Study On Drinking Water Security On Water Treatment By Activated Carbon Process

Drinking source water pollution is one of the main problems ranged from the whole world which is difficult to resolve by traditional water treatment. The primary task is to provide high quality water and safe drinking water and to verge on international drinking water standards. Combined activated carbon technology has become one of the most general and effective methods to remove pollutants by its remarkable advantages. The adsorption and biodegradation of activated carbon improves pollutants removal rates and the employment of ozone enhances them also. Even then as this technology itself and its biological security, a good many problems are expecting to be resolved and improved.This research aims to the leading reasons, the effect factors and the evaluationguidelines affecting the biological security of activated carbon effluent including thesize distribution and quantitative change of particles in drinking water treatment foractivated carbon; the factors affecting particles in AC effluent with different columnsand combinations; the size distribution, quantitative change and effect factors ofcarbon fines in drinking water treatment for activated carbon; the principle, operationcondition and combinations of desorption reagents of separation technology aboutfines and bacteria; inhibition to disinfection of traditional disinfector to fines withbacteria; effect of bacteria in AC effluent with biomass and bio-activity and particles.About 10 months experiment of activated carbon for removing pollutants indicatesthat the average total amount of particles (> 2μm) is of 27 ind./ml with the sizedistribution between 2μm and 15μm in the sand filter effluent during a filter cycle.The amount of particles with size beyond 2μm is more in the initial filtrated water andthat is more than 50 ind./ml in the initial 10 min. The amount of particles decreases atthe beginning and then raises during the experiment. Meanwhile outlet particles are3-6 times than inlet of BAC, 2-5 times than inlet of GAC. Particles of≤2μm are themost, 70% of total number, and particles of 2-5μm are determinative factors. Theoutlet and inlet particles are obviously changed by temperature with much higher regression coefficient. And under different temperature, the outlet particles are greater than the inlet commonly. Whereas the total amount of particles in the effluent is obviously increased by activated carbon filtration compared with that of sand filter effluent, the inlet particles significantly affect the outlet with average regression coefficient of >0.9. Comparing with different backwash process, experimental results show that the removal ratio of small particles is very low with air backwashing process simultaneously. The concentration of outlet particles is lower with water backwashing process simultaneously of low intension and long period.The experimental results show that the size distribution is between 0.45μm and 5μm, and the amount of fines is almost between 400 ind./ml and 600 ind./ml. Comparing with two carbon columns, the amount of fines with size beyond 5μm is almost same, of which the biggest discrepancy of the fines is 47 ind./ml, while the amount of fines with size below 5μm is different, of which the biggest discrepancy of the fines is 100 ind./ml. The amount of carbon fines is significantly influenced by the type of EBCT and backwash, and using the type of low EBCT and low strength and long lasting-time could effectively decrease carbon fines number. Carbon fines are little possessed of particles, and the ratio of≤2μm fines is just below 1% and≥3μm just 3%. The amount of fines doesn't accelerate along with the particles, and so the ratio is commonly lower than before. But bacterias in AC effluents often effuse with micro carbon fines.From the analyses of water quality in AC effluent, the results show that organisms with wave band of 200-300nm are less affected by carbon and column characteristics. The organism of 254nm has high removal ratio and the percentage is even about 50%. As a whole the organisms may contain conjugated double bond, phenyl, carbonyl and conjugated carbonyl. The AOC and Toxicity could influence the biotic security of product water.So the traditional experiment results indicate that outlet water quality is not safe enough although the traditional standard is coincident. The disinfection experiment with chlorine shows that the dosage of chlorine used in AC outlet is twice as that in sand filter outlet, which means particles in AC outlet inhibit the disinfection effect. And carbon fines show obvious inhibiting effect to the disinfector and the disinfection efficiency of bacteria absorbed fines of 0.8-5μm is about 40% from filtrating the AC outlet with micro-filter membrane and culture. Comparing with the effect of bacteria to bio-mass, bio-activity and particles concentration, the good pertinence is bio-mass, bio-activity and particles concentration respectively.