Cost-effective phosphorous recovery from distillery wastewater using inherent nutrients: agronomic and economic assessment
摘要
Struvite crystallization effectively recovers phosphorus (P) from distillery wastewater but faces economic challenges due to required magnesium (Mg2+) additives. This study investigated the potential for cost-effective P recovery from real distillery wastewater by using its inherent Mg2+ contents. The recovery focused on the formation of calcium (Ca2+)/Mg2+ phosphates, particularly as struvite (MgNH4PO4). Visual MINTEQ was used to optimize six nitrogen-to-phosphorous (NH4+:PO43−) molar ratios to maximize P recovery efficiency. Condition 1 investigated wastewater’s inherent nutrient recovery potential, conditions 2–3 optimized NH₄⁺: PO43− ratios (1:1, 1.5:1), while conditions 4–6 balanced NH₄⁺: PO43− ratios with inherent Mg2+ (Mg:NH4:PO4 = 1:1:1. 1:1:2, and 1:1.5:1). Results showed higher Mg2+/ PO43− molar ratios increased P removal, while increase in NH₄⁺: PO43 ratio had minimal impact on P removal efficiency. Inherent nutrients (condition 1) yielded 21% PO₄3⁻ removal with 2.7 g L−1 recovery as struvite and hydroxyapatite, N:P = 1.5:1 (condition 3) achieved 65.6% PO43− removal while Mg2⁺: NH₄⁺: PO₄3⁻ = 1:1:1 (condition 4) removed 72.6%. ICP-OES analysis of precipitates (condition 1) showed supplementary fertilizer potential (P: 0.87%, N: 2.65%, K: 3.14%) with a good mix of macro- and micro-nutrients. However, substantial agronomic potential was observed in the precipitates of condition 3 (P: 6.05%, N: 4.96%) and condition 4 (P: 9.44%, N: 3.75%). Economic analysis for 90 m3 d−1 wastewater indicated a net financial return of $72 d−1. Our work highlights novelty in terms of utilizing inherent Mg2+ for cost effective P removal using inherent nutrients of real distillery effluents especially Mg2⁺ (whose dosage let alone costs 10% to 75% of struvite production) and also analyzed the agronomic potential of the recovered product for circular economy. Future research should focus on recovering pure struvite crystals and further include testing the precipitates in pot and/or field tests to validate the agronomic potential.