In-situ untilization of nitrogen-rich wastewater discharged from a biotrickling filter as a moisture conditioning agent for composting: Effect of nitrogen composition

Although the composting-biotrickling filter coupled system removed ammonia-based odor pollution, other pollutants (nitrogen-rich wastewater) arose. This study intended to determine the effect of in-situ disposal of different kinds of nitrogen-rich wastewater [i.e., multi-nitrogen (NH4+, NO2-, and NO3-)-rich (STL1), NO2--rich (STL2), and NO3--rich (STL3)] as a moisture adjustment agent during the composting thermophilic period on nitrogen transformation. Results indicated that nitrogen-rich wastewater addition did not impair the compost maturation, whereas raised the total nitrogen content of fertilizer by 15.8%-46.7% compared to the control group (i.e., tap water group). Moreover, adding STL1 has the potential to reduce CO2 and NH3 emissions and avoid incomplete organic nitrogen decomposition. Furthermore, nitrogen flow analysis unveiled that STL1 addition increased nitrogen content by strengthening ammonification, dissimilatory nitrite reduction to ammonium, and high-temperature nitrification pathways. Thus, in-situ disposal of STL1 from biotrickling filters via composting is a suitable technique for coupled systems to achieve zero discharge.

Automated summary

This study found that adding nitrogen-rich wastewater during composting can increase the total nitrogen content of fertilizer and reduce CO2 and NH3 emissions, thereby avoiding incomplete decomposition of organic nitrogen.