Meta-Analysis and Systematic Review of the Performance of Biological Processes in the Treatment of Organic Matter From Dairy Wastewater

Abstract

Dairy wastewater has raised many concerns because it is highly contaminated with high levels of organic matter. The major sources of contaminants in dairy wastewater are clean-in-place products, which are used to sanitize production lines, and whey, which is a byproduct of cheese and pressed yogurt. Various biological treatment technologies are suggested for the treatment of dairy wastewater. However, selecting the appropriate technology for dairy processes may be difficult, considering the multiple options available. Hence, 39 articles reporting various biological treatment processes were compiled to assess effective treatment technology. Four biological treatment processes, namely, constructed wetland (CW), algae technology (ALGAE), activated sludge technology (AS), and a combination of algae and activated sludge technology (AS + ALGAE), were assessed. A quantitative meta-analysis was used to compare the chemical oxygen demand (COD) removal efficiency of these technologies. The result indicated that there was no significant difference in removal efficiencies of all four processes; however, AS and Algae emerged as better technologies to treat high organic loading dairy wastewater. Although CW and AS + ALGAE were also shown to be effective, the studies assessed show that there's a significant difference in HRT of CW compared to other processes, with CW having the longest HRT (30.2 days). Moreover, there was also a significant difference in influent COD used in all studies that employed AS + ALGAE, with all the papers pooled in this technology using low organic loadings compared to the experimental studies of other processes. The results highlighted suitable biological treatment processes based on the dairy wastewater characteristics of the process.