Enhanced Phosphorus Removal Research Articles

A modified BAF system configuring synergistic denitrification and chemical phosphorus precipitation: Examination on pollutants removal and clogging development

The performance of a BAF system configuring simultaneous chemical phosphorus precipitation in the pre-denitrification stage was examined using a continuously operated setup to treat real domestic wastewater. The effects of using no chemical, dosing sole Fe2+, and dosing combined Fe2+, PAM, and NaHCO3 in the pre-denitrification tank were assessed by monitoring COD, nitrogen, and phosphorus removal and hydraulic headloss development in the BAF column. Though dosing sole Fe2+ significantly enhanced phosphorus removal, it would consume alkalinity through hydrolysis and form smaller-sized sludge flocs in the pre-denitrification tank, and hence resulted in affected NH4+-N, insoluble COD, and SS removal in the BAF. Dosing combined Fe2+, PAM, and NaHCO3 can enhance sludge flocculation to form larger flocs and compensate alkalinity consumption. It exhibited sound performance on COD, nitrogen, and phosphorus removal, and led to less frequent BAF backwashing by slowing clogging development in the BAF filter layer.

Enhancing combined biological nitrogen and phosphorus removal from wastewater by applying mechanically disintegrated excess sludge

The goal of the study was to evaluate the possibility of applying disintegrated excess sludge as a source of organic carbon to enhance biological nitrogen and phosphorus removal. The experiment, performed in a sequencing batch reactor, consisted of two two-month series, without and with applying mechanically disintegrated excess sludge, respectively. The effects on carbon, nitrogen and phosphorus removal were observed. It was shown that the method allows enhancement of combined nitrogen and phosphorus removal. After using disintegrated sludge, denitrification effectiveness increased from 49.2 ± 6.8% to 76.2 ± 2.3%, which resulted in a decline in the NOx–N concentration in the effluent from the SBR by an average of 21.4 mg NOx–N/L. Effectiveness of biological phosphorus removal increased from 28.1 ± 11.3% to 96.2 ± 2.5%, thus resulting in a drop in the PO43−−P concentration in the effluent by, on average, 6.05 mg PO43−−P/L. The application of disintegrated sludge did not deteriorate effluent quality in terms of COD and NH4+−N. The concentration of NH4+−N in both series averaged 0.16 ± 0.11 mg NH4+−N/L, and the concentration of COD was 15.36 ± 3.54 mg O2/L.

Effect of a Humus Soil Side-Stream Reactor (HSR) on the Bacterial Characteristics in Enhanced Biological Phosphorus Removal Process

Three enhanced phosphorus removal processes, each with a sequencing batch reactor (SBR), one with a humus soil side-stream reactor, one with an anaerobic side-stream reactor, and one without a side stream reactor (used as a conventional SBR process), designated as HS-SBR, A-SBR, and C-SBR, respectively, were operated and compared for the treatment of municipal sewage in laboratory scale. Compared with the total phosphorus (TP) removal efficiency of 68.3% obtained in the C-SBR, the TP removal efficiency in the A-SBR was only 53.2%, while in the HS-SBR, it increased to 85.6%. This observation suggested that the anaerobic side-stream reactor repressed TP removal in the system, while the humus soil side-stream reactor improved the TP removal. The detailed biochemical microbial analysis showed that the anaerobic side-stream reactor inhibited the TP removal activity through the repression of the polyphosphate kinase activity in the A-SBR, while the humus soil side-stream reactor improved the TP removal through improving the growth of polyphosphate-accumulating organisms and the activity of polyphosphate kinase, and inhibiting the growth of glycogen accumulating organisms in the HS-SBR. It was further speculated that humus soil in the humus soil side-stream reactor influenced the metabolism of PAOs and GAOs in the SBR.

Impacts of poly-aluminum chloride addition on activated sludge and the treatment efficiency of SBR

Coagulants addition to a bioreactor is a widely used technology for improving phosphorus removal. As a common and low-cost coagulant, poly-aluminum chloride (PAC) may be widely used for wastewater treatment. In this article, the impacts of PAC on activated sludge and the treatment efficiency of sequencing batch reactor were investigated over 100 d for domestic wastewater treatment. Parameters of chemical oxygen demand (COD), nitrogen, phosphorus, MLSS, oxygen uptake rate (OUR), and dehydrogenase activity (DHA) were used to assess the activated sludge performance. The addition of 40 mg PAC/L (R2) enhanced phosphorus removal from 73.3% in control with zero PAC (R1) to 92.4% due to simultaneous chemical precipitation. PAC addition improved COD removal slightly and did not affect the removal efficiency of nitrogen. The average removal efficiency of COD of the reactor increased slightly from 86.2 to 89.6% by PAC addition. In R1, TN removal was in the range from 86.3 to 90.8%. Nitrogen removal efficiency remained unaffected (slightly dropped) during simultaneous precipitation in R2 and was in the range from 84.5 to 86.8%. The average inhibition rate of DHA and OUR was 32.1 and 55.3%, respectively. PAC addition gave proof to the increase of MLSS by some 40%. Results obtained from the present work confirmed that PAC addition, despite the toxicity and inhibition on micro-organisms, favored phosphorus removal in wastewater treatment.

Reusing industrial by-products to enhance phosphorus removal in waste stabilization ponds: laboratory approach

Waste stabilization ponds (WSP), in spite of being a suitable technology for wastewater treatment, present low phosphorus removal. This study aimed at evaluating the net increase on phosphorus removal efficiency in microcosm WSP in which sludge was conditioned with an adsorbent (industrial by-product) having a high phosphorus retention capacity. In order to determine the best candidate to condition the sludge, four different industrial by-products (granular bentonite; fly ashes from a municipal solid waste incineration plant; and two types of fly ashes from power plants) were tested for their phosphorus adsorption capacity. Experimental results were fitted to Langmuir and Freundlich models. All adsorbents showed a high phosphorus adsorption capacity. Maximum phosphorous adsorption capacity estimated from Langmuir equations ranged between 34.7 and 74.0 mgP/g adsorbent, being fly ashes from a power plant and granular bentonite the adsorbents with the highest and lowest adsorption capacity, respectively. Microcosms WSP were set up and the sludge conditioned with fly ashes from a municipal solid waste incineration plant. Results showed that phosphorus removal efficiency increased up to 90% by adding 5% of adsorbent (in terms of weight of adsorbent to weight of sludge). Main conclusion is that of industrial by-products may be a low-cost solution for enhancing phosphorus removal in WSP.

Landfill Leachate Nutrient Removal Using Intermittent Aeration

The aim of this study was to investigate the biological removal of nitrogen and phosphorus from an intermediate age leachate diluted with domestic wastewater. A sequencing batch reactor (SBR) with alternate aeration was operated under aerobic (Ox) and anoxic (Ax) phases of different durations (Ox 3 or 6 h and Ax 1, 2 or 3 h), for a total cycle period of 24 or 48 h. Crude glycerol from biodiesel production was used as external carbon source to improve denitrification. Leachate mixture of 15 % v/v in municipal wastewater was found to be the optimum concentration at which no adverse effects were observed. Experiments without the use of external carbon source resulted in a low denitrification potential and a strong NO3 −-N and NO2 −-N accumulation. By contrast, denitrification was effectively achieved by using crude glycerol at the beginning of the anoxic phase, where a sCOD/NOx-N ratio of 5 was created. Comparing the different operation strategies applied, 6 h aeration and 2 h anoxic phase at the 48 h-cycle period scheme resulted in the greatest TKN, NH4 +-N, NO3 −-N and NO2 −-N removal efficiencies, estimated as 75.9, 75.7, 99.9 and 99.9 %, respectively. For efficient phosphorus removal, sufficient time for the reduction of nitrate concentration (below 5 mg/L NO3 −-N) and the highest PO4 3−-P release at the non-aeration stage was needed in order to favor a poly-P enriched biomass. In conclusion, an intermittently aerated SBR working at various aerobic/anoxic duration phases was used to treat a mixture of wastewater and semi-mature landfill leachate. Glycerol added as external carbon source was necessary to complete denitrification. Enhanced phosphorus removal was achieved at sufficient anoxic phase duration (2–3 h).

Simultaneous removal of nitrogen, phosphorus and COD in an integrated OCO reactor

An integrated OCO reactor with two side-ditch separators based on the anaerobic/anoxic/oxic (A2/O) process was developed for municipal wastewater treatment in this study. The effects of dissolved oxygen (DO) concentration, hydraulic retention time (HRT) and the ratio of chemical oxygen demand (COD) to total nitrogen (C/N) in the influent were investigated for optimization, in order to achieve the removal of total nitrogen (TN), total phosphorus (TP) and COD in the reactor simultaneously. When the DO concentration of 2.0 mg/L in the aerobic zone, HRT of 12 h and C/N ratio of 8:1 were applied in the reactor, the superior removal efficiencies of COD, TN and TP reached 96%, 81% and 92%, respectively. The modification in integrated OCO system was characterized by the mixing of the liquid refluxed from anoxic and aerobic zones with the influent in the anaerobic zone. And the risk of activated sludge bulking was decreased successfully by enhancing phosphorus removal without any chemical auxiliary methods. Quite precise prediction results with the correlation coefficients (R) of 0.9584–0.9948 were forecasted by the back-propagation neural network model. All the results indicated that the integrated OCO process is able to remove TN, TP and COD in a reactor simultaneously.

Simplified phosphorus kinetic modeling: predicting changes in predialysis serum phosphorus concentration after altering the hemodialysis prescription

The KDIGO work group recommends increasing dialytic phosphorus removal in Stage 5D chronic kidney disease patients with persistent hyperphosphatemia; however, optimal prescriptions to enhance phosphorus removal by hemodialysis (HD) therapies have not yet been established. This study evaluated whether phosphorus kinetic modeling based on a pseudo one-compartment model could provide practical clinical guidance for predicting changes in predialysis serum phosphorus concentration after altering the HD prescription. Patient-specific phosphorus kinetic parameters determined from thrice weekly HD treatments on 774 patients in the HEMO Study were used to predict changes in predialysis serum phosphorus concentration after altering the HD prescription from thrice weekly to short daily and long nocturnal HD therapies. The effect of changes in the oral phosphorus binder prescription on predicted changes in the predialysis serum phosphorus concentration was also illustrated using the concept of equivalent phosphorus binder dose. Decreases in predialysis serum phosphorus concentration from thrice weekly HD to short daily and long nocturnal HD prescriptions demonstrated strong associations with the predialysis serum phosphorus concentration during thrice weekly HD that were relatively independent of patient-specific phosphorus kinetic parameters. Thus, the percent decrease in predialysis serum phosphorus concentration was approximately the same among patients for a given alteration in the HD prescription. Both increased weekly treatment time and frequency resulted in a reduction in the predialysis serum phosphorus concentration; however, the effect of treatment time was more influential. Simultaneous reduction in the effective phosphorus binder dose blunted the decrease in the predialysis serum phosphorus concentration. This study demonstrated that a simplified form of phosphorus kinetic modeling based on a pseudo one-compartment model can provide practical clinical guidance for predicting changes in predialysis serum phosphorus concentration after altering the HD prescription. Prospective validation of this approach in future studies is warranted.

Enhanced phosphorus removal from sewage in mesocosm-scale constructed wetland using zeolite as medium and artificial aeration

Phosphorus (P) contained in sewage maybe removed by mesocosm-scale constructed wetlands (MCW), although removal efficiency is only between 20% and 60%. P removal can be enhanced by increasing wetland adsorption capacity using special media, like natural zeolite, operating under aerobic conditions (oxidation-reduction potential (ORP) above+300 mV). The objective of this study was to evaluate P removal in sewage treated by MCW with artificial aeration and natural zeolite as support medium for the plants. The study compared two parallel lines of MCW: gravel and zeolite. Each line consisted in two MCW in series, where the first MCW of each line has artificial aeration. Additionally, four aeration strategies were evaluated. During the operation, the following parameters were measured in each MCW: pH, temperature, dissolved oxygen and ORP. Phosphate () and chemical oxygen demand (COD), five-day biological oxygen demand (BOD5), total suspended solids (TSS) and ammonium. (NH 4+−N ) were evaluated in influents and effluents. Plant growth (biomass) and proximate analysis for P content into Schoenoplectus californicus were also performed. The results showed that removal efficiency was 70% in the zeolite medium, presenting significant differences (p<.05) with the results obtained by the gravel medium. Additionally, aeration was found to have a significant effect (p<.05) only in the gravel medium with an increase in up to 30% for removal. Thus, S. californicus contributed to 10–20% of P removal efficiency.

Phosphorus Speciation and Treatment Using Enhanced Phosphorus Removal Bioretention

This field research investigated the water quality performance of a traditional bioretention cell retrofitted with 5% (by mass) water treatment residual (WTR) for enhanced phosphorus removal. Results indicate that WTR incorporation into the bioretention media does not negatively influence the infiltration mechanism of the bioretention system. Total suspended solids (TSS), total phosphorus (TP), and particulate phosphorus (PP) concentrations in runoff inflow were significantly reduced compared to outflow due to filtration of particulate matter. TP concentrations were significantly reduced by the bioretention cell; before WTR retrofit TP export occurred. Although net removal of soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) from incoming runoff was not found, leaching of dissolved phosphorus (DP) was prevented not only from incoming runoff, but also from the media and captured PP. Near constant outflow SRP and DOP concentrations suggest an equilibrium adsorption treatment mechanism. Both event mean concentrations and mass loads were reduced for TSS and all P species. Pollutant mass removals were higher than the event mean concentration removals due to the attenuation of volume by the bioretention media.

Contaminant removal performances on domestic sewage using modified anoxic/anaerobic/oxic process and micro-electrolysis

The objective of this study was to enhance removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) from domestic sewage in a sequencing batch reactor with added new materials. A modified anoxic/anaerobic/oxic (MAAO) process, integrating a micro-electrolysis (ME) bed in an anoxic tank, and complex biological media (CBM) in anoxic, anaerobic and oxic tanks to treat domestic sewage, and their performances were investigated. The MAAO system was operated at controlled hydraulic reTENTion time (HRT) of 8 h and mixed liquor recirculation (MLR) at 75%. The results showed that the MAAO system could effectively remove COD, TN and TP with average rates of 93%, 80% and 94%, respectively, in March, and 94%, 76% and 91%, respectively, in August. In this system, TP was primarily removed from the anoxic tank regardless of the operational conditions; removal contribution ratios to TP of the anoxic tank reached 56% both in March and August, indicating that the ME bed can effectively enhance phosphorus removal. TN was primarily removed from the anoxic and anaerobic tanks; removal contribution ratios to TN of anoxic and anaerobic tanks reached 36–38% and 37–38%, respectively. The oxic tank had the highest share of COD removal (56% both in March and August) in the removal of phosphorus. The outflow concentrations of COD, TN and TP were 3–46, 7–14 and 0.3–0.5 mg/L, respectively, in March, and 26–49, 9–15 and 0.04–0.1 mg/L, respectively, in August. COD and TN removal performances indicated that the innovative materials of the ME bed and CBM can effectively enhance COD and TN removal.

Study on Potassium Ferrate and Ferric Sulfate Combined with Enhanced Phosphorus Removal

Through the experiment about the potassium ferrate joint polymeric ferric sulfate removing phosphorus , add a small amount of potassium ferrate can significantly improve the phosphorus removal rate, study the optimum process conditions of the experiment about removing phosphorus, in order to make phosphorus contented in water treated reach A standard of the national urban sewage discharge standards.

Active slag filters: rapid assessment of phosphorus removal efficiency from effluent as a function of retention time

There is increasing pressure to upgrade effluent ponds for phosphorus removal. Active slag filters offer a solution, but design information is limited. Hydraulic retention time (HRT) is a key factor in filter design because it controls filter treatment efficiency as well the filter substrate lifespan. This paper reports on a rapid method of continual looping of effluent through a filter column to obtain a relationship between HRT and phosphorus removal efficiency. Phosphorus removal declined logarithmically with respect to retention time. While the mechanisms that yield this relationship involve complex mass transfer and adsorption of phosphorus to Fe oxyhydroxide sites, in general terms, the adsorption rate is proportional to the adsorbate effluent concentration. Waste stabilization pond effluent treated by the slag achieved phosphorus removal efficiencies over 90% at extended HRTs greater than 70 hours, while 80% removal was obtainable in 30 hours. Higher phosphorus removal was achieved for slag treating real effluent compared with synthetic phosphate solution. This can be explained by: (1) different starting phosphorus concentrations in the synthetic phosphate solution and real effluent; and (2) the presence of constituents in real effluent that can enhance phosphorus removal, such as oxidized iron compounds, cations, algae and humic complexes. This new technique, which proved capable of replicating treatment efficiencies obtained from long-term column studies, offers rapid assessment of phosphorus removal efficiency as a function of retention time and thus will enable design engineers to size active filters on the basis of achieving the required phosphorus removal standards.

Impact of Iron Salt Dosage to Sewers on Downstream Anaerobic Sludge Digesters: Sulfide Control and Methane Production

The addition of iron salts to sewers for sulfide control has a significant impact on downstream wastewater-treatment performance, in which iron ions can be resolubilized from iron sulfide precipitates in aeration tanks to precipitate phosphate, thus enhancing phosphorus removal from the wastewater. In this study, the impact of iron salt dosage to sewers on the performance of anaerobic sludge digesters was investigated at bench scale. Anaerobic digesters were fed with mixed primary sludge, activated sludge, and sludge that contained ferric phosphate precipitates, formed by aerating iron sulfide- and phosphate-containing wastewater with activated sludge. In anaerobic conditions, ferric ions were released from ferric phosphate precipitates and utilized for a third time to precipitate sulfide that formed during sludge digestion, which ultimately resulted in complete control of H2S emissions from digesters. The results indicate that iron salt addition to sewers at typical dosing rates (e.g., 5-20 mgFeL −1 ) would provide an excessive quantity of iron salts for sulfide control in sludge digesters. Methane production and other digestion processes were not negatively impacted by iron addition to the wastewater. DOI: 10.1061/(ASCE) EE.1943-7870.0000650. © 2013 American Society of Civil Engineers. CE Database subject headings: Hydrogen sulfides; Anaerobic treatment; Sewers; Iron compounds; Methane; Sludge. Author keywords: Hydrogen sulfide; Anaerobic sludge digestion; Sewers; Iron addition; Methane production.

Impacts of alum addition on the treatment efficiency of cloth-media MBR

Effects of alum addition on the treatment performance of cloth-media membrane bioreactor were investigated. At Mixed Liquor Suspended Solids (MLSS) of 3.5g/L and permeate flux of 16.3Ll/m2.h, the addition of alum at 7.5mg Al2(SO4)3/L (R2) and 15mg Al2(SO4)3/L (R3) enhanced phosphorus removal from 45% in control with zero alum (R1) to 58 and 69% in R2 and R3, respectively. Alum did not affect the removal efficiency of other treatment parameters which record an average of 99% for turbidity, TSS and ammonia, an average of 96% for COD and an average of more than 97% for TKN. Alum addition also significantly reduced sludge volume index (SVI) and particle size distribution (PSD) range and inhibited growth of filamentous bacteria. The results show that the best range for the particle size which reflects good settling properties is between 35–55 and 240–290μm. In the batch experiments, alum doses above 60mg/L have toxic effect on the autotrophic bacteria with significant reduction in ammonia oxidation and TKN removal. Under the operating condition of vigorous aeration of sludge biomass the addition of alum did not affect the flocculation process in the aeration tanks.

백운석 첨가가 응집에 의한 하수 처리수의 인 제거에 미치는 영향

Wastewater treatment plants need to reduce phosphorus in order to meet increasingly stringent regulations on phosphorus. This study evaluated the feasibility of dolomite as a coagulation aid to enhance phosphorus removal from secondary treated wastewater by chemical coagulation. Standard jar tests were conducted to evaluate the effect of dolomite addition on a coagulation process for phosphorus removal and to determine the optimum doses of coagulants and dolomite. Coagulants used with dolomite yielded a significant improvement in phosphorus removal and reduced total phosphorus concentrations below 0.02 mg/L in wastewater effluent. Dolomite has played an important role in enhancing phosphate adsorption and increasing pH, as a coagulation aid. The maximum removal efficiency of phosphorus in this study was yielded at 25 mg/l of dolomite and 20 mg Al/L of PAC dose. However, considering economic aspects, the optimum doses of dolomite and PAC were 10 mg/L and 15mg Al/L, respectively. Consequently, dolomite, a coagulation aid, can be used in coagulation processes to enhance the removal of phosphorus.

Characterizing membrane foulants in MBR with addition of polyferric chloride to enhance phosphorus removal

The effect of polymeric ferric chloride (PFC) addition on phosphorus removal and membrane fouling were investigated in an anoxic/oxic submerged membrane bioreactor. The total phosphorus concentration in effluent averaged at 0.26mg/L with PFC addition of 10–15mg/L, while the rate of membrane fouling increased 1.6 times over the control MBR (without PFC addition). Three-dimensional excitation–emission matrix fluorescence spectroscopy and Gel Filtration Chromatography analysis indicated that soluble microbial byproduct-like materials and large molecules (MW>100kDa) were one of the main contributors of biofouling. Fourier transform infrared spectrum confirmed that the major components of the cake layer were proteins and polysaccharides materials. Scanning electron microscopy demonstrated that membrane surfaces were covered with compact gel layer formed by organic substances and Energy Dispersive X-ray analysis indicated that ferric metals were the most important inorganic pollutants. Consequently, soluble organic substances and dose of PFC should be controlled to minimize membrane fouling.

Phosphorus Removal in Biological Aerated Filters by Chemically Enhanced

Phosphorus removal by biological aerated filter(BAF) is ineffective, its effluent TP is much more than 0.5mg/L, so chemically enhanced phosphorus removal is neccessary. To solve this problem, domestic wastewater through BAF by adding metal salts in the aerobic tank was studied. The ferric chloride and aluminum chloride were chosen as the metal salts. The results showed that: the removal rate of TP rose with the Me/P (Me=Fe, Al)mass ratio increased, the influence on other performance of BAF by chemically enhanced synchronously was not severe, with TP in the effluent below the standard of 0.5mg/L; to ensure the concentration of effluent TP was less than 0.5mg/L, the optimum mass ratios of dosing were Fe/P=3, Al/P=2.5; proper aeration intensity could maintain the proper micro-flocculation state in BAF, which was helpful to TP removal.

Enhanced phosphorus removal by a humus soil cooperated sequencing batch reactor using acetate as carbon source

The biological phosphorus removal by humus soil sequencing batch reactor process (HS-SBR) and a conventional sequencing batch reactor (cSBR) were compared using acetate as a sole carbon source. The HS-SBR was composed of a humus soil reactor (HSR) and a conventional SBR (designated as hsSBR). The HS-SBR showed a more stable and effective phosphorus removal with the efficiency of 97.3%, while as to the cSBR, it was 80%. However, in the HS-SBR for the removal of COD and nitrogen it was not improved. Moreover, in the anaerobic phase, the hsSBR had greater soluble orthophosphate (SOP) release and poly-β-hydroxybutyrate (PHB) synthesis capacity, but lower poly-β-hydroxyvalerate (PHV) synthesis and glycogen (Gly) degradation capacity than those in the cSBR. In addition, acetate (HAc) uptake rate and SOP release rate in the hsSBR were greater than those in the cSBR. In the aerobic phase, the PHA utilization efficiency for SOP uptake in the hsSBR was higher than the cSBR. All these observations suggested that adding the HSR improved the relative dominance of the phosphate accumulating organisms (PAOs) in the hsSBR.

Evaluation of a novel oxidation ditch system for biological nitrogen and phosphorus removal from domestic sewage

A novel oxidation ditch system using anaerobic tanks and innovative dual dissolved oxygen (DO) control technology is proposed for biological nitrogen and phosphorus removal from domestic sewage. A continuous bench-scale experiment running for more than 300 days was performed to evaluate the system. Monitoring and controlling the airflow and recirculation flow rate independently using DO values at two points along the ditch permitted maintenance of aerobic and anoxic zone ratios of around 0.30 and 0.50, respectively. The ability to optimize aerobic and anoxic zone ratios using the dual DO control technology meant that a total nitrogen removal efficiency of 83.2-92.9% could be maintained. This remarkable nitrogen removal performance minimized the nitrate recycle to anaerobic tanks inhibiting the phosphorus release. Hence, the total phosphorus removal efficiency was also improved and ranged within 72.6-88.0%. These results demonstrated that stabilization of the aerobic and anoxic zone ratio by dual DO control technology not only resulted in a marked improvement of nitrogen removal, but it also enhanced phosphorus removal.