Integrated Biological Approach in Dairy Wastewater Treatment: Removal of Organics, Nutrients and Solids

Abstract

Urbanization and industrialization have contaminated various water resources, but among all food industry dairy industry is one of the most water consuming industry. Million litres of dairy wastewater are generated daily during processing of various dairy products. In various stages of dairy products processing, it generates huge amount of wastewaters that contains organics, nutrients, fatty acids, proteins, total solids, etc in large concentrations. In view of this problem, present study aims to collect dairy wastewater and characterized to identify the toxic level and its problematic concern. Organics, nutrients and solids were selected as target pollutants whose remediation have been considered in various phases of this research work. Hydroponic rhizofiltration using Portulaca oleracea and Coleus scutellarioides with and without aeration were investigated in lab scale set up and proved successful in remediation of organics, solids and nutrients from dairy wastewater. Air circulation in treatment system empowered the process to dwindle total dissolved solids (TDS) (38.89-65.69%), total suspended solids (TSS) (30.78-79.04%), biochemical oxygen demand (BOD) (56.18-81.75%), chemical oxygen demand (COD) (43.67-79.46%), total phosphorus (TP) (34.36-76.35%), phosphate (34.58-79.46%), total nitrogen (TN) (30.47-74.88%). But in control system the removal is minimal and pH increases as compared to treatment system due to photosynthetic activity performed by macrophyte. The scanning electron microscope (SEM) of leaf and root of macrophyte identified accumulation of nutrients in leaf and root. But adsorption of nutrients and organics by root is more as compared to shoot. The FTIR and UV-VIS analysis of dairy wastewater before and after treatment also confirms remediation of organics, nutrients and fatty acids. Rhizofiltration in root of macrophyte prevent toxic substance to transfer to trophic level of plants and make macrophyte an appealing possibility for phytoaccumulation. Hence the dairy wastewater after treatment can be reused in irrigation purposes and the macrophyte, can be reused as cattle feed. Also, the study investigated removal of organics, nutrients and total solids from dairy wastewater using macrophyte assisted integrated vermifiltration with hydroponic system. The research exhaustively explains the remediation of COD (79.23-83.74%), BOD (79.31-89.34%), TSS (76.31-81.79%), TDS (71.19-86.40%), TN (72.96-81.05%), TP (76.35-87.67%), phosphate (76.72-78.77%) from dairy effluent. Earthworm and plant combinedly perform symbiotic and synergistic activity to avoid clogging in the system. The treated effluent contain phosphate which is better for irrigation purposes. The SEM analysis of sand, vermibed also confirms deposition of nutrients in filter bed. Wastewater after treatment contains humic substance which is confirmed by humic acid analysis. The FTIR and UV-VIS analysis of wastewater before and after treatment confirms the remediation of organics, nutrients and fatty acid from wastewater. The study helps to treat dairy wastewater as well as reuse wastewater in various purposes such as in irrigation purposes, industrial reuse and the macrophyte used in treatment process can be reused for cattle feed.