Nonoxidative removal of organics in the activated sludge process

Abstract

The activated sludge process is commonly used to treat wastewater by aerobic oxidation of organic pollutants into carbon dioxide and water. However, several nonoxidative mechanisms can also contribute to removal of organics. Sorption onto activated sludge can remove a large fraction of the colloidal and particulate wastewater organics. Intracellular storage of, e.g., polyhydroxyalkanoates (PHA), triacylglycerides (TAG), or wax esters can convert wastewater organics into precursors for high-value products. Recently, several environmental, economic, and technological drivers have stimulated research on nonoxidative removal of organics for wastewater treatment. In this paper, we review these nonoxidative removal mechanisms as well as the existing and emerging process configurations that make use of them for wastewater treatment. Better utilization of nonoxidative processes in activated sludge could reduce the wasteful aerobic oxidation of organic compounds and lead to more resource-efficient wastewater treatment plants.

Approaches to energy and resource recovery from municipal wastewater

“…The high rate activated sludge (HRAS) process offers a technical option for capturing particulate, colloidal and soluble organic matters from municipal wastewater via biosoprtion and bioaccumulation. As a result, a large amount of sludge is expected to be produced and can be further subjected to AD for biogas generation (Modin et al, 2016). In fact, the working principle of HRAS is built on the philosophy of maximizing capture of particulate, colloidal and soluble COD, with minimized hydrolysis and mineralization of wastewater COD.…”

“…In fact, the working principle of HRAS is built on the philosophy of maximizing capture of particulate, colloidal and soluble COD, with minimized hydrolysis and mineralization of wastewater COD. For this purpose, a shorter hydraulic retention time (HRT) and sludge retention time (SRT) have commonly been adopted under a limiting dissolved oxygen (DO) condition (Modin et al, 2016;Rahman et al, 2014). The biosludge from the HRAS process, which is known as adsorptive sludge or young sludge, is more digestible than the waste activated sludge (WAS) produced from the CAS process.…”

Effects of Attached and Suspended Biomass on the Dynamics of the Microbial Community and Wastewater Characteristics in Sewers

“…However, these features also apply to specific, but not rare conditions or environments, in conventional sewers considering that sediments and the sewer wall, can serve as attached media [43] and that fluctuations in flow levels and organic loads are inevitable, even in separated sewers. Although it has been recognized that the sequential removal and oxidation of organic matter, especially nonoxidative removal, can serve as aerobic wastewater treatment [44], very few studies have focused on this mechanism in sewers. However, it was assumed that a very high yield value (0.79 g-biomass/g-acetate, corresponding to over ca.…”

Comparison of the Results from Microscopic Tests Concerning the Quality of Activated Sludge and Effluent

“…Edward Arden and William T. Lockett, members of the River Committee of the Manchester Corporation, UK, modified the research. Subsequently, they coined the term "activated sludge" and introduced it to the literature [1].…”

“…Activated sludge is a suspension of flocs in which bacterial cells are crucial active ingredients [1]. Sludge flocs consist of living and dead microorganisms such as bacteria (including filamentous bacteria), protozoa (ciliates, flagellates, amoebae), metazoa (rotifers, nematodes), fungi, and Actinobacteria.…”