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Wastewater Treatment: Biological
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Water Resources and Hydrological Systems, 2020
Shaikh Ziauddin Ahammad, David W. Graham, Jan Dolfing
The removal of phosphorus from the wastewater by the biological means is known as biological removal of phosphorus. The groups of microorganisms that are largely responsible for phosphorus removal are known as the polyphosphate-accumulating organisms (PAOs). These organisms are able to store phosphate as intracellular polyphosphate, leading to phosphorus removal from the bulk liquid phase through PAO cell removal in the waste activated sludge. Enhanced biological phosphorus removal can be achieved through the ASP by recirculating sludge through anaerobic and aerobic conditions.[50] Unlike most other microorganisms, PAOs can take up carbon sources such as VFAs under anaerobic conditions, and store them intracellularly as carbon polymers, namely poly-β-hydroxy-alkanoates (PHAs). The energy for this biotransformation is mainly generated by the cleavage of polyphosphate and release of phosphate from the cell. Reducing power is also required for PHA formation, which is produced largely through the glycolysis of internally stored glycogen.[51] The principal advantages of biological phosphorous removal are reduced chemical costs and less sludge production as compared with chemical precipitation.
Nutrients Removal and Recovery in Bioelectrochemical Systems
Published in Sonia M. Tiquia-Arashiro, Deepak Pant, Microbial Electrochemical Technologies, 2020
Addressing the phosphorus pollution is of great importance. Traditional phosphorus removal technologies include biological processes, chemical precipitation and membrane filtration, etc. In the enhanced biological phosphorus removal (EBPR), polyphosphate accumulating organisms (PAOs) are enriched through aerobic and anaerobic processes during which such special bacteria are capable of storing phosphate within their cells at a level higher than normal and then are removed as waste sludge. Chemical precipitation by adding precipitates, such as lime (Ca(OH)2), alum (Al2(SO4)3·18H2O) and ferric chloride (FeCl3), is considered as an easy and low cost way to remove phosphorus from wastewater (De-Bashan and Bashan 2004). Membrane filtration systems are applied to achieve phosphorus removal in the form of both dissolved and solid phosphorus, for instance, reverse osmosis (RO) systems and membrane bioreactors (MBRs) (Sengupta et al. 2015).
Outlook and main conclusions
Published in Francisco Javier Rubio Rincon, Effect of Sulphide on Enhanced Biological Phosphorus Removal, 2017
The increase of phosphorus in water bodies causes eutrophication which finally results in hypoxia. From the phosphorus generated by human activities, 70% is found in wastewater. Therefore, it is important to remove phosphorus from the treated effluent at wastewater treatment plants. Enhanced biological removal of phosphorus is a worldwide use process to remove phosphorous biologically. The biological phosphorus removal (BPR) is carried out by organisms capable to store phosphorus above their growth requirements. These organisms are known as polyphosphate accumulating organisms (PAOs).
Pilot-scale study for phosphorus recovery by sludge acidification and dewatering
Published in Environmental Technology, 2020
Cejna Anna Quist-Jensen, Lisbeth Wybrandt, Hanne Løkkegaard, Sebastian Buch Antonsen, Morten Lykkegaard Christensen
In this study, the aim is to enhance phosphorus recovery by acidification of sludge. Different phosphorus pools exist in sludge such as chemical bound phosphorus, organic bound phosphorus, and polyphosphate in polyphosphate-accumulating organisms (PAOs) if phosphorus is removed biologically. Acidification dissolves poorly soluble metal-phosphorus compounds [9–11]. Laboratory experiments have shown that more than 80% of the phosphorus can be dissolved by acidification depending on the sludge type [12,13]. Between 60 and 100 mmol ortho-phosphate has been released per added mole sulphuric acid added to the sludge when the method was tested in bench scale [13]. Phosphorus can be extracted from different types of sludge, e.g. undigested sludge (primary and/or secondary sludge) and digested sludge. The phosphor concentration is lower in undigested sludge, and less phosphorus can be released; however, the required amount of sulphuric acid is higher for digested sludge due to formation of carbonate during digestion [13]. Sludge from three wastewater treatment plants including both plants with digested and plants with non-digested sludge have therefore been selected for investigation of the potential for phosphorus recovery in a pilot scale set-up for acidification and separation of sludge.
Potential of suspended growth biological processes for mixed wastewater reclamation and reuse in agriculture: challenges and opportunities
Published in Environmental Technology Reviews, 2021
Precious N. Egbuikwem, Gregory C. Obiechefu, Faisal I. Hai, Ma. Catriona E. Devanadera, Devendra P. Saroj
Biological phosphorus removal (BPR) is undertaken by bacteria that accumulate phosphorus in excess of their normal metabolic requirements, and these bacteria are generally referred to as polyphosphate accumulating organisms (PAOs). Cycling of microbial biomass and influent wastewater between anaerobic and aerobic reactor zones allows for the proliferation of PAOs with the capacity to accumulate polyphosphates intracellularly in aerobic conditions [106]. Under anaerobic conditions, PAOs take up short chain volatile fatty acids (VFAs) like acetates and store them intracellularly as carbon polymer such as poly-B-hydroxybutyrates (PHAs) to be synthesized in aerobic conditions, and by cleavage of the stored polyphosphate the energy required for the biotransformation is generated and phosphate is released into the bulk liquor [106]. Under aerobic conditions, the PHA is metabolized to drive biomass growth and provide the energy required for uptake of all available orthophosphate and storage of polyphosphate, and excess phosphorus is removed from the bulk liquid by wasting polyphosphate-rich sludge [106,107]. Outside the anaerobic–aerobic operation that serves as the major pathway for the removal of phosphorus in enhanced biological phosphorus removal (EBPR), some PAOs are capable of utilizing nitrate or nitrite as electron acceptor instead of oxygen for uptake of phosphorus from the bulk liquid, thus allowing for simultaneous phosphorus removal and denitrification [108]. Like the nitrogen, phosphorus removal can be achieved in a single-stage reactor by providing the enabling environment for efficient operation of specialized microbial populations [106,108].