A Purification Technology Of Condensate In Space Station For Astronaut Daily Usage

The reuse of condensate in a space station is one of the guarantees for long-term manned orbital flight.As far as known,most existing condensate treatment processes are difficult to meet the needs of Chinese manned space-flight development with the disadvantages of low minerals,high energy consumption,many consumables and limited processing capacity.In this work,a new integrated process of "membrane bioreactor(MBR)+ nanofiltration(NF)+ reverse osmosis(RO)+ ion exchange + polyiodide disinfection + mineralization" is proposed to treat condensate in order to meet the astronauts' daily needs.The efficiency of this process was investigated through the laboratory research of each processing unit followed byintegration and optimization of the processing system.For the MBR unit,the effluent,pollutant removal efficiency and anti-fouling propertyof the three different membrane modules were compared.The results showed that the ceramic membrane had distinct advantages over the other two modules.Further optimizing operation parameters for the ceramic membrane was conducted.Under the optimal conditions(namely,membrane flux of 5 L/m2·h,stopping mode of 30 min/10 min,aeration intensity of 0.4 m3/h,HRT of 10 h),NH4+-N was lower than 0.2 mg/L,and TOC was lower than 4 mg/L in the effluent.For the NF unit,Vontron(VNF1-1812-75)membrane was the most suitable one among the tested modules to treat the MBR effluent which had excellent removal efficiency.The optimized condition was as following: the influent was 100 L/h and the operation pressure was 0.8 MPa.Under this condition,the NF effluent could meet the sanitary water.For the subsequent RO process,the suitable membrane components was Vontron ULP1812-50 membrane.Under the optimal operation conditions(namely,influent flow of 95 L/h,operating pressure of 0.6 MPa),the pollutants could be further removed,and TOC and NH4+-N was less than 1 mg/L and 0.2 mg/L,respectively.In order to meet the requirements of drinking water for astronauts,water treated by RO need further treatment of ion exchange to remove residue NH4+-N.The results showed that the combination of FPC22 Na cationic resin and NM60 mixed bed ionomer resin guaranteed the removal effectiveness of pollutants.To ensure the safety and health of drinking water,it is necessary to conduct disinfection and mineralization.MIR-B polyiodide resin was used as a disinfectant which had a good and continuous sterilization effect.Within the contact time of 40 s,iodine content in the effluent was 2 mg/L.Experiments using Maifanshi could adjust water from weak acid into weak alkalin with the contact time of 100 s.Based on the optimization of each unit,the above-mentioned units were systematically integrated and the continuous dynamic test was carried out for 80 days.The results showed that under the condition that was influent average TOC of 169.3 mg/L,NH4+-N of 40 mg/L,NF reflux ratio of 70%,the effluent from the NF unit could meet the requirements of sanitary water,and the effluent of the mineralized unit could meet the requirement of drinking water.