Nutrient removal from digested swine wastewater by combining ammonia stripping with struvite precipitation
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Typical biological processing is often challenging for removing ammonia nitrogen and phosphate from swine wastewater due to inhibition of high ammonia on activity of microorganisms, exhaustion of time, and low efficiency. In this study, a physicochemical process by combining ammonia stripping with struvite precipitation has been tested to simultaneously remove ammonia nitrogen, phosphate, and chemical oxygen demand (COD) from digested swine wastewater (DSW) with high efficiency, low cost, and environmental friendliness. The pH, temperature, and magnesium content of DSW are the key factors for ammonia removal and phosphate recovery through combining stripping with struvite precipitation. MgO was used as the struvite precipitant for NH4+ and PO43− and as the pH adjusted for air stripping of residual ammonia under the condition of 40 °C and 0.48 m3 h−1 L−1 aeration rate for 3 h. The results showed that the removal efficiency of ammonia, total phosphate, and COD from DSW significantly increased with increase of MgO dosage due to synergistic action of ammonia stripping and struvite precipitation. Considering the processing cost and national discharge standard for DSW, 0.75 g L−1 MgO dosage was recommended using the combining technology for nutrient removal from DSW. In addition, 88.03% NH4+-N and 96.07% TP could be recovered from DSW by adsorption of phosphoric acid and precipitation of magnesium ammonium phosphate (MAP). The combined technology could effectively remove and recover the nutrients from DSW to achieve environmental protection and sustainable and renewable resource of DSW. An economic analysis showed that the combining technology for nutrient removal from DSW was feasible.
KeywordsDigested swine wastewater Struvite precipitation Stripping NH4+-N Phosphorus recovery Volatile solid
We are grateful to the Research Project of the State Key Laboratory of Food Science and Technology in Nanchang University (Project No. SKLF-ZZB-201722), the Key Project of Jiangxi Provincial Department of Science and Technology (20161BBF60057), the National Natural Science Foundation of China (21466022, 21878139), the Special Fund for the Jiangxi Province (GCXZ2014-124 100102102082) for financial support, and National Fund for study abroad.
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