Applicability of nanofiltration in the carwash industry

摘要

The applicability of nanofiltration membranes to recycle wastewater in the carwash industry is studied.For a typical carwash,the actual wastewater purification installation allows recycling(part of)the wastewater to rinse the cars,but an additional 160 liter fresh water is needed on average per car.To reduce this amount of fresh water,a more advanced purification technique is needed,like nanofiltration.To study the feasibility of nanofiltration,filtration experiments with a hydrophilic(NF270)and a hydrophobic(NFPES10)membrane were performed with wastewater collected at two different stages during the actual purification process and with solutions containing one of three surfactants(one cationic,one anionic and one nonionic)which seem to be the most occurring in the wastewater.The best results were obtained for the hydrophilic membrane NF270,as this membrane has a high water permeability and a high relative flux(not much fouling)and it retains surfactants and organic components for more than 95%.Considering the three individual surfactant solutions,it can be concluded that the nonionic surfactant(the alkaline rim cleaner)should best be replaced by another surfactant as the permeate flux drops to 50% of the original water flux.A necessary condition to apply nanofiltration in the carwash industry is the possibility to clean the membranes after filtration.The original pure water flux of NF270 was obtained after rinsing the membrane with water during only 15 min.This rinsing procedure was not sufficient for the hydrophobic membrane NFPES10;foulants were removed only after an additional alkaline cleaning step during 30 min at an elevated temperature(313 K).The good performance of NF270 together with the ease of cleaning makes this membrane preferable to use in the carwash.