Chunyou Zhu

Influence of process parameters on phosphorus recovery by struvite formation from urine

Batch experiments were conducted to examine the influence of various process parameters on phosphorus (P) recovery by struvite formation from urine. The results showed that the Mg/P molar ratio is one of the most important parameters affecting P recovery. The Mg/P molar ratio of 1.3 was found the most reasonable for struvite formation, and the P removal efficiency reached more than 96.6%. An increase in pH of urine solutions from 8.7 to 10.0 did not significantly affect P removal, but the quality of crystal formed at pH 10.0 was poor based on scanning electron microscopy analysis. A longer mixing time positively affected struvite formation, and compared to without mixing, the P removal efficiency increased from 72.7 to 97.3% after 5 min of mixing. The addition of seed material had no influence on the P removal efficiency, but contributed to the formation of struvite clusters.

Effect of contact to the atmosphere and dilution on phosphorus recovery from human urine through struvite formation

Phosphorus (P) in hydrolysed urine can be recovered through struvite formation. In the present study, batch experiments were conducted to investigate the effects of contact to the atmosphere (i.e. open and closed) and dilution [Vurine/(Vurine+Vwater)] (i.e. 100%, 50% and 25%) on P recovery from fresh urine through struvite formation with the addition of magnesium chloride (molar ratios of Mg/P=1.3 and 2.0) after 32 d of storage. The P loss mainly occurred during the initial stages of precipitation with calcium and magnesium (5 d). The precipitates formed at the bottom of the jars were identified by X-ray diffraction to be struvite, hydroxyapatite and calcite. The results showed that the P recovery efficiency from urine solutions in open jars was lower than that in closed jars. It caused significant ammonia volatilization in open jars, resulting in higher nitrogen loss, lower pH values and lower supersaturation. The P recovery efficiency decreased with dilution, which is related to lower pH and lower supersaturation resulting from water dilution. An increase in the Mg/P ratio from 1.3 to 2.0 enhanced P recovery to some extent in urine solutions with different dilutions. The largest P recovery efficiency was 93.7% and 97.3% at an Mg/P ratio of 1.3 and 2.0 for the 100% urine solutions in closed jars, respectively. Scanning electron microscopy revealed smaller struvite particle sizes at lower dilutions (100% and 50% urine) compared with higher dilutions (25% urine).

Removal of fluoride and total dissolved solids from coalbed methane produced water with a movable ultra-low pressure reverse osmosis system

Abstract The aim of this project was to establish an economical and environmentally benign technology for removing fluoride (F−) and total dissolved solids (TDS) from coalbed methane (CBM) produced water. The proposal involved a movable wastewater treatment system comprised of a flocculation sedimentation pretreatment unit and an ultra-low pressure reverse osmosis unit in Liulin County, Shanxi Province, China, where concentration of F− ranged from 1.3 to 18.2 mg/L and concentration of TDS ranged from 2800 to 6,600 mg/L. When the hydraulic load was 2–4 m3/day with the running mode in 10 h cycles at 10–15 days interval, the removal efficiency was 94.7% for F− and 98.1% for TDS with 55% water recovery from June to November 2011. Concentrations of F− and TDS in effluent were lower than the permissible discharge standard values of pollutants for irrigation and livestock. The flexible deployment and small footprint affordable was appropriate for removing pollutants from CBM mining areas with low water productio...