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Water Treatment
Published in Frank R. Spellman, The Science of Water, 2020
Another common filtration problem is associated with poor backwashing practices—the formation of mud balls that get trapped in the filter media. In severe cases, mud balls can completely clog a filter. Poor agitation of the surface of the filter can form a crust on top of the filter; the crust later cracks under the water pressure, causing uneven distribution of water through the filter media. Filter cracking can be corrected by removing the top 1 in of the filter media, increasing the backwash rate, or checking the effectiveness of the surface wash (if installed). Backwashing at too high a rate can cause the filter media to wash out of the filter over the effluent troughs and may damage the filter underdrain system.
Produced Wastewater Treatment Technology
Published in Frank R. Spellman, Hydraulic Fracturing Wastewater, 2017
Another common filtration problem associated with poor backwashing practices is the formation of mud balls that get trapped in the filter media. In severe cases, mud balls can completely clog a filter. Poor agitation of the surface of the filter can form a crust on top of the filter; the crust later cracks under the water pressure, causing uneven distribution of water through the filter media. Filter cracking can be corrected by removing the top 1 inch of the filter media, increasing the backwash rate, or checking the effectiveness of the surface wash (if installed). Backwashing at too high a rate can cause the filter media to wash out of the filter over the effluent troughs and may damage the filter underdrain system. Two possible solutions are to (1) check the backwash rate to be sure that it meets the design criteria, and (2) check the surface wash (if installed) for proper operation. The criteria ratings (high, moderate, low, none) for microfiltration/ultrafiltration systems in treating produced wastewater are as follows (Guerra et al., 2011): Robustness—highReliability—moderateMobility—highFlexibility—moderateModularity—high
Groundwater Remediation
Published in Kathleen Sellers, Fundamentals of Hazardous Waste Site Remediation, 2018
Solids in the influent gradually accumulate on the carbon bed, causing a pressure drop across the carbon. Large carbon adsorption units intended for long-term use are designed to permit periodic backwashing to remove particulates when the pressure drop becomes too high. Backwashing is generally necessary at a solids loading of roughly 1 to 3 lb/sf.59 When backwashing is to occur, treatment of contaminated groundwater must stop. Backwashing is accomplished by reversing the flow through the carbon unit, using clean water to expand the carbon bed and remove the solids. The wastewater generated from backwashing must be treated.
Experimental investigation on chemical clogging mechanism of loose porous media in recharge process of groundwater heat pump
Published in Environmental Technology, 2023
Jie Yang, Wei-xin Ren, Bo Kang, Yuezan Tao
In research on the prevention and control of recharge clogging [8,28–30], physical clogging was repaired via high-pressure backwashing and using lifting measures on the filter pipe. In addition, flocculants and disinfectants were added to the recharge water and cleaning measures related to these were taken to reduce biological blockage. For chemical clogging, oxidation corrosion of and iron hydroxide precipitation along the well tube wall could be alleviated using asphalt and antioxidation coatings. However, the problem of clogging during geothermal water recharge is widespread in the Guanzhong Basin in China, and the clogging of geothermal wells has been relatively serious in some places [31]. Relevant literature reported that the area was generally predominantly affected by chemical clogging, with the results indicating that this was related to high concentrations of related chemical components in the water and the regional porous thermal reservoir conditions; therefore, conventional oxidation prevention measures could not alleviate aquifer clogging [32]. Similarly, the recharge clogging of porous aquifers in Huaibei Plain, China, is also serious [33,34]; however, there have been few studies on this and the related clogging mechanism remains unclear.
Mature landfill leachate treatment in a biological filter using scoria as media
Published in Journal of Applied Water Engineering and Research, 2023
German D. Jojoa-Unigarro, Simón González-Martínez, Óscar González-Barceló
The pilot filter consists of a PVC pipe filled with lava stones. The effluent was placed 10 cm above the upper stone layers to allow treated wastewater to flow freely through the effluent pipe. Two effluent ports were set at 20 and 30 cm above the upper filter media layer, the first to collect backwash water and the other as emergency effluent. A diffuser was placed at the bottom of the filter to supply both low-pressure air for oxygen and high-pressure air for backwashing (Figure 1). An oxygen probe was installed under the upper water limit to monitor dissolved oxygen concentration and guarantee a minimum of 2 mg/L. Sampling valves were placed at 20 cm intervals. The main characteristics of the pilot filter and filter media are shown in Table 2. The filter media occupied a volume of 17.6 L and, when multiplied by the apparent porosity, the reaction volume (liquid among the filter particles) was 9.02 L.
Exploring the feasibility of dual media filtration at Morton Jaffray Water Works (Harare, Zimbabwe)
Published in Journal of Applied Water Engineering and Research, 2023
Zvikomborero Hoko, Brian T. Musima, Clarence F. Mapenzauswa
From the results, it has been observed that the adoption of dual media filters (DMF) has the potential of decreasing the headloss encountered in the filter beds when single-media filters (SMF) are used, thus reducing backwashing frequency. Zielina and Dąbrowski (2021) highlighted that the backwashing of rapid filters results in the consumption of treated water and energy. Therefore, the adoption of the DMF at Morton Jaffray Water Treatment Works (MJWTW) will likely result in a decrease in wastage of treated water and result in less energy being used as compared to when SMF are used thus reducing water treatment costs. Zielina and Dąbrowski (2021) also stated that backwashing contributes to the deterioration of the quality of the first filtrate if carried out very frequently, as is currently taking place at MJWTW. Therefore, the use of SMF will likely result in filters requiring sand replacement due to frequent backwashing compared to when DMF is adopted, resulting in increasing water treatment costs. However, the adoption of DMF is likely to have a higher initial capital cost compared to SMF due to the need for a deeper filter box for the DMF and cost of media.