With the growing shortage of freshwater resources and water demand increases, the number of water-free cities and regions can develop new sources of water use, wastewater recycling and reuse to solve water shortage has become one of the effective. Secondary treatment of urban sewage treatment plant effluent and water quality is stable, low levels of pollutants (0.1%), by conventional coagulation. Filter. Disinfection technology can meet the requirements for industrial circulating cooling water, which is part of the total urban water consumption accounts for water demand 1 / 3 . Fiber filter was recently developed an effective, economical filtration and recycling technology, has good filtering accuracy and stability of operation. In this study, fiber filters used in soft fibers for the filter media, use of filtering water and cleaning water pressure and direction changes, so that the fibers in filter automatically when pressed, automatically cleaning loose, to achieve the reuse of sewage purpose. Study in Shandong launched a municipal wastewater treatment plant, sewage plant secondary effluent reuse of direct filtration and flocculation, filtration of reuse.
1 Materials and Methods 1.1 Experimental Materials Dimensional workspace filter diameter 300 mm, high 1700 mm, allowable working pressure is less than 0.6MPa, medium temperature less than 60. Cylinder fitted with 22 bundles of nylon textile fibers, both ends of the barrel flower plate fixed on the top. With water, effluent, backwash water, backwash water, intake and exhaust 6 channels, can regulate the flow through the valve, install a pressure gauge, pressure test run. Equipment and work process diagram shown in Figure 1.
1.2 Analysis Water quality indicators prepared by the organization under the State Environmental Protection Administration, “Water and Wastewater Monitoring Analysis Method” for testing.
2 Results and discussion 2.1 Direct Filtration of Secondary Effluent
2.1.1 filtration rate and water quality
Taking into account the relative stability of water users, and easy-to-fiber filters the actual situation, compared to the device under different filtration rate direct filtration effluent water quality. The data in Table 1 shows the filter fiber filter over a wide speed range, in 10,20,30 m / h of filtration velocity, has good water quality, effluent SS were 10mg / L, and average removal rate of 60% above, the smaller the filtration rate, the effluent concentration. This is because the hydrophilic low flexibility, high fluffy fibers under the pressure to reverse the automatic compression, the formation of filaments closely interlaced filter layer. The thickness of the compacted layer thickness of only the filter a small portion of the upper part of the filter is relatively dense and the lower part of the loose, with the formation of a very good filter, so filter layer has a void the advantages of high filtration resistance, filter than surface area increases, the adsorption performance improvement, sewage interception capacity greatly increased. Even in the 30m / h of filtration velocity can effectively retain suspended solids in water and save them as high-speed shear flow caused by suspended particles penetrate the filter media. So is the water filter on the period of circulation of the head loss of filter layer to 0.06MPa for the backwash conditions.
Can be seen from Table 1, the filtration rate and filtration cycle has obvious relevance, the greater the filtration rate, filtration cycle shorter. Although the three kinds of filtration velocity, with equal water production facilities, but cycle length filter backwash effect device from water; and the filter velocity in smaller, more play fiber filter-storey volume of sediment characteristics. Therefore, the best filtration rate fiber filter selection should be based on local water conditions, water consumption compared to determine the size and other factors.
Fiber filter as the rejection of the SS, showing on the COD, BOD, TP, NTU, there are certain bacteria removal capability, removal rates reached 10% to 80%, 21% ~ 50 %, 11% to 81%, 52% to 85% and 87%; but NH 1 N, no effect on the removal of hardness. For reuse in terms of industrial cooling water, COD, BOD, TP, NTU, reduce bacteria that can effectively control calcium phosphate and accumulation of slime, reduced the amount of scale inhibitor and fungicide H. In order to verify the stability of the filter, select any of the running cycle tracking and detection (Figure 2). Be seen from Figure 2, the influent SS, NTU fluctuate within a certain range, but the concentration of the effluent stabilized at a lower value. Although carried out with the filter, sS and NTU have a slight upward trend, but the overall rejection of pollutants to be effective. And the higher the influent concentration, the greater the removal. Therefore, an alternative to traditional quartz fiber filter sand filter wastewater reuse is technically feasible.
2.1.2 outage on the impact of produced water
Fiber filter is simple, easy to maintain the advantages of the device can be kept full of water when the outage. Unfortunately, the result, the device stops after the restart 2d, a marked deterioration in water quality, and obviously the smell of corruption in the sludge. As previously suspended solids trapped in the filter layer reaction occurred in anaerobic sludge spoilage, resulting in soluble organic matter and nutrients, resulting in re-running the water COD, BOD and TP increased the concentration of a large number of seriously affected water security. Therefore, the device restarts after shutdown should be retained control of the sludge in the anaerobic reaction occurred before the long-term if they are not running, you should clean fiber filter, and treated with pesticides, washing with water saving.
2.2 Flocculation and Filtration of Secondary Effluent
To further enhance the filtration of the effluent quality and ensure water security, of the flocculation, filtration technology, reuse effect. Experiments in the filtration rate 20m / h under the conditions of work, the pharmaceutical use of common water treatment coagulant aluminum sulfate.
2.2.1 coagulant dosage on effluent water quality
Agents not only affects the amount of effluent water quality, but also determine the cost of water treatment. In order to determine the appropriate pharmaceutical dosage compared 0,10,20,30 and aluminum sulfate 40mg / L to run under the effect of dosage. Water and chemical reaction time was 20min, to form a larger floc size. In the 20 m / h of filtration velocity, the devices are continuously running 8h, water quality analysis for the sample average, the results shown in Figure 3.
Can be seen from Figure 3, adding aluminum sulfate to improve the water quality of water, but the larger dosage, SS, COD, TP and NTU and other lower effluent concentrations. This is because the aluminum sulfate dissolved in water, aluminum ions react with water, hydrolysis, and is accompanied by polymerization to form a variety of single-nucleon and multi-nuclear complexes. As most of the complex surface with positive charge, the original water, contains negatively charged suspended particulates (colloidal material, water, SS, COD, TP, NTU part) by its absorption, resulting in coagulation. When the charge was in and the particulate together with each other BOLA TANGKAS