| Our college dormitories water consumption is huge,and dormitory washing wastewater accounts for about 70% of total water consumption. Washing wastewater is superior drainage, with recycling value. In this study, sub-millifiltration module was used to treat college dormitories washing wastewater, to meet or close to the "Non- potable water for urban regeneration control of water conservancy projects and indicators limits "(SL368-2006) flushing standards.as flushing water, it can save a lot of water,reduce the discharge of wastewater and improve use efficiency.When the water temperature is 18℃, their resistance were within 1011 m-1,reducing 1 order of magnitude compared with membrane resistance. The intercept particle sizes of two module were 28.1,21.7μm by solute intercept method.Effects of module pore size and initial flux on the performance were investigated.Under different pore size conditions, the pore size larger, the greater filtration flux.the water turbidity, COD, LAS were also higher, and vice versa. The effluent quality of21.7μm module was better, but flux was less. Under different initial flux conditions,the initial flux larger, the greater filtration flux.the water turbidity, COD, LAS were also higher, and vice versa. The filtration flux didn’t increase unlimitedly, there was an initial flux limit.when the limit was reached, the filtration flux didn’t increase.the initial flux was about 99L/(m2.h), and sizes of the module was 28.1μm.when run25 min,the flux was about 30.4L/(m2.h), turbidity, COD and LAS were10.4NTU,134mg/L,3.71mg/L.the removal rate of turbidity,COD and LAS were 84%,53.4%, 48%.Foam separation was used as a pretreatment, the greater the intensity of aeration, the longer the time, the more foam produced, the higher the removal rate of turbidity, COD and LAS. When aeration intensity was 85 L/min, aeration time was2 min, the initial flux was about 215L/(m2.h), 5 minutes later, system pressure dropt to20 kpa, the effect was better.when run 25 min,the flux was about 78.4L/(m2.h),turbidity,COD and LAS were 11 NTU,98mg/L,5.5mg/L.the removal rate of turbidity,COD and LAS were 87%, 62.1%, 63.5%. The foam separation sub-millifiltration process compared with direct filtration process, the flux was greatly increased, and the effluent water quality was also improved.the foam separation sub-millifiltration process compared with coagulation-sedimentation process,its removal rate of LAS was higher, and turbidity and COD removal rate was relatively low, but its operation cost and used field area was less.its advantages were obvious,and more suitable for university dormitory toilet wastewater treatment.The methods of backwash were air scouring, water-wash and air-water backwashing. When air scouring was adopted, intensity for 300L/min, backwash time for 4min, permeability recovery rate of two modules reached the maximum,respectively were 98.1%, 96.7%. When water-wash was adopted, intensity for 1.3L/min, time for 2min, permeability recovery rate of 28.1μm module reached 100%;intensity for 1.3L/min, time for 3min, permeability recovery rate of 21.7μm module reached 100%. When air-water backwashing was adopted, air intensity for 300L/min,time for 2min, water intensity for 0.5L/min, time for 1min, by comparison,28.1μm module could be cleaned easier, and was the optimum pore size.Considering the flux and water quality, sub-millifiltration module optimum backwash frequency was 25 min,and it could run stably for 35 cycles or more. The hydrophilic modification of 28.1μm module surface was conducted by ethanol immersion method, respectively for 2 hours and 4 hours.the flux was improved compared to the unmodified module, and the turbidity was reduced compared to the unmodified module.Sub-millifiltration module could efficiently treat college dormitory washing wastewater.it had the advantages of less occupied area and operation cost, low noise,great research value of use. |
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