Extraction of nitrogen and phosphorus from the wastewater of municipal treatment facilities

Abstract

The article presents a new solution to reduce the load of phosphorus and nitrogen on urban wastewater treatment plants, basedon the use of semi-burnt dolomite to extract these elements from sludge waters. The efficiency of the proposed method is compared with existing purification technologies using the example of the Minsk wastewater treatment plant. The methods for determining the concentrations of phosphate phosphorus and ammonium nitrogen in model and real wastewater samples are described in detail. The analysis of model data simulating various pollution scenarios made it possible to evaluate the efficiency of phosphorus and nitrogen extraction using various reagents. The study takes into account all key return flows of wastewater treatment plants, including silt ponds, water after compaction of activated sludge and fugate after sludge dewatering. Daily material balances for total nitrogen and total phosphorus have been developed for a comprehensive assessment. Experimental studies with fugate obtained after dehydration of sediment with pretreatment with polyelectrolyte have confirmed the effectiveness of semi-burnt dolomite for the extraction of phosphorus and nitrogen, which opens up prospects for obtaining phosphorus-containing fertilizers. The dependence of the degree of extraction of phosphates and ammonium nitrogen on factors such as pH and the initial ratio of concentrations of these elements in the return streams was revealed. The results obtained indicate the high efficiency of using semi-burnt dolomite to reduce the load on wastewater treatment plants and create conditions for the production of environmentally friendly fertilizers. This scientific researchis of high practical importance and contributes to the development of resource-saving and environmentally friendly wastewater treatment technologies.