Suspended and waterborne polyurethane immobilized nitrifying bacteria have been adopted for evaluating the effects of environmental changes, such as temperature, dissolved oxygen （DO） concentration and pH, on nitrif...Suspended and waterborne polyurethane immobilized nitrifying bacteria have been adopted for evaluating the effects of environmental changes, such as temperature, dissolved oxygen （DO） concentration and pH, on nitrification characteristics under conditions of low ammonia concentrations. The results showed that nitrification was prone to complete with increasing pH, DO and temperature. Sensitivity analysis demonstrated the effects of temperature and pH on nitrification feature of suspended bacteria were slightly greater than those of immobilized nitrifying bacteria. Immobilized cells could achieve complete nitrification at low ammonia concentrations when DO was sufficient. Continuous experiments were carried out to discuss the removal of ammonia nitrogen from synthetic micropollute source water with the ammonia concentration of about 1mg/L using immobilized nitrifying bacteria pellets in an up-flow inner circulation reactor under different hydraulic retention times （HRT）. The continuous removal rate remains above 80% even under HRT 30 min. The results verified that the waterborne polyurethane immobilized nitrifying bacteria pellets had great potential applications for micro-pollution source water treatment.展开更多
In order to avoid the loss of ammonia during solar drying of stored urine, low-tech stripping is suggested as a pretreatment process for ammonia recovery. The mass transfer of ammonia from stored urine with an initial...In order to avoid the loss of ammonia during solar drying of stored urine, low-tech stripping is suggested as a pretreatment process for ammonia recovery. The mass transfer of ammonia from stored urine with an initial pH of about 9 was tested in a simple closed vessel operated at 72°C, 74°C and 85°C. The specific urine/gas interface was 16.97 m-1. For ammonia absorption, a beaker with sulfuric acid was positioned in the gas phase of the container. After keeping the stored urine for 73 h at 85°C, the concentration of free ammonia (NH3) was reduced by more than 99%, and the pH of the stored urine decreased to 6.4 due to ammonia volatilization. Total ammonia (NH3+ NH4+) concentration was reduced by only 83% in the same period. At lower temperatures, the process was slower. Required treatment time can be reduced when specific gas/liquid interface is increased. Because it is known that water can be heated in solar boxes to temperatures above 90°C, this simple stripping apparatus is feasible to be operated with solar energy in remote areas with suitable climatic conditions where no electric power is available. As the area demand for solar “low-tech stripping” is less than 1 m2 per capita, this process can be looked at as a suitable pretreatment of stored urine prior to solar evaporation.展开更多
文摘Suspended and waterborne polyurethane immobilized nitrifying bacteria have been adopted for evaluating the effects of environmental changes, such as temperature, dissolved oxygen （DO） concentration and pH, on nitrification characteristics under conditions of low ammonia concentrations. The results showed that nitrification was prone to complete with increasing pH, DO and temperature. Sensitivity analysis demonstrated the effects of temperature and pH on nitrification feature of suspended bacteria were slightly greater than those of immobilized nitrifying bacteria. Immobilized cells could achieve complete nitrification at low ammonia concentrations when DO was sufficient. Continuous experiments were carried out to discuss the removal of ammonia nitrogen from synthetic micropollute source water with the ammonia concentration of about 1mg/L using immobilized nitrifying bacteria pellets in an up-flow inner circulation reactor under different hydraulic retention times （HRT）. The continuous removal rate remains above 80% even under HRT 30 min. The results verified that the waterborne polyurethane immobilized nitrifying bacteria pellets had great potential applications for micro-pollution source water treatment.
文摘In order to avoid the loss of ammonia during solar drying of stored urine, low-tech stripping is suggested as a pretreatment process for ammonia recovery. The mass transfer of ammonia from stored urine with an initial pH of about 9 was tested in a simple closed vessel operated at 72°C, 74°C and 85°C. The specific urine/gas interface was 16.97 m-1. For ammonia absorption, a beaker with sulfuric acid was positioned in the gas phase of the container. After keeping the stored urine for 73 h at 85°C, the concentration of free ammonia (NH3) was reduced by more than 99%, and the pH of the stored urine decreased to 6.4 due to ammonia volatilization. Total ammonia (NH3+ NH4+) concentration was reduced by only 83% in the same period. At lower temperatures, the process was slower. Required treatment time can be reduced when specific gas/liquid interface is increased. Because it is known that water can be heated in solar boxes to temperatures above 90°C, this simple stripping apparatus is feasible to be operated with solar energy in remote areas with suitable climatic conditions where no electric power is available. As the area demand for solar “low-tech stripping” is less than 1 m2 per capita, this process can be looked at as a suitable pretreatment of stored urine prior to solar evaporation.
