Showing papers on "Enhanced biological phosphorus removal published in 1987"

Effect of phosphorus accumulation on acetate metabolism in the biological phosphorus removal process

Abstract: An experimental study was carried out to investigate the metabolic pathway of acetic acid and the relationship between the phosphorus accumulation in the sludge and the metabolism of organic substrates in the anaerobic aerobic biological phosphorus removal process. Two laboratory-scale anaerobic aerobic processes were operated continuously with different phosphorus loadings and batch experiments were conducted with the sludges obtained from the continuous systems. The metabolic pathway of acetate was postulated, in which NADH2 required for PHB synthesis is supplied from the consumption of intracellular carbohydrate through the EMP pathway. The ability of the sludge to uptake acetate anaerobically was limited by the amount of polyphosphate stored in the cell, so long as the phosphorus content of sludge was below 35 mgP/gVSS. From energy balance consideration, the energy required for the accumulation of polyphosphate is found to be very little compared with the total energy produced and the sludge can maintain the yield coefficient at a required level even when a large amount of polyphosphate is accumulated.

Phosphate release and uptake in enhanced biological phosphorus removal from wastewater

Abstract: Phosphorus removal from municipal and industrial waste waters is required to protect receiving waters from eutrophication (nutrient enrichment). Many treatment plants have been de signed or upgraded to uptake phosphorus, most often by the addition of chemicals. As an alternative, an enhanced biological phosphorus (bio-P) removal process offers the advantage of not requiring chemical additions and of reducing the volumes of sludge produced. A simple bio-P removal process must include at least two stages: non-aerated and aerated. In the first stage, influent wastewater and return sludge are combined under non aerated conditions. Phosphate release from the biomass and sol uble chemical oxygen demand (COD) removal are observed un der these anaerobic conditions in the absence of both oxygen and nitrate. In the subsequent aerated stage, phosphate removal from solution, COD removal and nitrification take place. Phos phorus-rich sludge is usually wasted from this aerobic reactor. Many processes also include an intermediate denitrification stage (often referred to as "anoxic") in which nitrified mixed liquor is recycled from the aerated reactor.

The phenomenon of simultaneous phosphate uptake and release, and its importance in biological nutrient removal

Abstract: The response of activated sludge following exposure to acetate is described. Batch systems were used to study phosphate release, phosphate accumulation and substrate utilization when sludge with known capability of excess phosphate removal was brought into contact with acetate under both aerobic and anoxic conditions. It is shown that acetate-induced phosphate release is not limited to anaerobic sludge but occurs equally readily in anoxic and aerobic environments, where it takes place concurrently with phosphate uptake. As a result of this phenomenon the amount of volatile fatty acids introduced into phosphate removing plants should not exceed the demand in the anaerobic stage. Also, phosphate accumulating sludge should not be used to estimate the readily biodegradable components of wastewater in anoxic or aerobic batch tests. Finally, the incorporation of excessive amounts of acetate in pure culture media designed to support enhanced phosphate uptake is counter productive and may in fact foster chemical precipitation.

Biochemistry and energetics of biological phosphorus removal

Abstract: A biochemical pathway which couples anaerobic uptake and storage of organic substrates with the depolymerlzation of polyphosphate and phosphate uptake to the aerobic metabolism of the stored organics has been proposed. The key feature of this pathway is the polyphosphate kinase enzyme which catalyzes both the anaerobic generation of ATP from polyphosphate and the aerobic replenishment of stored polyphosphate. Since the kinetic constants of this enzyme favor ATP formation, high metabolic activities are necessary to maintain the reverse reaction. This is supported by the effect of organic loading on enhanced biological phosphate uptake. Examination of the energetics of wastewater treatment shows that nitrate is only two-thirds as efficient as oxygen as an electron receptor. Because of this reduced efficiency, It is more difficult to reverse the reaction catalyzed by the polyphosphate kinase enzyme and Initiate anoxic phosphate uptake. Anoxic phosphate uptake has been shown to be feasible at high denitrification rates. Since denitrification rates Increase with Increasing organic loads, overall nutrient removal will be optimized by operating at the highest rate that will permit complete ammonia oxidation.

Comparison of biological and chemical phosphorus removals in continuous and sequencing batch reactors

Abstract: A full-scale study of phosphorus removal has been conducted at Culver using continuous-flow operation, SBR operation, and several different chemical treatment schemes. A full-scale demonstration of SBR biological phosphorus removal also has been shown to be effective. Four contributing groups of organisms and their roles in biological SBR phosphorus removal have been described: denitrifying organisms, fermentation product-manufacturing organisms, phosphorus- accumulating organisms, and aerobic autotrophs and heterotrophs. The SBR can provide the proper balance of anoxic, anaerobic, and aerobic conditions to allow these group of organisms to successfully remove phosphorus biologically, without chemical addition. Treatment results using various chemicals for phosphorus removal, both during conventional, continuous-flow operation and after the plant was converted for SBR operation, have also been provided for comparison. Effluent phosphorus concentrations were almost identical for each period, except for the period when phosphorus was removed biologically and without any chemical addition when effluent phosphorus concentrations were the lowest. These removals were made as a result of settling alone; no tertiary rapid stand filter was used or required.

Influence of return flow phosphorus load on performance of the biological phosphorus removal process

Abstract: The influence of the phosphorus load of the return flow on the performance of the biological phosphorus removal process as well as the behavior of the phosphorus in the sludge treatment process were investigated using a full-scale plant. With anaerobic digestion, about 60% of the phosphorus removed in the wastewater treatment process was again released in the sludge treatment process. When gravity-thickened sludge was directly dewatered without anaerobic digestion, an amount of phosphorus equal to the amount of phosphorus removed could be discharged from the process in the form of dewatered sludge cake. In order to obtain a mean effluent T-P concentration below 0.5 mg/l, phosphorus load of the return flow should be reduced. Possible countermeasures for preventing the release of phosphorus in the sludge treatment process were tested and the addition of Al coagulant to the sludge before gravity thickening proved to be effective.

Factors affecting biological phosphorus removal for the vip process, a high-rate university of capetown type process

Abstract: The phosphorus removal capabilities of the Virginia Initiative Plant (VIP) process, a high-rate biological nutrient removal (BNR) process, are presented and compared to the high-rate A2/0 and the low-rate University of Capetown (UCT) processes. The results indicate superior phosphorus removal capability for the VIP process compared to the A2/0 and UCT processes. In general, VIP process phosphorus removal was maximized by operation at the lowest possible total process mean cell residence time (MCRT) and with an aerobic hydraulic residence time (HRT) not exceeding 4 hours. A total process MCRT of 5 days provided acceptable nitrogen removal and excellent phosphorus removal for wastewater temperatures of 20°C or above, while a total process MCRT of 20 days would be required at a temperature of 12°C. Operation of the VIP process at an aerobic HRT greater than 4 hours apparently resulted in oxidation of stored organic matter that adversely affected phosphorus uptake kinetics. Data analysis suggested that the VIP process could have been operated at an anaerobic HRT as short as 20 minutes. Superior phosphorus removal performance was observed for the VIP process compared to the A2/0 process when the BOD5/TPO4 ratio of the wastewater was significantly less than 20.

A novel operational mode for a primary sludge fermenter for use with the enhanced biological phosphorus removal process

Abstract: This paper describes a simple operational mode for a primary sludge clarifier and fermenter system to be used in conjunction with the enhanced biological phosphorus (P) removal process. Preliminary experimental results show that the incorporation of this system into the design of a pilot-scale UCT process improved the P removal characteristics of the process by approximately 60% over those of a similar process receiving raw sewage, and resulted in average P removals in excess of 90% from organically weak (median COD = 181 mg/L) domestic wastewater without chemical addition over a six-month period.

The utilisation of polyphosphate as an energy reserve in Acinetobacter sp. and activated sludge.

Abstract: Acinetobacter , the most important contributor to enhanced biological phosphorus removal from wastewater, was isolated from activated sludge. The pure cultures took up and released phosphate just like activated sludge. Enzymes that play a role in the degradation of polyphosphate in microorganisms were studied, using cell-free extracts of Acinetobacter sp. Present were the enzymes polyphosphatase (activity: 20 nmol.min−1.mg−1 protein) and polyphosphate: AMP phosphotransferase (activity: 43 nmol.min−1.mg−1 protein). Not detected were: polyphosphate kinase, polyphosphate glucokinase and polyphosphate dependent NAD-kinase. Also present was the enzyme adenylate kinase (activity: 54 nmol.min−1.mg−1 protein). By the combined action of polyphosphate:AMP phosphotransferase and adenylate kinase Acinetobacter was able to regenerate ATP during the degradation of polyphosphate. Bacterial and synthetical polyphosphate (Graham's salt) could act as substrates for polyphosphate:AMP phosphotransferase. A low cost and quick assay was developed to measure the activity of this enzyme. From experiments with cell-free extracts of different types of activated sludge a correlation appeared between polyphosphate: AMP phosphotransferase activity and biological phosphate removal.

Phosphate removal by adsorption to activated carbon.

Abstract: The concentrations of phosphorus, nitrogen, and other nutritive elements in lakes, bays and inland seas are increased because domestic waste water, the second-step treated water from sewage treatment facilities, and the industrial waste water from some plants flow continuously into them. As a result, the waters are eutrophicated and the water quality is lowered, which results in unpalatable drinking water, red lakes, and various other problems. In typical cases, phosphorus acts as an accelerating substance for the growth of algae. Furthermore, phosphorus concentration is used as an indicator of the degree of eutrophication.Either or both of the nutritive elements, i.e., phosphorus and nitrogen, should be removed to prevent this eutrophication. It is difficult to remove nitrogen to a sufficiently low concentration by the ammonia stripping process or the activated sludge process. Therefore, prevention of eutriphication requires the effective removal of phosphorus.The methods for removing phosphorus include the chemical coagulation process, the adsorption process, the ion exchange process, the crystallization process, and the biological dephosphorization process. The coagulation process, which is most widely used, has problems as a result of the cost of chemical injection and the profuse generation of sludge. In the crystallization process and the biological dephosphorization process, on the other hand, there are many technical problems to be solved.Though recently an activated carbon adsorption process is often incorporated in the second-or the third-step liquid-waste treatment, there are very few studies on phosphate adsorption to activated carbon. This may be because activated carbon has been reported to be unsuitable for the adsorption of inorganic ions or lower alcohols. However, now that this process is utilized in practice, it is necessary to obtain detailed data on the properties of phosphate adsorption onto activated carbon.Basic studies on the adsorption treatment of phosphate-containing waste water have been carried out using adsorbents other than activated carbon, such as synthetic aluminium silicate, hydroxyapatite, and ion-exchange resin. These studies have shown that the adsorption of phosphate to such adsorbents proceeds through a chemical adsorption mechanisms.In the present study, the adsorption equilibrium and the adsorption rate of phosphate to activated carbon are examined to obtain basic data on the adsorption-removal treatment of phosphate-containing waste water by activated carbon. The phosphate concentrations were adjusted within the range of those in the first-or the second-step treated water. The adsorbates used are H3PO4, NaH2PO4, KH2PO4, and H6P4O13, which have been reported to be contained in these types of treated water.In addition, the relationships of the pore size distribution of activated carbon to the amount of adsorbate adsorbed and the intraparticle diffusivity are clarified.

Phostrip® process — a viable answer to eutrophication of lakes and coastal sea waters in italy

Abstract: The role of wastewater nutrients in eutrophication was recognized in the 1940's. Until the mid-1970's, the only means for removing wastewater phosphate, the nutrient generally thought to offer the best control measure, was chemical precipitation. The successful, full-scale demonstration at Seneca Falls, NY, introduced the cost-effective alternative of biological phosphorus removal. The method, called the PhoStrip process, causes the microorganisms in activated sludge to bioaccumulate and secrete phosphate. Biological phosphorus removal has since evolved into two types: “sidestream” (PhoStrip), and “fullstream” processes. PhoStrip systems have fully demonstrated their capability for sustained production of effluents averaging 1.0 mg/L, or less, total P, the effluent standard generally enforced. In addition to this unique achievement, PhoStrip systems provide overall plant operations advantages including compatability with any mode of activated sludge treatment, equal effectiveness over a wide range of F/M and P/BOD, sludge volume reduction, and protection against hydraulic surcharge and toxic shock. Tabularized official data from municipal PhoStrip II process, which reduces tankage volume, is described. Actual cost data from PhoStrip installations show major savings. Cost data are projected for the new PhoStrip II process. Thirteen references are cited.

Ecological selection of phosphorus-accumulating bacteria in sequencing batch reactor activated sludge processes for simultaneous removal of phosphorus, nitrogen and organic substances

Abstract: Laboratory-scale sequencing batch reactor (SBR) activated sludge processes were operated to clarify the behavior of microorganisms responsible for phosphorus removal during operation of the SBR and to demonstrate the related performance for simultaneous removal of nitrogen, phosphorus and BOD under modified operational schedule of the conventional SBR process The best performance for phosphorus removal was noted in operations where anoxic/anaerobic reactions were introduced into the fill period Remarkable release of phosphate from the solid into water phase (supernatant of mixed liquor) during the fill was followed by the luxury uptake of phosphate under aeration On the contrary, little phosphorus was removed in conventional operations in which aeration continued throughout a cycle Change from the operation with anoxic/anaerobic reaction during the fill to that with aerobic reaction throughout a cycle immediately decreased the activity of phosphorus removal Operation with anaerobic reaction, however, was not sufficient condition to remove phosphorus and, in addition, ecological selection and/or enrichment of the phosphorus accumulating bacteria were also necessary to remove phosphorus under operation with anaerobic condition

Factors affecting anaerobic stabilization during biological phosphorus removal

Abstract: Laboratory and pilot-plant scale research was conducted to Investigate the occurrence of COD stabilization in the anaerobic reactor of biological phosphorus removal systems. Initial efforts in the laboratory established the existence of anaerobic stabilization. Subsequent efforts investigated the effects of influent substrate, sludge age, and other operating conditions on the extent of anaerobic stabilization, in an effort to establish the primary mechanism responsible for such stabilization. It was determined that sludge age does effect anaerobic stabilization but the composition of the influent substrate is the primary factor that determines its extent. It was concluded that the normal growth of fermenting bacteria is the principal mechanism of anaerobic stabilization.

Introduction of biological phosphorus removal to an activated sludge plant with practical limitations

Abstract: Biological P-removal has been introduced in a full-scale plant. Pilot plant and laboratory studies were carried out simultaneously. At low sludge loadings the P-removal at the full-scale plant increased to 55% against 16% under conventional conditions. However the degree of nitrification decreased. A higher P-removal was achieved by using unsettled influent and during an accumulation of sludge in the primary clarifiers. A poor P-removal of 23% was the result of recirculating effluent. In the pilot plant the use of an extended anaerobic zone and the use of step loading had no positive effect. During these studies there was probably a deficiency of lower fatty acids and the influence of nitrate on the P-removal was high. The composition of the influent (COD:N:P) was unfavourable for a complete P-removal. The system was sensitive to the development of bulking sludge. In the full-scale plant the main cause was a disturbance of the plug flow by underwater mixers in the anaerobic zone. The use of a contact tank gave positive results.

A kinetic model for biological phosphorus removal incorporating intracellular organics and phosphorus pools

Abstract: A series of studies on kinetics of biological phosphorus removal were conducted. A kinetic model of the biological phosphorus removal process, which is intended for future use for the purposes of evaluating performance of the process and the operational conditions, was developed based upon the experimental results and is described in this paper. The model was developed taking into account phosphorus release and ingestion, TOC removal, and an intracellular organic substrate metabolism. Values of the constants and coefficients for the model were estimated from the experimental data. It was shown that the proposed model could simulate the phenomena of phosphorus release and removal, TOC removal as well as changes in intracellular carbohydrate and PHB contents.

Biological nutrient removal in anoxic‐anaerobic‐aerobic treatment process

Abstract: A suspended growth biological nutrient removal process was designed and operated to achieve high removal of organics, nitrogen and phosphorus from wastewater without the addition of chemicals. The process utilized anoxic, anaerobic and aerobic reactor sequences with sludge return. A bench‐scale unit was operated in the laboratory. The biological kinetic coefficients for removal of BOD5 were developed by varying the mean cell residence time. This was achieved by operating the reactors at six different MLSS concentrations, 5000, 4200, 3300, 2600, 1900, and 1200 mg/L. This process eliminated the need for an internal recycle; and total detention time for three reactors was less than that for conventional activated sludge.

Carbon flow and effluent variability in phosphorus-accumulating activated sludge cultures

Abstract: Effluent phosphorus variability from bench-scale activated sludge systems operated for biological phosphorus removal was correlated with the loading history of the sludge culture. Same-day loading rates could not be used to adequately describe/predict system phosphorus removal. Intermittent carbon supplementation was used to maintain long-term average total phosphorus levels below 1.0 mg/L. The frequency and magnitude of carbon supplementation was estimated using a three day weighted moving average of the organic loading rate. Batch studies using 14C labelled substrates verified that acetate would be an effective source of organic material for carbon supplementation and effluent quality enhancement. While other organic materials may be satisfactory sources of carbon, the use of acetate ensures that the greatest percentage of added carbon will be sequestered by the target microbial species.

Effect of variable influent loading on biological phosphorus removal

Abstract: Biological phosphorus (bio‐P) removal processes are receiving increased attention as the costs and sludge disposal problems associated with traditional metal precipitation become of greater concern to system designers and operators. Biological processes, however, have not demonstrated the same ability as chemical processes to consistently produce effluents low in total phosphorus. The results of this investigation indicate that the dynamic biochemical oxygen demand (BOD) and phosphorus loading patterns observed at full‐scale systems can impose varying degrees of stress on bio‐P removal processes. Increases in the amount of loading‐related stress on bench‐scale bio‐P systems are manifested by increases in long‐term average effluent phosphorus concentrations. Effluent variability is magnified when activated sludge systems are operated for both nitrogen and phosphorus removal. Mitigating measures can be employed to improve long‐term process performance, but at the cost of increased system complexity and incr...

Biological phosphorus removal at an experimental full-scale plant in France

Abstract: In France, all phosphorus removal treatment has been based on precipitation by means of chemical reagents. With a view to reducing costs, a series of laboratory experiments was initiated and subsequently followed up by full-scale studies in early 1984 at the Saint-Mars-la-Jaille treatment plant. This is the first biological P-removal plant to be put on line in France.The plant operates at low loading levels with extended aeration. Nitrification–denitrification is achieved in controlled aerobic and nonaerobic zones through a multi-mini-step process in a plug–flow reactor. Complete nitrate removal results in a release of phosphorus during the anaerobic phase and, hence in a high level of phosphorus accumulation in the aerobic sludge.Phosphorus removal was optimized by replacing the thickener with a new flotation thickener to minimize P-release in the anaerobic sludge blanket. The phosphorus removal levels obtained varied from 35% at the outset of the study to 89% upon stabilization. This paper outlines the ...

Biological phosphate removal from wastewaters : proceedings of an IAWPRC Specialized Conference held in Rome, Italy, 28-30 September, 1987

Abstract: Selected papers. Utilization of polyphosphate as an energy reserve in Acinetobacter sp. and activated sludge, J W van Groenestijn & M H Deine a. Metabolic control in polyphosphate - accumulating bacteria and its role in enhanced biological phosphate removal, L H Lotter & I A Duber . Biochemistry and energetics of biological phosphorus removal, K D Tracy & A Flammin . Simultaneous control of biological phosphorus removal and sludge settleability, P A Wilderer & J Dettmer Experiments towards establishing the kinetics of biological excess phosphorus removal, M C Wentzel et al . Effect of anaerobic zone on settleability of activated sludge, J Wanner et al . Biological phosphorus removal with and without side-stream precipitation, R Schonberger. Stepped supply process for simultaneous biological removal of nitrogen and phosphorus from wastewater, F Bourdon et al . Influence of return flow phosphorus load on performance of the biological phosphorus removal process, T Murakami et al . Biological removal of phosphates from wastewaters: full-scale experience and operational results with the Phostrip process, G V Levin et al. Improvement to the stability of the biological phosphate removal process at the Johannesburg Northern Works, H A Nicholls et al. Acinetobacter sp. growth in alternate anaerobic-aerobic conditions, V Tandoi et al . Biological phosphorus removal under defined conditions in a fill-and-draw system, K J Appeldoorn & M H Deine a. The influence of low temperature on biological phosphorus removal at Kelowna, Canada, T D Vassos.

The influence of low temperature on biological phosphorus removal at kelowna, canada

Abstract: Four years of monitoring data obtained from a biological nutrient removal treatment plant operating at Kelowna, British Columbia, are examined with respect to temperature effects on phosphorus removal. The plant exhibits a dual mode of operation with respect to temperature; the boundary of which occurs at approximately 15°C. Overall phosphorus removals of approximately 68% are achieved at liquid temperatures at or below 15°C, and removals of 85% are achieved at liquid temperatures above 15°C. There is an indication that phosphorus release and uptake in specific reactor zones may be adversely affected by denitrification in specific reactor zones at liquid temperatures above 15°C.

Study of the reduction of returned phosphorus from a sludge treatment process

Abstract: Pilot plant experiments on biological phosphorus removal from municipal wastewater, sludge thickening and dewatering, were performed to investigate the quantity of released phosphorus from a sludge treatment process and a system for minimizing this phosphorus. A combination process of biological phosphorus removal with chemical phosphorus removal was very effective, not only for reducing the phosphorus but also for steadily removing phosphorus when the T-P/BOD ratio of the wastewater was over 0.08. An intermediate clarifier and fluidized phosphorus crystallization reactor were operated as a chemical phosphorus removal process, the soluble PO4-P removal was 80% and the packed phosphorus rocks were enlarged to twice the size of the initially packed rocks after one month of operation. From experimental results, it was clear that separate thickening of primary sludge and excess activated sludge was effective in reducing the quantity of phosphorus returning to the biological process. Precipitation removal of phosphorus from the filtrate of a sludge dewatering process, using a chemical precipitant, was also effective in reducing the returning phosphorus. When the excess activated sludge is dewatered alone, aerating the thickened sludge can be adopted effectively.