The important role of expanded clay filter media in wastewater treatment
2023-09-13
Biological pretreatment with ceramsite is suitable for micro-polluted water sources in southern China and the renovation of old water plants. In China, many water plants have already built biological treatment facilities and put them into operation, while others are under trial or construction. Biological ceramsite pretreatment not only fully utilizes the removal effect of microorganisms on organic matter but also improves the reliability of drinking water brought by biological treatment, such as controlling microorganisms, particulates, and microbial metabolites after biological treatment through subsequent processes. Therefore, biological ceramsite pretreatment technology has a very broad development prospect in China.
Currently, there are the following issues in the application of ceramsite filter media.
1. The control level of pretreatment metabolites in subsequent treatment processes has not been deeply studied. The biological active products in biological ceramsite wastewater, such as endotoxins, soluble microbial products (SMP), and incompletely degraded organic compounds, have unclear health impacts.
2. Water temperature greatly affects the biological activity of biological ceramsite. Especially under continuous cooling conditions (≤5°C), the natural biofilm formation time on biological ceramsite is longer, and the treatment effects on COD_Mn and NH3-N decrease. Developing ceramsite using waste materials like fly ash can enhance the adsorption of organic matter in water and comprehensively utilize waste.
3. There are currently no reports on the regeneration of ceramsite filter media. It is recommended to strengthen research on ceramsite filter media regeneration to enable repeated use of ceramsite filter media and further promote its widespread application in actual production.
The main pathway for algae removal in biological ceramsite filter beds is inferred to be the bioflocculation, adsorption, and attachment of algae by the biofilm on the biological ceramsite filter media, which reduces the number of free algae in the water. The biofilm biologically oxidizes and decomposes attached algae and removes them through biofilm shedding (including natural shedding and backwash detachment) and sedimentation along with biological sludge discharge.
Biological ceramsite pretreatment has a high removal rate for blue-green algae and naked algae. The removal rate for green algae varies depending on the algae species and the proportion of different algae species. In other words, if the dominant algae in the water are species easily removed by biological treatment and they account for a large proportion, the overall algae removal rate by biological treatment will be relatively high; otherwise, the removal rate will be lower.
Main uses: Biological ceramsite filter media can serve as a biological biofilm carrier in high-load biological filter beds for industrial wastewater, micro-polluted water sources for tap water, biological filter beds for pretreatment, coarse materials for oily wastewater, ion exchange resin cushion layers, and microbial dry storage. It is suitable for advanced treatment of drinking water, with the ability to adsorb harmful elements, bacteria, and mineralize water quality. It is the best filter media for active biological degradation of harmful substances.
Biological ceramsite is a new type of biofilm carrier filter media, characterized by light weight, large specific surface area, and strong adsorption capacity. It is suitable for various forms of filter beds and tanks. Compared with quartz sand, its specific surface area is 2-3 times that of quartz sand of the same volume, and its porosity is 1.3-2.0 times that of quartz sand. Compared with sand filter beds, it has a higher average filtration rate (20-25 m/h), larger water output, longer filtration cycle, lower backwash frequency, and lower backwash intensity. It is made by selecting natural adsorbent materials and minerals, scientifically designing formulas, and processing through high-temperature sintering and fine screening. This filter media features light specific gravity, high porosity, good surface properties, high filtration rate, stable operation, long service life, low backwash water consumption, and rapid biological reproduction, making it an energy-saving and practical new type of filter media.
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