Processing and Disinfection of Sludge: Advantages and Disadvantages

LEADING IDEAS FOR SUSTAINABILITY IF(Impact Factor)12.87 ISSN-L 5547-7437 E-ISSN 5547-7437 INDIAN POPULAR SCIENTIFIC ONLINE JOURNAL INDEXED ON TOP BASES http://lifsindijourn.my-style.in/ Volume: 13 Issue: 13 May-2025 1 Processing and Disinfection of Sludge: Advantages and Disadvantages Karakalpak State University A.K.Sultonbergenova, bachelor's student in the field of "Construction and installation of engineering communications" During wastewater treatment at waste treatment facilities, impurities in its composition are separated. These sludges are trapped in primary sedimentation tanks, and during the biological treatment of wastewater, excess activated sludge is formed in biofilters, biolayers, and aeration tanks. Sludge discharged from the primary sedimentation tank is called “fresh.” It is brown in color, with a moisture content of 92–96%. The sludge contains helminth eggs; therefore, it must be processed and disinfected. To eliminate harmful and unpleasant odors, the sludge is fermented and decomposed by anaerobic bacteria. Facilities used for sludge treatment and disinfection include: - Septic tanks; - Double-chamber sedimentation tanks; - Sedimentation and digestion tanks; - Aerobic stabilizers. Since the treated sludge contains a large amount of water (95–98%), it is difficult to transport and use it as fertilizer. Therefore, dewatering of treated sludge is appropriate. For this purpose, the following equipment is used: - Centrifuges; - Sludge drying beds; - Flotation units; - Thermal treatment installations. One method of disinfecting sludge from municipal wastewater is aerobic digestion. In this method, microorganisms oxidize the organic matter of the sludge under aerobic conditions. This process is carried out in digesters known as metantanks. A metantank is a cylindrical or rectangular reinforced concrete structure. Its bottom is conical, and the top is tightly closed, with a special device installed at the LEADING IDEAS FOR SUSTAINABILITY IF(Impact Factor)12.87 ISSN-L 5547-7437 E-ISSN 5547-7437 INDIAN POPULAR SCIENTIFIC ONLINE JOURNAL INDEXED ON TOP BASES http://lifsindijourn.my-style.in/ Volume: 13 Issue: 13 May-2025 2 top to collect gases produced during the digestion process. The sludge in the metantank is mixed and heated using special equipment. For digestion, sludge from the primary sedimentation tanks can be fed into the metantank together with excess activated sludge and other organic materials after grinding. Sludge digestion in metantanks can be carried out under two temperature regimes — mesophilic (T = 33°C) and thermophilic (T = 53°C). The sludge is heated using steam or electrical equipment. The mixing of sludge is carried out by pumps, hydroelevators, or special mixers. According to their design, metantanks may have fixed or movable roofs. Sludge is loaded into the upper part of the metantank, while digested sludge is discharged from the bottom. Two-stage digestion can also be applied: the first stage is a closed heated metantank, and the second is an open unheated tank. In the second stage, sludge is thickened, and the solid part is separated from the liquid. Since the sludge discharged from digesters and other treatment facilities has a high moisture content, it is dried to make it easier to use. One of the drying methods is using sludge drying beds, where moisture content should be reduced to 75%. As a result, the sludge volume decreases by 3–8 times. Drying beds are classified as follows:- Natural drying beds;- Natural drainage beds;- Asphalt-concrete drainage beds;- Settling-type beds;- Surface water removal beds;- Compaction beds. In aerobic stabilizers, the sludge treatment process depends on the balance between activated sludge and sludge from the primary sedimentation tanks, as well as on their properties, concentration, and temperature. For aerobic stabilizers, aeration tanks with air supply systems are recommended. Aeration in stabilizers can be carried out using perforated pipelines or air diffusers. Their number and layout depend on the required aeration intensity and mixing efficiency. Mechanical and pneumatic aerators are not recommended because they can disrupt sludge structure and reduce water removal capability. The concentration of activated sludge fed into the stabilizer should not exceed 20 g/l, and the mixture of activated sludge and primary sludge should be within 25– 27 g/l. Activated sludge settled in secondary sedimentation tanks has a moisture content of 99.2–99.5%. Most of it is returned to the aeration tanks as return sludge. LEADING IDEAS FOR SUSTAINABILITY IF(Impact Factor)12.87 ISSN-L 5547-7437 E-ISSN 5547-7437 INDIAN POPULAR SCIENTIFIC ONLINE JOURNAL INDEXED ON TOP BASES http://lifsindijourn.my-style.in/ Volume: 13 Issue: 13 May-2025 3 Due to continuous microorganism growth, excess activated sludge is formed, which should be treated. Since excess sludge has high moisture, it is first thickened before being fed into metantanks. Various types of sludge thickeners are used for this purpose. For complete biological treatment of wastewater, radial thickeners are recommended, while for incomplete treatment, vertical thickeners are preferred. When designing sludge drying beds, the following parameters should be considered:- Working depth: 0.7–1.0 m;- Embankment height: 0.3 m higher than the working depth;- Minimum embankment width: 0.7 m (1.8–2.0 m if mechanical equipment is used);- Minimum slope of drainage pipes and channels: 0.01. References: 1. Baymanov I.K., Zakirov O.T. “Fundamentals of Water Supply and Sewerage Systems.” Nukus: Bilim, 2006. – 200 p. 2. Baymanov K.I., Shaniyazov G.T. “Operation of Wastewater Treatment Facilities.” Nukus: Karakalpakstan, 2008. – 32 p