Effluent Phosphorus Concentration Research Articles

Ithaca Area Wastewater Treatment Facility (IAWWTF) Tertiary Treatment Upgrades Before/After Impact Study: Effluent and Lake Phosphorus Results

Ithaca Area Wastewater Treatment Facility (IAWWTF) Tertiary Treatment Upgrades Before/After Impact Study: Effluent and Lake Phosphorus ResultsThe results of the IAWWTF tertiary treatment upgrade were analyzed by geostatistical analysis and Before/After impact studies. In May 2006, a tertiary treatment process was added to the IAWWTF treatment process. This upgrade has had a significant and positive effect on both the performance of the plant and on the water quality of southern Cayuga Lake. The effluent total phosphorus concentration...Author(s)Jose LozanoLynn SmithSourceProceedings of the Water Environment FederationSubjectSession 43: Nutrients: A Numbers GameDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2011ISSN1938-6478SICI1938-6478(20110101)2011:14L.2626;1-DOI10.2175/193864711802721271Volume / Issue2011 / 14Content sourceWEFTECFirst / last page(s)2626 - 2649Copyright2011Word count171

Changes in Polyhydroxy-Alkanoates (PHAs) during Enhanced Biological Phosphorus Removal with Dairy Industrial Wastewater

Using the industrial wastewater from a dairy plant, the performance of enhanced biological phosphorus removal (EBPR) with complex organic substances was evaluated. A laboratory-scale sequencing batch reactor (SBR) was operated and the organic loading rate in total chemical oxygen demand (tCOD) increased gradually from 200– 600 g-tCOD m−3 cycle−1 in three steps. As the organic loading increased, the food to microorganism ratio ( F/M ) increased from 0.16–0.27 (g-tCOD/g-MLVSS d). When it increased over 600 g-tCOD m−3 cycle−1 , the effluent phosphorus concentration fluctuated, showing an unstable EBPR activity. During the anaerobic condition, higher fraction of poly-3-hydroxyvalerate (PHV) was observed and the ratio of PHV to poly-3-hydroxybuyrate (PHB) production ( ΔPHV/ΔPHB ) ranged 1.2∼3.4 mM-C/mM-C . PHV was produced faster and used later than PHB. By applying fluorescent in situ hybridization (FISH) technique, the percentage of Rhodocyclus-related bacteria to the total cell counts was monitored as...

Steady-state model-based evaluation of sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process

Recently we developed a process for wastewater treatment in places where part of the fresh water usage is replaced by seawater usage. The treatment of this saline sewage consists of sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process. The process consists of an up-flow anaerobic sludge bed (UASB) for sulfate reduction, an anoxic filter for autotrophic denitrification using dissolved sulfide produced in the UASB and an aerobic filter for nitrification. The system was operated for 500 days with 97% COD removal and 74% total nitrogen removal without withdrawal of sludge. To verify these results and to understand this novel process, a steady-state model was developed from the COD, nitrogen and sulfur mass and charge balances based on the stoichiometries of the sulfate reduction, the autotrophic denitrification and the autotrophic nitrification. The model predictions agreed well with measured data on COD, nitrate and sulfate removal, sulfide production, effluent TSS, and mass balances of COD, sulfur and nitrogen in the three reactors. The model explains why withdrawal of sludge from the SANI system is not needed through comparisons of the predictions and measurements of effluent TSS and phosphorus concentrations.

Innovative phosphorus distribution method to achieve advanced chemical phosphorus removal

Since November 2006 a large-scale research project has been carried out at Wastewater Treatment Plant (WWTP) Leiden Zuidwest (within the Rijnland District Water Control Board). This research focuses on advanced removal of nutrients (phosphorus and nitrogen), heavy metals and priority hazardous substances from WWTP-effluent with different treatment techniques to reach an effluent quality, which could be required in the future by the Water Framework Directive (WFD) 2000/60/EC. Within the WFD-approach to guarantee an ecological and a chemical "good status" of the receiving water bodies, the focus is more and more on ultra low phosphorus concentrations in effluent. To be able to reach these stringent goals more insight into phosphorus components in effluent is required. A new method of distribution of phosphorus is used to determine orthophosphate, metal bound phosphorus, dissolved "organic" phosphorus and particulate "organic" phosphorus. This knowledge about the distribution of phosphorus makes it possible to compare different filter concepts and different process parameters, for example flocculation time, initial mixing energy and filtration rates. When comparing (filter concept 1) continuous sand filtration with (filter concept 2) dual media filtration for phosphorus removal, it appears that, a higher percentage of the formed metal bound phosphorus will pass the continuous sand filter. The ortho-phosphorus which is not bound to trivalent metal after coagulation will remain dissolved ortho-phosphorus and will pass the filter bed. This is shown in both filter concepts. The dissolved 'organic' phosphorus decreases after flocculation and the particulate 'organic' phosphorus increases which suggests that it may be colloidal or associated with colloidal material. With continuous sand filtration 50% of the particulate phosphorus is removed. In the dual media filter even 86% of the particulate phosphorus is removed.

Functionally Relevant Microorganisms to Enhanced Biological Phosphorus Removal Performance at Full‐Scale Wastewater Treatment Plants in the United States

The abundance and relevance ofAccumulibacter phosphatis (presumed to be polyphosphate-accumulating organisms [PAOs]), Competibacter phosphatis (presumed to be glycogen-accumulating organisms [GAOs]), and tetrad-forming organisms (TFOs) to phosphorus removal performance at six full-scale enhanced biological phosphorus removal (EBPR) wastewater treatment plants were investigated. Coexistence of various levels of candidate PAOs and GAOs were found at these facilities. Accumulibacter were found to be 5 to 20% of the total bacterial population, and Competibacter were 0 to 20% of the total bacteria population. The TFO abundance varied from nondetectable to dominant. Anaerobic phosphorus (P) release to acetate uptake ratios (P(rel)/HAc(up)) obtained from bench tests were correlated positively with the abundance ratio of Accumulibacter/(Competibacter +TFOs) and negatively with the abundance of (Competibacter +TFOs) for all plants except one, suggesting the relevance of these candidate organisms to EBPR processes. However, effluent phosphorus concentration, amount of phosphorus removed, and process stability in an EBPR system were not directly related to high PAO abundance or mutually exclusive with a high GAO fraction. The plant that had the lowest average effluent phosphorus and highest stability rating had the lowest P(rel)/HAc(up) and the most TFOs. Evaluation of full-scale EBPR performance data indicated that low effluent phosphorus concentration and high process stability are positively correlated with the influent readily biodegradable chemical oxygen demand-to-phosphorus ratio. A system-level carbon-distribution-based conceptual model is proposed for capturing the dynamic competition between PAOs and GAOs and their effect on an EBPR process, and the results from this study seem to support the model hypothesis.

Improved Computational Model (AQUIFAS) for Activated Sludge, Integrated Fixed‐Film Activated Sludge, and Moving‐Bed Biofilm Reactor Systems, Part III: Analysis and Verification

Research was undertaken to analyze and verify a model that can be applied to activated sludge, integrated fixed-film activated sludge (IFAS), and moving-bed biofilm reactor (MBBR) systems. The model embeds a biofilm model into a multicell activated sludge model. The advantage of such a model is that it eliminates the need to run separate computations for a plant being retrofitted from activated sludge to IFAS or MBBR. The biofilm flux rates for organics, nutrients, and biomass can be computed by two methods-a semi-empirical model of the biofilm that is relatively simpler, or a diffusional model of the biofilm that is computationally intensive. Biofilm support media can be incorporated to the anoxic and aerobic cells, but not the anaerobic cells. The model can be run for steady-state and dynamic simulations. The model was able to predict the changes in nitrification and denitrification at both pilot- and full-scale facilities. The semi-empirical and diffusional models of the biofilm were both used to evaluate the biofilm flux rates for media at different locations. The biofilm diffusional model was used to compute the biofilm thickness and growth, substrate concentrations, volatile suspended solids (VSS) concentration, and fraction of nitrifiers in each layer inside the biofilm. Following calibration, both models provided similar effluent results for reactor mixed liquor VSS and mixed liquor suspended solids and for the effluent organics, nitrogen forms, and phosphorus concentrations. While the semi-empirical model was quicker to run, the diffusional model provided additional information on biofilm thickness, quantity of growth in the biofilm, and substrate profiles inside the biofilm.

Recovery oriented phosphorus adsorption process in decentralized advanced Johkasou

Decentralized advanced wastewater treatment using adsorption and desorption process for recovery and recycling oriented phosphorus removal was developed. Adsorbent particles made of zirconium were set in a column, and it was installed as subsequent stage of BOD and nitrogen removal type Johkasou, a household domestic wastewater treatment facility. The water quality of the effluent of adsorption column in a number of experimental sites was monitored. The effluent phosphorus concentration was kept below 1 mg l(-1) during 90 days at all the sites. Furthermore, over 80% of the sites achieved 1 mg l(-1) of T-P during 200 days. This adsorbent was durable, and deterioration of the particles was not observed over a long duration. The adsorbent collected from each site was immersed in alkali solution to desorb phosphorus. Then the adsorbent was reactivated by soaking in acid solution. The reactivated adsorbent was reused and showed almost the same phosphorus adsorption capacity as a new one. Meanwhile, the desorbed phosphorus was recovered with high purity as trisodium phosphate by crystallization. It is proposed as a new decentralized system for recycling phosphorus that paves the way to high-purity recovery of finite phosphorus.

Modification of a Full‐Scale Sequencing Batch Reactor Operational Mode for Biological Nutrient Removal

Two biological nutrient removal modes, consisting of anaerobic, anoxic, and oxic sequences, were tested in a full-scale sequencing batch reactor. The modes, identified as BNR-S1 and BNR-S2, had average total nitrogen removals of 84 and 89%, respectively, for the months of August to October. Over the same period, total phosphorus removals for BNR-S1 and BNR-S2 were 88 and 87%, respectively. In contrast, total nitrogen and total phosphorus removals for the regular aerobic mode were 54.7 and 44.7%, respectively. When the wastewater temperature changed from approximately 20 to 15 degrees C in the winter months, total nitrogen and total phosphorus removals for BNR-S2 were reduced to 81 and 70%, respectively. Total nitrogen effluent concentrations were between 2.5 and 4 mg-N/L (at approximately 20 degrees C), while the effluent total phosphorus concentrations were between 1 and 2 mg/L. The BNR-S2 mode was found to require less energy per kilogram of soluble chemical oxygen demand removed than the regular and BNR-S1 modes.

Enhanced Biological Phosphorus Removal Performance and Microbial Population Changes at High Organic Loading Rates

A laboratory-scale sequencing batch reactor was operated and the dynamics of Rhodocyclus-related phosphorus-accumulating organisms (PAOs) population was monitored. After the system reached a steady state and showed a stable enhanced biological phosphorus removal status, the organic loading rate was increased from 160 to 1,020 g COD m−3 cycle−1 in five steps. When the P storage capacity reached maximum at 330 g COD m−3 cycle−1 , the system lost the stability and the effluent phosphorus concentration fluctuated. As the organic loading rate increased from 160 to 1,020 g COD m−3 cycle−1 , the PAO population decreased from 83.8±4.9 to 32.2±16.2 % and internal polyphosphate content decreased from 0.20 to 0.03 mg P mg VSS−1 . Phosphate-accumulating metabolism was weakened as the organic loading rate increased and PAO population decreased concomitantly, whereas glycogen-accumulating metabolism increased at high organic loading rates as supported by the increased intracellular glycogen content and production of a ...

Enhanced Biological Phosphorus Removal with P seudomonas putida GM6 from Activated Sludge

The enhanced biological phosphorus removal (EBPR) method is widely adopted for phosphorus removal from waste-water, yet little is known about its microbiological and molecular mechanisms. Therefore, it is difficult to predict and control the deterioration of the EBPR process in a large-scale municipal sewage treatment plant. This study used a novel strain isolated in the laboratory, Pseudomonas putida GM6, which had a high phosphate accumulating ability and could recover rapidly from the deteriorated system and enhance the capability of phosphorus removal in activated sludge. Strain GM6 marked with gfp gene, which was called GMTR, was delivered into a bench-scale sequencing batch reactor (SBR) of low efficiency, to investigate the colonization of GMTR and removal of phosphorus. After 21 days, the proportion of GMTR in the total bacteria of the sludge reached 9.2%, whereas the phosphorus removal rate was 96%, with an effluent concentration of about 0.2 mg L −1. In the reactor with the addition of GMTR, phosphorus was removed quickly, in 1 h under anaerobic conditions, and in 2 h under aerobic conditions. These evidences were characteristic of EBPR processes. Field testing was conducted at a hospital sewage treatment facility with low phosphorus removal capability. Twenty- one days after Pseudomonas putida GM6 was added, effluent phosphorus concentration remained around 0.3 mg L −1, corresponding to a removal rate of 96.8%. It was therefore demonstrated that Pseudomonas putida GM6couldbeused for a quick startup and enhancement of wastewater biological phosphorus removal, which provided a scientific basis for potential large-scale engineering application.

돼지 성장 및 육질 형질에 영향하는 종료웅돈의 효과

A submerged biofilm sequencing batch reactor (SBSBR) process, which liquor was internally circulated through sandfilter, was designed, and performances in swine wastewater treatment was evaluated under a condition of no external carbon source addition. Denitrification of NOx-N with loading rate in vertical and slope type of sandfilter was 19% and 3.8%, respectively, showing approximately 5 times difference, and so vertical type sandfilter was chosen for the combination with SBSBR. When the process was operated under 15 days HRT, 105L/hr.m3 of internal circulation rate and 54g/m3.d of NH4-N loading rate, treatment efficiencies of STOC, NH4-N and TN (as NH4-N plus NOx-N) was 75%, 97% and 85%, respectively. By conducting internal circulation through sandfilter, removal performances of TN were enhanced by 14%, and the elevation of nitrogen removal was mainly attributed to occurrence of denitrification in sandfilter. Also, approximately 57% of phosphorus was removed with the conduction of internal circulation through sandfilter, meanwhile phosphorus concentration in final effluent rather increased when the internal circulation was not performed. Therefore, It was quite sure that the continuous internal circulation of liquor through sandfilter could contribute to enhancement of biological nutrient removal. Under 60g/m3.d of NH4-N loading rate, the NH4-N level in final effluent was relatively low and constant(below 20mg/L) and over 80% of nitrogen removal was maintained in spite of loading rate increase up to 100g/m3.d. However, the treatment efficiency of nitrogen was deteriorated with further increase of loading rate. Based on this result, an optimum loading rate of nitrogen for the process would be 100g/m3.d.

연속순환 생물막 공정을 이용한 돈사 폐수 처리

반응물을 연속적으로 내부 순환시키는 생물막 연속회분식모래여과 공정을 고안하고 외부 탄소원이 전혀 사용되지 않는 조건하에서의 돈사폐수 처리특성을 평가하였다. 수직형과 경사형 모래여과조에서의 NOx-N 부하량에 따른 탈질율은 각각 19%와 3.8%로 수직형에서 5배 정도 높은 효율을 보임에 따라 수직형태의 모래여과조를 생물막 연속회분식 공정과 연계하여 운전하였다. 처리공정을 HRT 15일, 내부순환율 105L/hr.m3, 평균 암모니아성 질소 부하량 54g/m3.d 조건에서 운전하였을 때 STOC, NH4- N, TN의 처리효율은 각각 75%, 97%, 85%이었다. 생물막 연속회분식 반응조와 모래여과조간의 내부순환으로 TN의 제거효율이 약 14%증진되는 것으로 나타났으며 얻어진 질소제거효율 증진은 주로 모래여과조에서의 탈질에 의한 것으로 밝혀졌다. 또한 용해성 인의 경우 내부순환이 수행되지 않았을 시에는 유출수내 농도가 오히려 증가하였으나 내부순환시에는 약 57% 정도가 제거되는 것으로 나타남에 따라 반응물의 내부순환이 용해성 인의 제거효율 증진에도 기여함을 알 수 있었다. 시스템에서의 질소제거 양상을 분석해본 결과 최종 유출수내의 NH4-N은 부하량 60g/m3.d 수준에서 약 20mg/L 이하로 비교적 일정하였고 부하량이 100g/m3.d. 이상의 수준으로 상승함에도 80% 이상의 질소 제거효율을 보였다. 그러나 부하량 100g/m3.d 수준 이상에서부터 처리효율이 감소하는 것으로 나타나 외부탄소원이 전혀 사용되지 않는 운전조건에서의 질소의 적정 부하량은 약 100g/m3.d 정도인 것으로 판단되었다. A submerged biofilm sequencing batch reactor (SBSBR) process, which liquor was internally circulated through sandfilter, was designed, and performances in swine wastewater treatment was evaluated under a condition of no external carbon source addition. Denitrification of NOx-N with loading rate in vertical and slope type of sandfilter was 19% and 3.8%, respectively, showing approximately 5 times difference, and so vertical type sandfilter was chosen for the combination with SBSBR. When the process was operated under 15 days HRT, 105L/hr.m3 of internal circulation rate and 54g/m3.d of NH4-N loading rate, treatment efficiencies of STOC, NH4-N and TN (as NH4-N plus NOx-N) was 75%, 97% and 85%, respectively. By conducting internal circulation through sandfilter, removal performances of TN were enhanced by 14%, and the elevation of nitrogen removal was mainly attributed to occurrence of denitrification in sandfilter. Also, approximately 57% of phosphorus was removed with the conduction of internal circulation through sandfilter, meanwhile phosphorus concentration in final effluent rather increased when the internal circulation was not performed. Therefore, It was quite sure that the continuous internal circulation of liquor through sandfilter could contribute to enhancement of biological nutrient removal. Under 60g/m3.d of NH4-N loading rate, the NH4-N level in final effluent was relatively low and constant(below 20mg/L) and over 80% of nitrogen removal was maintained in spite of loading rate increase up to 100g/m3.d. However, the treatment efficiency of nitrogen was deteriorated with further increase of loading rate. Based on this result, an optimum loading rate of nitrogen for the process would be 100g/m3.d.

Phosphorus Removal Characteristics in Hydroxyapatite Crystallization Using Converter Slag

This study was performed to investigate the phosphorus removal characteristics in hydroxyapatite (HAP) crystallization using converter slag as a seed crystal and the usefulness of a slag column reactor system. The effects of alkalinity, and the isomorphic-substitutable presence of ionic magnesium, fluoride, and iron on HAP crystallization seeded with converter slag, were examined using a batch reactor system. The phosphorus removal efficiencies of the batch reactor system were found to increase with increases in the iron and fluoride ion concentrations, and to decrease with increases in the alkalinity and magnesium ion concentration. A column reactor system for HAP crystallization using converter slag was found to achieve high, stable levels of phosphorus elimination: the average PO4-P removal efficiency over 414 days of operation was 90.4%, in which the effluent phosphorus concentration was maintained at less than 0.5 mg/L under the appropriate phosphorus crystallization conditions. The X-ray diffraction (XRD) patterns and Fourier transform infrared (FTIR) spectra of the crystalline material deposited on the seed particles exhibited peaks consistent with HAP. Scanning electron micrograph (SEM) images showed that finely distributed crystalline material was formed on the surfaces of the seed particles. Energy dispersive X-ray spectroscopy (EDS) mapping analysis revealed that the molar Ca/P composition ratio of the crystalline material was 1.72.

NON-DIAGONAL MULTIVARIABLE ROBUST QFT CONTROL OF A WASTEWATER TREATMENT PLANT FOR SIMULTANEOUS NITROGEN AND PHOSPHORUS REMOVAL

This paper presents the application of a robust non-diagonal multivariable control design method, based on the Quantitative Feedback Theory (QFT), to the control of a complex wastewater treatment plant (WWTP) with biological removal of nitrogen and phosphorus. The control objective is to simultaneously regulate the concentration of ammonia, nitrates and phosphorus in the plant effluent. The manipulated variables are the dissolved oxygen (DO) level in the aerobic reactor, the sludge recycling flow from the settler and the amount of ferric hydroxide added to chemically precipitate the phosphorus. Thus, the system becomes a three-input-three-output control structure with model parameter uncertainty. A robust non-diagonal multivariable QFT method is used to design a fully populated matrix controller. This sequential method reduces the interactions between control loops, increases the robust stability and fulfils the robust performance specifications defined by the user. It also considers non-minimum phase aspects by avoiding the introduction of right-half plane transmission zeros due to the controller elements. Simulations carried out by using the IWA ASM2d model under WEST® software validate the proposed control methodology.

Experience from 10 years of full-scale operation with enhanced biological phosphorus removal at Öresundsverket

Ten years of full-scale experience with enhanced biological phosphorus removal (EBPR) has been evaluated. During the start-up period lack of carbon source was the main operational problem and a higher level of volatile fatty acids was secured by introducing a primary sludge hydrolysis. Acidic thermal sludge hydrolysis was used as the sludge treatment method at the plant during about three years. One effluent stream, rich in carbon and precipitant, was brought back to the process leading to an improvement of the phosphorus removal both by an improved biological process and chemical precipitation. A quite stable process of EBPR was developed with low levels of effluent phosphorus concentration. Stringent effluent discharge limits during short evaluation periods necessitated a continued work for improvement of the short-term stability. During periods with lack of carbon, such as industrial holiday or rainy periods, both simultaneous precipitation and reduced aeration have been successfully tested as strategies for securing low levels of effluent phosphorus.

Optimization of Enhanced Biological Phosphorus Removal after Periods of Low Loading

Enhanced biological phosphorus removal is a well-established technology for the treatment of municipal wastewater. However, increased effluent phosphorus concentrations have been reported after periods (days) of low organic loading. The purpose of this study was to evaluate different operating strategies to prevent discharge of effluent after such low-loading periods. Mechanisms leading to these operational problems have been related to the reduction of polyphosphate-accumulating organisms (PAOs) and their storage compounds (polyhydroxy alkanoates [PHA]). Increased effluent phosphorus concentrations can be the result of an imbalance between influent loading and PAOs in the system and an imbalance between phosphorus release and uptake rates. The following operating conditions were tested in their ability to prevent a reduction of PHA and of overall biomass during low organic loading conditions: (a) unchanged operation, (b) reduced aeration time, (c) reduced sludge wastage, and (d) combination of reduced aeration time and reduced sludge wastage. Experiments were performed in a laboratory-scale anaerobic-aerobic sequencing batch reactor, using acetate as the carbon source. Without operational adjustments, phosphorus-release rates decreased during low-loading periods but recovered rapidly. Phosphorus-uptake rates also decreased, and the recovery typically required several days to increase to normal levels. The combination of reduced aeration time and reduced sludge wastage allowed the maintenance of constant levels of both PHA and overall biomass. A mathematical model was used to explain the influence of the tested operating conditions on PAO and PHA concentrations. While experimental results were in general agreement with model predictions, the kinetic expression for phosphorus uptake deviated significantly for the first 24 hours after low-loading conditions. Mechanisms leading to these deviations need to be further investigated.

Application of small community sewer system for improving the quality of the water resource in Korea

An existing SBR plant in a rural area was retrofitted from a conventional fill-and-draw system to an intermittent-aeration system for additional nitrogen removal. This study indicated that organic and nitrogen removal efficiency was improved over that before the retrofitting. But effluent phosphorus concentration was increased gradually with the operating time. In the latter period of investigation, phosphorus concentration in effluent was higher than influent. It was regarded that an excessively accumulated phosphorus was released again under the anaerobic conditions of the sludge storage tank. The application of the electro-coagulation process was investigated as an alternative method in order to prevent phosphorus from re-releasing. A laboratory test for electro-coagulation indicated that T-P removal was more stable than the biological method only. In addition, it was confirmed that T-N and organic materials as well as T-P were removed simultaneously by the electrochemical reaction in the bioreactor combined with electrolysis by more than the bioreactor only.

Performance of a hybrid SBR with fixed bed and suspended growth

A hybrid SBR system combined with fixed bed (media) and suspended growth zones was developed to improve both nitrogen and phosphorus removal. About 27% of the tank volume was filled with clay media to make a fixed bed in this system, and additional air was applied under the bed to wash the microbes from the media during the oxic stage to prevent the bed from clogging. This hybrid SBR system could eliminate the backwashing requirement for SBBR (sequencing batch biofilm reactor). This system showed a stable nitrification even at low temperature and shock load conditions. The specific reaction rates indicated the fixed bed zone had higher microbial activities for nitrification and denitrification, while the suspended growth zone had higher microbial activities for phosphorus release and uptake. In addition, the use of external sludge storage also increased both phosphorus and nitrogen removal. The effluent COD, nitrogen and phosphorus concentrations were respectively less than 15, 10.5 and 0.6 mg/L with weak sewage of 230 mg/L COD, 35 mg/L TKN and 5.3 mg/L TP.

Reduction of coagulant amount added to activated sludge for phosphorus removal

Adding coagulant to the activated sludge process is effective in maintaining the stability of phosphorus removal. However, the precise mechanisms of the reaction and behavior of coagulants and phosphorus are not well known. By introducing a new phosphorus removal model (PRM), the behavior of coagulant and phosphorus in the process could be described. The experimental data of the effluent phosphorus concentration and Fe content in the activated sludge agreed with the values calculated by PRM. The amount of coagulant addition to the activated sludge process for phosphorus removal is reduced with the enhanced biological phosphorus removal process. It is suggested that the amount of reduction is determined by using PRM.

Effect of sequentially combining methanol and acetic acid on the performance of biological nitrogen and phosphorus removal

A sequentially combined carbon (SCC) source using methanol and acetic acid was investigated for biological nitrogen and phosphorus removal in a wastewater treatment process consisting of an anoxic zone, an oxic zone and a final settling tank. The anoxic zone was divided into two separate anoxic zones to feed methanol in the first anoxic zone and acetic acid in the second anoxic zone. Methanol and acetic acid, each as the sole carbon source, were also tested for comparison. The use of SCC was superior in nitrogen removal with all combined COD ratios of methanol/acetic acid tested, yielding 95.8–97% efficiency (less than 1 mg N/l in the final effluent). The highest phosphorus removal of above 92% (final effluent concentration of 0.12 mg P/l) was achieved when only acetic acid was used at a quantity equivalent to 50 mg COD/l. However, when SCC was used, the acetic acid dosage of 50 mg COD/l could be reduced down to 20 mg COD/l when 30 mg COD/l was replaced by methanol; this resulted in a final effluent phosphorus concentration of 0.6 mg P/l. Additional benefits of SCC included the excellent sludge settling properties compared to the use of methanol or acetic acid alone.