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Industrial Wastewater Treatment
Published in Maulin P. Shah, Removal of Refractory Pollutants from Wastewater Treatment Plants, 2021
Activated sludge is an aerobic process for treating sewage and industrial wastewaters. As a suspended-growth biological treatment process, activated sludge uses a dense culture of microorganisms in suspension allowing the biodegradation of organic material under a steady oxygen supply and forming a biological floc for solid separation. Various aeration methods exist: diffused aeration, surface aeration, or pure oxygen aeration. This technique was developed at the beginning of the last century and is considered as an effective process for big cities as it can handle large amounts of effluent. This process is effective regarding the removal of organic contaminants. However, it is energy intensive and requires regular maintenance. Microorganisms accountable for treatment are maintained in suspension and a solid–liquid separation is completed in a secondary clarifier that follows the activated sludge process. Sludge and/or water is recirculated between the biological reactor and the secondary clarifier. Activated sludge systems are frequently used in combination with other treatment technologies such as membrane technologies. Activated sludge systems are typically located after the preliminary and primary treatment of wastewater and before the advanced tertiary treatment stage. Figure 2.3 presents a summary of the working principles for the activated sludge system.
Food Processing Wastewater
Published in Arun Kumar, Jay Shankar Singh, Microalgae in Waste Water Remediation, 2021
On discharging, this untreated wastewater with a high nutrient content could lead to eutrophic conditions in the receiving water bodies and streams; resulting in excess growth of blooms of the undesired algae or phytoplankton (Cai et al. 2013). In conventional methods, the activated sludge process is popularly used for the treatment of food processing wastewater. The activated sludge process involves physicochemical and biological operations (use of aerobic bacteria for degradation of organic matter). In this process, mechanical aeration is usually provided to the aerobic bacteria for the degradation of organic compounds. But these processes are inefficient in removing the inorganic nutrients (N and P) and further a huge amount of sludge is also generated. There are advanced processes such as filtration and reverse osmosis that could be used for effective treatment, but high investment and the need of skilled workers makes the wastewater treatment unaffordable and unviable for food processing industries.
Activated sludge
Published in Nick F. Gray, Water Science and Technology: An Introduction, 2017
Most problems associated with the activated sludge process involve poor settleability. Therefore, a rapid assessment method is vital to ensure good separation in secondary settlement so that the final effluent has a low suspended solids concentration, and that sufficient biomass is returned to the aeration tank. Two indices are widely used, the sludge volume index (SVI) and the stirred specific volume index (SSVI). The SVI is measured by filling a 1 L graduated glass cylinder with mixed liquor and allowing it to settle for 30 min. The volume of settled sludge (V) is then measured in mL and MLSS in mg L−1:SVI=V×1000MLSSmLg−1
Culturing the uncultured microbial majority in activated sludge: A critical review
Published in Critical Reviews in Environmental Science and Technology, 2023
Activated sludge is the most popular biological wastewater treatment application in the world and has been used for more than a century to treat a large variety of wastewater to protect the environment and human health (Beychok, 1967; Peces et al., 2022). With the complex sources of sewage (including rainfall, residential areas discharge, hospital wastewater, industrial wastewater, and farm wastewater), activated sludge contains abundant diversity of microorganisms. What’s more, as a classical wastewater treatment method, activated sludge contains plentiful functional microorganisms (Ioannou-Ttofa et al., 2017) that can remove pollutants in wastewater and transform them into harmless substances. These functional microorganisms play key roles in the ecological biogeochemical cycle and are thought to be important engines for elements energy flow on the Earth. Therefore, it is critical to decipher the ecology of the activated sludge microbial community that might bring new insights for future optimization of the biological wastewater treatment process.
Fenton process effect on sludge disintegration
Published in International Journal of Environmental Health Research, 2020
Activated sludge processes are an important technology for the treatment of wastewater. However, these biological processes produce a large amount of waste activated sludge (WAS) (Feng et al. 2009). In recent years, more importance has been placed on wastewater treatment processes to minimize waste sludge. This is due to the high cost of the disposal of WAS and the inadequacy of disposal areas. The treatment and disposal of excess sludge is approximately half of the total operating cost for domestic wastewater treatment plants (Odegaard 2004). For this reason, Fenton pretreatment (Liang et al. 2015), alkaline pretreatment (Li et al. 2009), ultrasound conditioning (Feng et al. 2009), electrolysis (Zhen et al. 2013), disintegration by electrocoagulation (Yıldız and Oran, 2018), and mechanical disintegration (Lehne et al. 2001) were developed to reduce amount of sludge methods such as polyelectrolyte and surfactants (Yuan et al. 2011).
Monitoring a municipal wastewater treatment process using a trend analysis
Published in Environmental Technology, 2018
Jani Tomperi, Esko Juuso, Anna Kuokkanen, Kauko Leiviskä
The sludge age and sludge concentration, on the other hand, are controllable. Suitable sludge age and sludge concentration are maintained by removing part of the activated sludge regularly from the treatment process. The sludge concentration depends on the influent load and the sludge age. Incoming load is again partly dependent on the flow rate and the season of the year. The sludge age is also dependent on the season of the year because to ensure nitrification throughout the year it is controlled mainly based on wastewater temperature. The sludge age is one of the factors that determine which bacterial groups are dominant in the activated sludge and how the bacteria grow and form flocs. For example, if the sludge age is too high related to the temperature, the amount of filaments may increase which hinders the settleability and bulking may occur.