Hotta S, Funamizu N
Department of Environmental Engineering, Graduate School of Engineering, Hokkaido University, Kita-13, Nishi-8, Sapporo 060-8628, Japan.
Water Sci Technol. 2008;58(6):1187-92. doi: 10.2166/wst.2008.349.
Inhibition factors of urea hydrolysis caused by fecal contamination as source of urease were investigated. The urea hydrolysis was described by initial ammonification rate (IAR). Three factors for the inhibition (pH, free ammonia nitrogen (FAN) and salinity) were investigated in this study. It was found that the optimum pH value for the urea hydrolysis was obtained at pH 7 (30 degrees C). Similar results were obtained from pH 5 to pH 8 whereas pH 9 provided a little amount of negative effect on the hydrolysis. Significant effect of the FAN as inhibition factor on the urea hydrolysis was obtained in the urea solution: the hydrolysis was observed within 120 mg-N/l of the FAN level in artificial urea solution with fecal contamination. However in storage process of real urine the urea hydrolysis was observed until the FAN level increased up to 2,000 mg-N/l. Salinity obviously provided negative effect on the urea hydrolysis in stored urine with fecal contamination at 30 degrees C. It was assumed that high concentration of the NaCl (150 g/l) was required to achieve 50% reduction of the IAR.
研究了作为脲酶来源的粪便污染引起的尿素水解抑制因素。尿素水解通过初始氨化速率（IAR）来描述。本研究考察了三个抑制因素（pH值、游离氨氮（FAN）和盐度）。结果发现，尿素水解的最佳pH值在pH 7（30℃）时获得。在pH 5至pH 8时得到了类似的结果，而pH 9对水解有轻微的负面影响。在尿素溶液中，FAN作为抑制因素对尿素水解有显著影响：在有人粪便污染的人工尿素溶液中，当FAN水平在120 mg-N/l以内时观察到水解。然而，在实际尿液的储存过程中，直到FAN水平增加到2000 mg-N/l才观察到尿素水解。在30℃下，盐度对有人粪便污染的储存尿液中的尿素水解有明显的负面影响。据推测，需要高浓度的NaCl（150 g/l）才能使IAR降低50%。
