| In China, water source distribution was widespread and the water resources were rich. But the per capita possession of water was little. And with the rapid development of economy, the pollution of water source was becoming more and more serious. Due to the rapid development of enterprises, more and more pollutants discharged into the water bodies.In urban areas, water treatment were draw more and more attention. However, the rural water treatment was relatively backward. People's environmental awareness was not strong. Water was not treated and used for civil usage and production. There were a lot of health and safety hazards existed.In most areas in China, pollutants in raw water bodies were simple. Ammonia nitrogen,organic matters and turbity were typical water pollutants. High levels of ammonia nitrogen in water would consume the dissolved oxygen so that aquatic organisms would die in huge numbers. While in the presence of nitrifying bacteria can form nitrate and nitrite nitrogen and it could accumulate in the human body and poisoning the human nervous system. High levels of organic matter in water, first it would affect the stability of water quality, resulting in large breed of autotrophic microorganisms in water, leading to the spread of diseases. Some organisms can produce biological enrichment from low concentration to form high concentrations, which gathered slowly in the human body, threats to human health. In the case of the low temperature, conventional water treatment methods were difficult treating water well and hard to meet drinking water quality standards.The ammonia nitrogen and organic matters contents were high in slightly polluted raw water. There were a lot of methods to remove organic matters and ammonia. However, according to the rural economic and technological conditions, cheap and effective processing method was more suitable for rural areas water treatment. Therefore, this study mainly used the method of biological filtration and gravity ceramic membrane in order to achieve the purpose of removing the main pollutants in water. According to the proposed rural water treatment project, this study was divided into four phases. Subject to the absorption characteristics of aerated biological filters, ceramic membrane filtration of slightly-polluted water at low temperature processing, provide the basis for joint operation treating slightly polluted raw water. The first phase of the study was to investigate adsorption properties of filters on ammonia nitrogen in low-temperature water. Through the dynamic and thermodynamic analysis, the process was single-layer adsorption and adsorption heat release. The process could also occur spontaneously at low temperature. In view of the limited absorption capacity of the natural filler and modification can improve the adsorption capacity of the filler, the zeolites and haydites were attached to be modified. Then modified zeolites and haydites were investigated in the same conditions.The static test showed that the dynamic equilibrium time of the modified zeolite and the modified zeolite was significantly shortened by 10-20 min, and the adsorption capacities were greatly increased.It showed that the modified filters adsorption capacities of ammonia nitrogen from water were greatly increased. The second phase was studied the bioaccumulation properties of modified filler in BAF. Results showed that the modified zeolite BAF and modified haydites BAF in the time required to complete start-up section respectively in 24 d and 28 d, while natural zeolites BAF and natural haydites BAF needed to complete the biofilm 30 d and 32 d. The modified zeolites BAF and modified haydites BAF shortened the start-up time in 6d and 4d. In the stable section, modified filter BAF outlet quality were superior to those of natural filter BAF outletr.After back washing, the modified haydites BAF and the modified zeolites BAF got recovered in 5h and 8h. The third phase was studied of inorganic ceramic membrane fluxes and water distribution height design and response surface optimization by BBD tests. The finalize the gravity of ceramic membrane water tank installation height was 1.0m and ceramic membrane back flush time for 3.5h. According to the degree of pollution of the ceramic membrane, the cleaning process was divided into water backwashing and organic solvent cleaning two kinds. When the influent turbidity was 10 NTU, after 10-14 times water backwashing, 200 nm membrane flux was declined 10.28% and 800 nm membrane flux was declined 7.80%. After the chemical cleaning, 200 nm membrane flux was 17.7 L/h?m2 and 800 nm membrane flux was 20.6 L/h?m2..In actual operation, according to the water quality characteristics of membrane Backwashing time requires further optimization. The forth phase was according to the results of the first three stages, modified filler BAF combined with gravity water ceramic membrane component to treat practical slightly polluted raw water at low temperature. It showed that when the influent ammonia concentration was above 3.0mg/L and permanganate index above 4.0mg/L, hydraulic residence time is extended to 2.5h allows the water to meet drinking water standards.When the influent ammonia concentration is less than 3.0mg/L, and the permanganate index less than 4.0mg/L, hydraulic retention time of 1.5h could ensure that ammonia concentration was less than 0.5mg/L and permanganate index was less than 3.0mg/L. The combined treatment can be used in slightly polluted raw water, which can provide the guarantee for the rural population's health and rural economic development. |
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