Swine Wastewater Treatment with Struvite Precipitation Technology

[Objective] This study aimed to determine the optimal technical parameters for the swine wastewater treatment by struvite precipitation. [Method] Central composite design （CCD） and response surface method （RSM） were employed to study the effects of struvite precipitation on removing the ammonia nitrogen in the swine wastewater. Quadratic model was developed to describe the mathematical relationships between the investigated factors of pH value, reaction time, magnesium to nitrogen molar ratio （Mg/P）, nitrogen to phosphorus molar ratio （N/P）, the investigated indicators of NH 4 -N removal efficiency and residual PO 4 3 -P concentration. Contour overlay plot was proposed to predict the optimal experimental conditions with the NNH 4 -N removal efficiency of 75% and residual PO 4 3-P concentration of 3.0 mg/L as the desired values. [Result] At pH of 10.0, mixing time of 30 min, Mg/N of 1.11, N/P of 1.14, the NH 4 -N removal efficiency （Y 1 ） was the maximum of 79.0% , and the residual PO 4 3-P concentration （Y 2 ） at this time was 0.35 mg/L. The verification test of the optimal conditions proved that the verification data and model predictions agreed well. [Conclusion] The optimized parameters for the chemical struvite precipitation used to treat swine wastewater with central composite experimental design and response surface method are scientific, rational and efficient.

Enhanced microalgae cultivation using digested kitchen waste sewage treated with struvite precipitation

This study demonstrated the feasibility of using struvite for nutrient management in algae cultivation on sewage wastewater.The results showed that struvite precipitation treatment dramatically reduced the ammonia in the digested kitchen waste sewage.The untreated sewage was unable to sustain continuous growth of algae,while the algae growth on the treated sewage was comparable with that on an artificial algae culture medium(BG11).The rapid growth on the treated sewage was accompanied by substantial removal of nutrients.The struvite precipitate recovered from the treated sewage was proven to be an alternative source of nitrogen,phosphorus and magnesium.The struvite precipitate was evidenced that it could substitute culture media in algae growth.This study showed that struvite treatment is viable for nutrient management of algae cultivation on sewage wastewaters which do not have suitable nutrient profiles.

Soil Chemical Property Changes over Time from Struvite Compared to Other Fertilizer-Phosphorus Sources in Multiple Soils

Studies have shown that phosphorus (P) recovered from wastewater as the mineral struvite [MgNH4PO4·6(H2O)] may be a viable alternative fertilizer-P source. This study aimed to compare the effectiveness of electrochemically precipitated struvite (ECST), reclaimed from synthetic wastewater, to other commercial fertilizer-P sources in cultivated soils from Arkansas [AR;silt loam (SiL) and loam (L)], Missouri (MO;SiL), and Nebraska [NE;SiL and sandy loam (SL)]. A plant-less, moist-soil incubation experiment, including ECST, chemically precipitated struvite (CPST), monoammonium phosphate (MAP), triple superphosphate (TSP), and an unamended control (UC), was conducted to quantify soil pH, nitrate (NO3-N), ammonium (NH4-N), and Mehlich-3 (M3)-P, -Ca, -Mg, and -Fe concentrations at 0.5, 1, 2, 4, and 6 months. All measured soil properties differed (P ·kg-1 for AR-L-TSP after 1 month and NE-SiL-MAP after 6 months, respectively. Soil M3-P ranged from -29.6 mg·kg-1 in the AR-L-UC after 1 month to 429 mg·kg-1 AR-SiL-TSP after 0.5 months. Results showed that, over time, ECST had comparable pH and soil NO3-N, NH4-N, and M3-P, -Ca, -Mg, and -Fe behavior compared to CPST, MAP, and TSP across various soil textures.

Struvite Recovery from Swine Waste Biogas Digester Effluent through a Stainless Steel Device under Constant pH Conditions

Objective To investigate the struvite precipitation under constant and non-constant pH conditions and to test a stainless steel device under different operating regimes to maximize the recovery of struvite. Methods The molar ratio of NH4^＋： Mg^2＋ PO43 was adjusted to 1： 1.2：1.2 and pH was elevated to 9.0. The absorbance measurement was used to trace the process of struvite crystallization. Wastewater and precipitate analysis was done by standard analytical methods. Results The pH constant experiment reported a significantly higher struvite precipitation （24.6±0.86 g） than the non-constant pH experiment （19.8±1.86 g）. The SAR ranged from 5.6 to 8.2 g m^-2h^-1 to 3.6-4.8 g m^-2h^-1 in pH constant and non-constant experiments, respectively. The highest struvite deposit on the device was found in regime 3 followed by in regimes 2 and 4. The highest PO4^3- （97.2%） and NH4^＋ （71%） removal was reported in the R1 regime. None of the influent Cu^2＋ or Zn^2＋ was precipitated on the device. Conclusion A higher struvite yield is evident in pH constant experiments. Moreover, the stainless steel device facilitates the isolation of heavy metal free pure （around 96%） struvite from swine waste biogas digester effluent contaminated with Cu^2＋ and Zn^2＋ and the highest yield is attainable with the device operating at 50 rpm with agitation by a magnetic stirrer.