The Experimental Study Of Modified Filter Media For Cellar Water Treatment Using Biology Slow Filtering Techniques

Northwestern China is dry and lacks water resources. The local residents in the ruralareas widely use the distributed water cellars to collect rainwater for daily use. Althoughwater cellars have basically solved the drinking problem, water with poor sanitation ispolluted in different degrees for rainwater directly flowing into the cellar: turbidity, ammonianitrogen, and organic content are all high, and bacteriological indicators greatly exceed thestandard. If not treated, cellar water can seriously harm people’s health, and it also has anegative influence on production and daily lives. Therefore, it is urgent to explore the newtechnology of the water treatment which is appropriate for the distributed water supply in therural area of Northwestern China, and to produce the corresponding water treatmentequipment, so that the local residents can have clean and pollution-free drinking water.Micro-polluted water can be treated effectively by using biology slow filteringtechniques. With the advantages of no dosage, low cost, convenient operation and simplemanagement, biology slow filtering techniques were chosen to treat cellar water for drinkingwater safety in the towns in Northwestern China. This thesis intends to combine filter mediamodification with biology slow filtering techniques. First, the filter was modified to determinethe optimal modification conditions. Then one slow filtration column was filled with themodified filter media. By the natural biofilm culturing, the contrastive analysis was madebetween iron-oxide-coated zeolites and common zeolites on the biofilm culturing and thetreatment effect of the cellar water. After stable operation, the influencing factors on theremoval rate of the two slow filtration columns were analyzed, in order to find out the bestoperating parameters. The impacts of filtration rate and break time were studied on the slowfiltering columns operation. Finally, the turbidity, ammonia nitrogen and CODMnremovalrates were studied on the real rain water.In the static test of filter media modification, the quartz sand and zeolite wererespectively modified with ferric chloride through heating to determine the best modificationconditions according to the ammonia nitrogen and CODMnremoval rate in the simulated rain.The results showed that: when the pH was7, the concentration of ferric chloride was2.5mol/L, the times of stirring was0, the calcination temperature was550℃, the calcination timewas3hours, and the coating times was2, and the best modified effect was achieved. Theammonia nitrogen and CODMnremoval rates of the two filter materials were improved aftermodification. Modified zeolite had better surface properties, larger adsorption capacity, andmore advantages than modified quartz sand. So modified zeolite was chosen as the filtermaterial in the slow filtration column. The results of dynamic test showed that: the slow filtering column filled with modifiedzeolite had the faster speed for membrane forming and higher removal rate of pollutants.Under stable operation, the average turbidity removal rate of the slow filtering column filledwith modified zeolite was96.67%, and the average turbidity of effluent was0.48NTU. Theaverage ammonia nitrogen removal rate of the modified column was86.63%, and the averageammonia nitrogen of effluent was0.112mg/L. The average CODMnremoval rate of themodified column was42.86%, and the average CODMnof effluent was2.61mg/L. All thewater quality indexes accorded with the Sanitary Standard for Drinking Water.When the influence factors were studied, the impacts of thickness of filter bed, filtrationrate, water temperature, influent ammonia nitrogen loading and CODMnloading on thepollutants were analyzed. The results showed: there were a positive correlation between theturbidity, ammonia nitrogen, CODMn, UV254removal rate and thickness of filter bed, and anegative correlation between the removal rate and filtration rate. The biomass became lesswhen the thickness of filter bed increased. Both the ammonia nitrogen and CODMnremovalrate of two columns increased with rising temperature. While the influent CODMnloadingincreased, the ammonia nitrogen removal rate decreased and vice versa. While the influentammonia nitrogen loading increased, the CODMnremoval rate decreased. When the influentammonia nitrogen loading was low, the ammonia nitrogen removal rate increased with theammonia nitrogen loading increased.The results of setting off for the slow filtering columns showed that: the recovery timewas one day for both the two columns after7days’ water-off. When the two columns werecut off for15days, the modified column’s recovery time was3days, the ordinary one’srecovery time was4days. All the removal rates were higher after cutting off.The turbidity and ammonia nitrogen removal rates of the real rain were uniformly likethe simulated rain, while the CODMnremoval rate of real rain was lower. The CODMnofeffluent can match the requirement of rural miniature centralized water supply and scatteredwater supply.