Microbial Consortium–Based Conversion of Dairy Effluent into Biofertilizer

Dairy wastewater (DWW) is nutritionally rich and extremely hazardous to the environment if discharged untreated. The conventional treatment is time-, labor-, and energy-intensive. A tailor-made microbial consortium converted DWW into a biofertilizer with the ability to enhance biomass and yield in mung bean (Vigna radiata var. MEHA). The consortium produced ammonia from DWW at a rate of $1.65\times {10}^{-6}\mathrm{mol}{\mathrm{s}}^{-1}100{\mathrm{mL}}^{-1}$ within 16 h of incubation in a biofilm bioreactor at 37°C with highest production of $10.11\mathrm{mg}100{\mathrm{mL}}^{-1}$ demonstrating 41.83% nitrate and 45.83% phosphate removal. The scalability was tested at ambient temperature in a 72-L bioreactor with an ammonia production rate of $3\times {10}^{-8}\mathrm{mol}{\mathrm{s}}^{-1}100{\mathrm{mL}}^{-1}$. Irrigation using the treated effluent resulted in a 1.7-fold increase in biomass, 49-fold decrease in root nodulation, and 2.6-fold increase in seed yield in mung bean while providing protection from aphid (Aphis craccivora Koch) infestation. The total wastewater was converted into biofertilizer for use as a substitute for chemical fertilizer and fresh water for irrigation. This approach makes DWW management not only a zero-discharge process but also a self-sustainable one.