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ARS Home » Southeast Area » Stoneville, Mississippi » Cotton Ginning Research » Research » Publications at this Location » Publication #424036
Research Project: Development and Evaluation of Novel Technologies to Improve Fiber Quality and Increase Profitability in Cotton Processing

Location: Cotton Ginning Research

Title: Enhancing Dairy Wastewater Treatment: Effects of Hydraulic and Organic Loading Rates in Vermifiltration Systems

Author
item MIITO, GILBERT - University Of Idaho
item Alege, Femi
item NDEGWA, PIUS - Washington State University

Submitted to: Environmental Challenges
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2025
Publication Date: 6/10/2025
Citation: Miito, G.J., Alege, F.P., Ndegwa, P.M. 2025. Enhancing Dairy Wastewater Treatment: Effects of Hydraulic and Organic Loading Rates in Vermifiltration Systems. Environmental Challenges. 20(101207)/1-9. https://doi.org/10.1016/j.envc.2025.101207.
DOI: https://doi.org/10.1016/j.envc.2025.101207

Interpretive Summary: Systems that use earthworms and other organisms to treat wastewater have become common on dairy farms. They can also help farmers make more profit. This work studied how the hydraulic loading rates and organic loading rates affect the process. Testing included four loading rates. Materials tested include nitrogen, phosphorus, chemical oxygen demand (COD), earthworm biomass, and others. Results showed that the system reduced total nitrogen by up to 61%. COD was reduced by up to 51%. Lower loading rates achieved more reductions. An organic loading rate of about 2.5 kg COD per m² per day optimized the number and size of worms. Lower loading rates allow more time for the system to work and makes the system work better for dairy wastewater.

Technical Abstract: The expansion of the dairy industry, marked by the growth of large-scale farms and regional concentrations, has led to the generation of substantial manure volumes, posing significant environmental challenges if not effectively managed. Vermifiltration has emerged as a cost-effective and environmentally sustainable technology for wastewater treatment and nutrient recovery. This study aimed to evaluate the impact of hydraulic loading rates (HLR) and organic loading rates (OLR) on the performance of a vermifilter system treating dairy wastewater. Reduction efficiencies for total nitrogen (TN), total ammoniacal nitrogen (TAN), nitrate-nitrogen (NO3'-N), total phosphorus (TP), orthophosphate (ortho-P), chemical oxygen demand (COD), total solids (TS), total suspended solids (TSS), and earthworm biomass were assessed across four HLRs (0.5, 1, 2, and 3 m³ m'² d'¹) and corresponding OLRs (1.3, 2.5, 5.1, and 7.6 kg COD m'² d'¹). Results showed reduction efficiencies of 32–61% (TN), 20–71% (NO3'-N), 21–52% (TAN), 20–51% (COD), 24–33% (TS), and 42–74% (TSS), with significantly higher reductions achieved at lower HLRs (0.5 and 1 m³ m'² d'¹) and OLRs (1.3 and 2.5 kg COD m'² d'¹). The findings also indicate that an OLR of approximately 2.5 kg COD/m²/day is optimal for maximizing worm population growth and biomass accumulation in vermifiltration systems. The improved performance at lower loading rates was attributed to longer retention times, enhancing microbial and earthworm-facilitated degradation processes. Orthophosphate (ortho-P) reduction efficiencies, however, were higher at elevated HLRs, due to enhanced mineralization of organic phosphorus under these conditions. These findings demonstrate that maintaining low HLRs and OLRs is critical for optimizing the reduction of organics, solids, and nutrients in vermifilter systems treating dairy wastewater. The study provides insights for the design and operation of vermifiltration systems, emphasizing their potential as a sustainable solution for dairy wastewater management.