Dairy industrial waste water is one such source which when utilized for microalgae cultivation leads to bioremediation of waste water along with algal biomass. The development of rapid and cost effective cultivation methods of potential microalgae using industrial wastewater is still in nascent stage and must compete with the existing biological systems. A potential microalgal strain was isolated from dairy industrial effluent contaminated water and genetically identified as a close relative of Ascochloris sp (ADW007). Indoor microalgal cultivation studies were conducted in controlled conditions of light and temperature while outdoor pilot-scale experiments were performed in errant conditions using semicylindrical open barrels. The rate of biomass productivity of ADW007 was improved with raw dairy wastewater (RDW) as growth nutrient in indoor bench-scale (102.74±13.78 mg/L/d) and outdoor pilot-scale cultivations (206.19±4.59 mg/L/d) when compared with the algal growth in synthetic BG 11 medium (86±4.25 mg/L/d) and TAP medium (98.82±2.03mg/L/d), respectively. Similarly, in outdoor conditions the lipid content reached maximum to 35.1±2.65 % with volumetric and areal lipid productivities of 72.23±6.88 mg/L/d and 9.63±0.91 g/m2/d, respectively. With this the estimated annual algal oil production is nearly 31.4±2.99 KL/ha/yr or 20495±1953 gallons/acre/yr, if cultivated throughout the year. Post-harvesting process includes hollow fiber filtration followed by activated carbon treatment and resulted in 95±1%, 80±2 % and 99±0.3% reduction of Chemical Oxygen Demand (COD), nitrate and total phosphate (TP), respectively. The microalgal treated water was   suitable for irrigation and meet the standards of CPCB.