Showing papers on "Enhanced biological phosphorus removal published in 2014"

Migration of Phosphorus in Sewage Sludge during Different Thermal Treatment Processes

Abstract: The utilization of phosphorus (P) in activated sludge discharged from wastewater treatment plants is an important part of the global phosphorus circulation. Thermal treatment of excess sludge would become a promising method for their disposal throughout the world. Herein, we investigated the transformation and migration of P in sewage sludge during different thermal treatment conditions. The results indicate that the temperature can significantly influence the species and content of P in the sewage sludge char or ash (SSC/A), while the atmosphere of thermal treatment has a slight effect on the fate of P. 31P NMR and XRD analysis indicated that P migrated mainly to the medium-term plant available P pool (poolNaOH) on treating the sewage sludge at a low temperature (673–873 K), while it was prone to migration to the long-term plant available P pool (poolHCl) when treated at a high temperature (873–1073 K).

Improving Phosphorus Availability in an Acid Soil Using Organic Amendments Produced from Agroindustrial Wastes

Abstract: In acid soils, soluble inorganic phosphorus is fixed by aluminium and iron. To overcome this problem, acid soils are limed to fix aluminium and iron but this practice is not economical. The practice is also not environmentally friendly. This study was conducted to improve phosphorus availability using organic amendments (biochar and compost produced from chicken litter and pineapple leaves, resp.) to fix aluminium and iron instead of phosphorus. Amending soil with biochar or compost or a mixture of biochar and compost increased total phosphorus, available phosphorus, inorganic phosphorus fractions (soluble inorganic phosphorus, aluminium bound inorganic phosphorus, iron bound inorganic phosphorus, redundant soluble inorganic phosphorus, and calcium bound phosphorus), and organic phosphorus. This was possible because the organic amendments increased soil pH and reduced exchangeable acidity, exchangeable aluminium, and exchangeable iron. The findings suggest that the organic amendments altered soil chemical properties in a way that enhanced the availability of phosphorus in this study. The amendments effectively fixed aluminium and iron instead of phosphorus, thus rendering phosphorus available by keeping the inorganic phosphorus in a bioavailable labile phosphorus pool for a longer period compared with application of Triple Superphosphate without organic amendments.

Luxury uptake of phosphorus by microalgae in waste stabilisation ponds: current understanding and future direction

Abstract: There is a need to improve phosphorus removal for the tens of thousands of small communities around the world that currently rely on waste stabilisation ponds for their wastewater treatment. We now know that microalgae in pond systems are capable of accumulating phosphorus within their cells as polyphosphate in a process known as luxury uptake, but this knowledge has not yet been applied to engineer a new process to improve phosphorus removal. This paper summarises the current understanding of this mechanism, discusses the key factors influencing polyphosphate accumulation and provides future direction for research in this field. There have only been a limited number of studies that have focussed on luxury uptake of polyphosphate by microalgae in high phosphorus concentration environments such as those found in waste stabilisation pond systems. However, from this review it has been shown that the environmental factors which influence polyphosphate storage are the phosphate concentration, light intensity and temperature. Currently we are limited to a black box understanding of the bulk population and as a result future research needs to focus on a systematic evaluation of different microalgal genera under a wide range of environmental, biological and process variables in order to reveal the conditions needed to reliably trigger this phenomenon. This will then provide the basis for developing a new algal biotechnology optimised for luxury uptake of polyphosphate. While there are still several key questions that need to be answered there is potential for this to lead to a process which could be as significant to pond systems as the development of enhanced biological phosphorus removal was for the activated sludge process.

A Comprehensive Review of Phosphorus Removal Technologies and Processes

Abstract: Phosphorus removal from polluted water is a global concern considering the detrimental environmental effects that excess phosphorus has. Phosphorus can lead to poor water quality and aquatic life loss due to eutrophication when found in excess in aquatic systems. Industry and agriculture are two of the main sources that lead to the accumulation of phosphorus in wastewater. In an attempt to prevent harmful environmental effects of excess phosphorus, several techniques have been designed to remove phosphorus from wastewater. These techniques range from adsorption and precipitation to enhanced biological phosphorus removal and constructed wetlands. Adsorption and precipitation predominantly require the use of different metals in the phosphorus removal process. This article reviews the results found in the last nine years pertaining to phosphorus removal through the use of adsorption and precipitation using different metal-containing compounds. Advances concerning the parameters of enhanced biological phospho...

The impact of titanium dioxide nanoparticles on biological nitrogen removal from wastewater and bacterial community shifts in activated sludge

Abstract: The potential impact of titanium dioxide nanoparticles (TiO2 NPs) on nitrogen removal from wastewater in activated sludge was investigated using a sequencing batch reactor. The addition of 2–50 mg L−1 of TiO2 NPs did not adversely affect nitrogen removal. However, when the activated sludge was exposed to 100–200 mg L−1 of TiO2 NPs, the effluent total nitrogen removal efficiencies were 36.5 % and 20.3 %, respectively, which are markedly lower than the values observed in the control test (80 %). Further studies showed that the decrease in biological nitrogen removal induced by higher concentrations of TiO2 NPs was due to an inhibitory effect on the de-nitrification process. Denaturing gradient gel electrophoresis profiles showed that 200 mg L−1 of TiO2 NPs significantly reduced microbial diversity in the activated sludge. The effect of light on the antibacterial activity of TiO2 NPs was also investigated, and the results showed that the levels of TiO2-dependent inhibition of biological nitrogen removal were similar under both dark and light conditions. Additional studies revealed that different TiO2 concentrations had a significant effect on dehydrogenase activity, and this effect was most likely the result of decreased microbial activity.

Biological nutrients removal from the supernatant originating from the anaerobic digestion of the organic fraction of municipal solid waste

Abstract: This study critically evaluates the biological processes and techniques applied to remove nitrogen and phosphorus from the anaerobic supernatant produced from the treatment of the organic fraction of municipal solid waste (OFMSW) and from its co-digestion with other biodegradable organic waste (BOW) streams. The wide application of anaerobic digestion for the treatment of several organic waste streams results in the production of high quantities of anaerobic effluents. Such effluents are characterized by high nutrient content, because organic and particulate nitrogen and phosphorus are hydrolyzed in the anaerobic digestion process. Consequently, adequate post-treatment is required in order to comply with the existing land application and discharge legislation in the European Union countries. This may include physicochemical and biological processes, with the latter being more advantageous due to their lower cost. Nitrogen removal is accomplished through the conventional nitrification/denitrification, nitritation/denitritation and the complete autotrophic nitrogen removal process; the latter is accomplished by nitritation coupled with the anoxic ammonium oxidation process. As anaerobic digestion effluents are characterized by low COD/TKN ratio, conventional denitrification/nitrification is not an attractive option; short-cut nitrogen removal processes are more promising. Both suspended and attached growth processes have been employed to treat the anaerobic supernatant. Specifically, the sequencing batch reactor, the membrane bioreactor, the conventional activated sludge and the moving bed biofilm reactor processes have been investigated. Physicochemical phosphorus removal via struvite precipitation has been extensively examined. Enhanced biological phosphorus removal from the anaerobic supernatant can take place through the sequencing anaerobic/aerobic process. More recently, denitrifying phosphorus removal via nitrite or nitrate has been explored. The removal of phosphorus from the anaerobic supernatant of OFMSW is an interesting research topic that has not yet been explored. At the moment, standardization in the design of facilities that treat anaerobic supernatant produced from the treatment of OFMSW is still under development. To move toward this direction, it is first necessary to assess the performance of alternative treatment options. It study concentrates existing data regarding the characteristics of the anaerobic supernatant produced from the treatment of OFMSW and from their co-digestion with other BOW. This provides data documenting the effect of the anaerobic digestion operating conditions on the supernatant quality and critically evaluates alternative options for the post-treatment of the liquid fraction produced from the anaerobic digestion process.

Microbial and metabolic characterization of a denitrifying phosphorus-uptake/side stream phosphorus removal system for treating domestic sewage

Abstract: In this study, an advanced wastewater treatment process, the denitrifying phosphorus/side stream phosphorus removal system (DPR-Phostrip), was developed for the purpose of enhancing denitrifying phosphorus removal. The enrichment of denitrifying phosphorus-accumulating organisms (DPAOs) and the microbial community structure of DPR-Phostrip were evaluated by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), and the metabolic activity of seed sludge and activated sludge collected after 55 days of operation were evaluated by Biolog™ analysis. This experimental study of DPR-Phostrip operation showed that nutrients were removed effectively, and denitrifying phosphorus removal was observed during the pre-anoxic period. PCR-DGGE analysis indicated that DPR-Phostrip supported DPAO growth while inhibiting PAOs and GAOs. The major dominant species in DPR-Phostrip were Bacteroidetes bacterium, Saprospiraceae bacterium, and Chloroflexi bacterium. Moreover, the functional diversity indices calculated on the basis of Biolog analysis indicated that DPR-Phostrip had almost no effect on microbial community diversity but was associated with a shift in the dominant species, which confirms the results of the PCR-DGGE analysis. The results for average well color development, calculated via Biolog analysis, showed that DPR-Phostrip had a little impact on the metabolic activity of sludge. Further principal component analysis suggested that the ability to utilize low-molecular-weight organic compounds was reduced in DPR-Phostrip.

Impact of salinity on the anaerobic metabolism of phosphate-accumulating organisms (PAO) and glycogen-accumulating organisms (GAO)

Abstract: The use of saline water as secondary quality water in urban environments for sanitation is a promising alternative towards mitigating fresh water scarcity. However, this alternative will increase the salinity in the wastewater generated that may affect the biological wastewater treatment processes, such as biological phosphorus removal. In addition to the production of saline wastewater by the direct use of saline water in urban environments, saline wastewater is also generated by some industries. Intrusion of saline water into the sewers is another source of salinity entering the wastewater treatment plant. In this study, the short-term effects of salinity on the anaerobic metabolism of phosphate-accumulating organisms (PAO) and glycogen-accumulating organisms (GAO) were investigated to assess the impact of salinity on enhanced biological phosphorus removal. Hereto, PAO and GAO cultures enriched at a relatively low salinity level (0.02 % W/V) were exposed to salinity concentrations of up to 6 % (as NaCl) in anaerobic batch tests. It was demonstrated that both PAO and GAO are affected by higher salinity levels, with PAO being the more sensitive organisms to the increasing salinity. The maximum acetate uptake rate of PAO decreased by 71 % when the salinity increased from 0 to 1 %, while that of GAO decreased by 41 % for the same salinity increase. Regarding the stoichiometry of PAO, a decrease in the P-release/HAc uptake ratio accompanied with an increase in the glycogen consumption/HAc uptake ratio was observed for PAO when the salinity increased from 0 to 2 % salinity, indicating a metabolic shift from a poly-P-dependent to a glycogen-dependent metabolism. The anaerobic maintenance requirements of PAO and GAO increased as the salinity concentrations risen up to 4 % salinity.

A Comparative Study of the Bacterial Community in Denitrifying and Traditional Enhanced Biological Phosphorus Removal Processes

Abstract: Denitrifying phosphorus removal is an attractive wastewater treatment process due to its reduced carbon source demand and sludge minimization potential. Two lab-scale sequencing batch reactors (SBRs) were operated in alternating anaerobic-anoxic (A-A) or anaerobic-oxic (A-O) conditions to achieve denitrifying enhanced biological phosphate removal (EBPR) and traditional EBPR. No significant differences were observed in phosphorus removal efficiencies between A-A SBR and A-O SBR, with phosphorus removal rates being 87.9% and 89.0% respectively. The community structures in denitrifying and traditional EBPR processes were evaluated by high-throughput sequencing of the PCR-amplified partial 16S rRNA genes from each sludge. The results obtained showed that the bacterial community was more diverse in A-O sludge than in A-A sludge. Taxonomy and β-diversity analyses indicated that a significant shift occurred in the dominant microbial community in A-A sludge compared with the seed sludge during the whole acclimation phase, while a slight fluctuation was observed in the abundance of the major taxonomies in A-O sludge. One Dechloromonas-related OTU outside the 4 known Candidatus “Accumulibacter” clades was detected as the main OTU in A-A sludge at the stationary operation, while Candidatus “Accumulibacter” dominated in A-O sludge.

Metagenomic characterization of 'Candidatus Defluviicoccus tetraformis strain TFO71', a tetrad-forming organism, predominant in an anaerobic-aerobic membrane bioreactor with deteriorated biological phosphorus removal.

Abstract: Summary In an acetate-fed anaerobic–aerobic membrane bioreactor with deteriorated enhanced biological phosphorus removal (EBPR), Defluviicoccus-related tetrad-forming organisms (DTFO) were observed to predominate in the microbial community Using metagenomics, a partial genome of the predominant DTFO, ‘Candidatus Defluviicoccus tetraformis strain TFO71’, was successfully constructed and characterized Examining the genome confirmed the presence of genes related to the synthesis and degradation of glycogen and polyhydroxyalkanoate (PHA), which function as energy and carbon storage compounds TFO71 and ‘Candidatus Accumulibacter phosphatis’ (CAP) UW-1 and CAP UW-2, representative polyphosphate-accumulating organisms (PAO), have PHA metabolism-related genes with high homology, but TFO71 has unique genes for PHA synthesis, gene regulation and granule management We further discovered genes encoding DTFO polyphosphate (polyP) synthesis, suggesting that TFO71 may synthesize polyP under untested conditions However, TFO71 may not activate these genes under EBPR conditions because the retrieved genome does not contain all inorganic phosphate transporters that are characteristic of PAOs (CAP UW-1, CAP UW-2, Microlunatus phosphovorus NM-1 and Tetrasphaera species) As a first step in characterizing EBPR-associated DTFO metabolism, this study identifies important differences between DTFO and PAO that may contribute to EBPR community competition and deterioration

The effects of carbon nanotubes on nitrogen and phosphorus removal from real wastewater in the activated sludge system

Abstract: The wide use of carbon nanotubes (CNTs), such as single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), inevitably causes their release into the environment. Previous studies pointed out that the released CNTs would have negative effects on model animals, plants, or microorganisms. Nevertheless, to date, it is unclear whether the presence of CNTs in wastewater treatment plants (WWTPs) could affect biological nitrogen and phosphorus removal. In this paper, the potential effects of CNTs (SWNTs and MWNTs) on nitrogen and phosphorus removal from real wastewater in an activated sludge system were investigated. It was found that the presence of CNTs had no significant impacts on nitrogen and phosphorus removal even at the exposure concentration of 100 mg L−1. Mechanism studies indicated that the sludge membrane integrity and viability and the respiration of both heterotrophic and autotrophic microorganisms were not affected by CNTs. Further experiments revealed that the presence of CNTs also did not change the transformations of intracellular metabolites (mainly glycogen and polyhydroxyalkanoates) and activities of key enzymes (mainly ammonia monooxygenase, nitrite oxidoreductase, nitrate reductase, nitrite reductase, exopolyphosphatase, and polyphosphate kinase), which was consistent with no observed influences on nitrogen and phosphorus removal.