Phosphorus Elimination Research Articles

CoAl-LDH on ZIF-67 template inserted into the conductive matrix as a high-efficiency composite anode for facilitating phosphorus elimination

Phosphorus pollution can induce water eutrophication and critically threaten the stability of the aquatic ecosystem. Capacitive deionization (CDI) is a potential candidate for controlling phosphorus levels due to its lack of chemical requirements, eco-friendliness, and low energy demand. Herein, a novel ZIF-67-derived CoAl-LDH embedded in conductive carbon skeletons (CoAl-LDH/C) was successfully constructed by a self-sacrificial template strategy. A conductive carbon matrix is incorporated into LDH, which can alleviate the insufficient conductivity and aggregation issues for LDH. The results revealed that CoAl-LDH/C possesses superior phosphorus elimination properties (qm=32.7 mg P/g) at 1.2 V, benefiting from its abundant active sites, large mesoporous diameter, specific surface area, total pore volume, outstanding specific capacitance, and ion diffusion. Meanwhile, the energy consumption of CoAl-LDH/C is merely 3.398 kWh/kg and 0.024 kWh/m3. CoAl-LDH/C also proved flexible for practical applications regarding complex water quality (wide pH range, coexisting substances, natural water) and cyclic utilization. Finally, the potential mechanism illuminated that the phosphorus elimination process in an electric field engages with ligand exchange, anion exchange, electrostatic attraction, and hydrogen bonds. This work paves a promising concept for designing innovative LDH-based electrodes with excellent ion diffusion and superior conductivity to eliminate phosphorus efficiently.

Novel three-sludge municipal wastewater treatment process coupling denitrifying phosphorus removal with anaerobic ammonium oxidation

The two-sludge anoxic dephosphation (DEPHANOX) process frequently encounters the challenge of elevated effluent ammonia levels in practical applications. In this study, the anaerobic ammonium oxidation (anammox) biofilm was introduced into the DEPHANOX system, transforming it into a three-sludge system, enabling synchronous nitrogen and phosphorus elimination, particularly targeting ammonia. Despite a chemical oxygen demand/total nitrogen ratio of 4.3 ± 0.8 in the actual municipal wastewater and 4.5 h of aeration, the effluent total nitrogen was 13.7 mg/L, lower than the parallel wastewater treatment plant. Additionally, the effluent ammonia reduced to 5.1 ± 2.5 mg/L. Notably, denitrifying phosphorus removal and anammox were coupled in the anoxic zone, yielding 74.5 % nitrogen and 87.8 % phosphorus removal. 16S rRNA gene sequencing identified denitrifying phosphorus-accumulating organisms primarily in floc sludge (Saprospiraceae 7.07 %, Anaerolineaceae 1.95 %, Tetrasphaera 1.57 %), while anammox bacteria inhabited the biofilm (Candidatus Brocadia 4.00 %). This study presents a novel process for efficiently treating municipal wastewater.

A Study on the Situation and Learnings of the Precipitant Shortage in the German Wastewater Sector

Wastewater treatment companies are particularly confronted by the energy and supply crisis resulting from the war in the Ukraine. More specifically, production and supply problems with precipitant production have shown that today’s wastewater treatment technology in Germany is not crisis-proofed and must become more resilient. The aim of this paper was to determine a required precipitant quantity for Germany with regard to chemical phosphorus elimination, as well as the expected shortfalls due to the shortage situation. Furthermore, possible solutions were identified for how the precipitant can be saved or substituted. Study surveys were conducted to gather data for a meaningful response regarding the operators (wastewater treatment plants, industry, and water suppliers), manufacturers, and the German federal states. A recommendation is given on what a path to more resilient wastewater management with a focus on phosphorus elimination could look like. Based on the data obtained, the report focused on wastewater engineering issues for wastewater treatment plants and industry. The results of the study are relevant for decision-makers, researchers, and operators in the wastewater sector in order to intervene in the market themselves if necessary, e.g., money for production or conversion to biological phosphorus elimination.

Efficient phosphorus recovery utilizing Magnesium-Modified Oil-Based drilling cutting Ash: Unraveling the role of ammonia nitrogen independent of struvite formation

A novel approach to phosphorus recovery is introduced in this study, employing alkali-melted and magnesium-modified oil-based drill cutting ash (AM-Mg-OBDCA) as highly efficient and cost-effective adsorbents. This innovation represents a notable stride in harnessing the resource potential of oil-based drill cutting ash (OBDCA). An investigation into the impact of ammonia nitrogen on phosphorus recovery was undertaken, revealing enhanced ammonia nitrogen removal in the presence of phosphorus. Simultaneously, the presence of ammonia nitrogen exhibited a favorable influence on phosphorus elimination across a broad pH range and in the co-presence of ions. Particularly under acidic conditions, AM-Mg-OBDCA demonstrated exceptional phosphorus adsorption efficiency. Conversely, co-existing carbonate ions were observed to significantly hinder phosphorus adsorption, while bicarbonate ions exerted only marginal inhibition on ammonia nitrogen adsorption. To discern the adsorption behavior, the pseudo-second-order and Langmuir models were applied, unveiling theoretical adsorption capacities of 161.8 mg/g and 98.81 mg/g for ammonia nitrogen and phosphorus onto AM-Mg-OBDCA, respectively. The forms of phosphorus in the spent AM-Mg-OBDCA were analyzed utilizing the Standard Measurement Test (SMT) phosphorus classification, shedding light on potential mechanisms governing phosphorus and ammonia nitrogen adsorption/co-adsorption. Investigation into the prospective reuse of AM-Mg-OBDCA as a fertilizer subsequent to phosphorus adsorption was conducted, bolstering its environmentally benign potential. In essence, this research introduces an inventive and efficacious strategy for repurposing OBDCA waste into functional materials with valuable applications. By tackling the challenges posed by phosphorus pollution and offering a pathway for resource utilization, this study makes a substantial contribution to the advancement of both environmental preservation and the development of sustainable materials.

Feasibility of natural wastewater treatment systems and life cycle assessment (LCA) for aquatic systems

Background: Natural wastewater treatment systems (NWTSs) in small villages are a major challenge for European water authorities. With growing social demands for environmental practices, evaluating the feasibility and environmental impact of low-cost treatment systems for small residential areas is essential. Methods: To address this challenge, this study was conducted to evaluate 10 NWTSs seasonally in rural areas of Bursa, Turkey. Authorities over the facilities permitted the examination of workable, low-cost effluent management options. Also, using Open-LCA software based on ReCiPe MidPoint (H) version 1.67, these plants’ effects on global warming, Phosphorus-depletion, human toxicity, marine eutrophication, and freshwater eutrophication were examined. Results: According to the LCA findings, Deydinler NWTS had a greater impact across all three effect areas (freshwater eutrophication, marine eutrophication, and human toxicity), ranging from 11 to 41%. Pinar and Yenice facilities, however, had 26% and 27% larger impacts in the same two impacts (marine eutrophication and human toxicity). These systems performed on average at 67%, 50%, and 58% chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) elimination, respectively. Conclusion: According to the findings, 10 NWTSs have a treatment efficiency of about 70%. NWTSs are possibilities for decentralized wastewater treatment in small residential areas that are both cost-effective and environmentally favorable. By treating organic pollution naturally, without chemicals, and with minimal energy use, they lessen their negative environmental effects. The main findings of this study will be useful for academics in determining future research areas and identifying whom they might consult to help design carbon footprint of NWTS and future carbon reduction objectives.

Controlled mechanism and removal performance of phosphorus in black and odorous water bodies by Fe-based layered double hydroxides

The effective approach for controlling internal phosphorus loading remains a longstanding challenge to the maintenance of remediated black and odorous water bodies. Here, three Fe-based LDHs materials were developed for alleviating the phosphorus pollution in black and odorous water through synergistic functions of phosphate adsorption, controlled release of phosphorus, and microbial metabolism. The mechanism of phosphate removal in overlying water is mainly specific electrostatic attraction and coordination. After the addition of Fe-based LDHs, the water quality indexes of black and odorous water bodies were significantly improved, including TP concentration (from 0.8 to 0.2 mg/L), the dissolved oxygen content (from 0.1 to 3.0 mg/L), COD, turbidity (from 34 to 18 FTU), and redox potential. Moreover, the morphology and physicochemical properties of sediments were regulated by Fe-based LDHs. Fluffier and smaller sediments particles due to the destruction of extracellular polymeric substances structure, which was beneficial to the release of endogenous phosphorus. Furthermore, the results of microbial community structure analysis illustrated that Proteobacteria and Dechloromonas played the most important role in phosphorus elimination in Fe-based LDHs system. That is, based on the biocompatibility of Fe-based LDHs, which act as a medium of the electron transfer in the microbial metabolism, combining with microorganisms for the synergistic remediation of black and odorous water bodies. Our study emphasizes the feasibility of Fe-based LDHs materials for the remediation of internal phosphorus loads in black and odorous water bodies, towards sustainable control.

Formation of vivianite in digested sludge and its controlling factors in municipal wastewater treatment

Engineering solutions to recover phosphorus from municipal wastewater are required to close the anthropogenic phosphorus cycle. After chemical phosphorus elimination by iron, the ferrous iron‑phosphorus mineral vivianite forms in digested sludge, and its separation is being researched at the pilot scale. In this study, sludge samples from 16 wastewater treatment plants (WWTPs) demonstrated that phosphorus bound to biomass and redox-sensitive iron in activated sludge was transformed into other phosphorus binding forms, including vivianite, during digestion. Vivianite quantity was approximated using X-ray diffraction and two sequential extractions. These three independent methods of approximating vivianite quantity were closely related confirming their relationship to the vivianite content in the samples. The digested sludge from three WWTPs exhibited comparatively high levels of vivianite-bound phosphorus approximated between 31 % and 51 % of total phosphorus. The controlling factors of vivianite formation were investigated in order to enhance its formation in digested sludge and increase the amount of phosphorus recoverable as vivianite. They were identified using single and multivariate correlation (MLR), considering the sludge properties, sludge composition, and process parameters within the operating range of the 16 WWTPs. Increasing iron content was verified as the primary predictor of significantly increased vivianite formation (MLR: p < 0.001). In addition, increasing sulphur content was found to be an additional significant factor that decreased vivianite formation (MLR: p < 0.05). Furthermore, a comparison of plants using sulphur-free (FeCl2 and FeCl3) and sulphur-containing (FeSO4 and FeClSO4) precipitants indicated that the latter could increase the sulphur content in digested sludge (one-tailed Welch two-sample t-test: t(14.6) = 2.3, p = 0.02). Thus, by increasing the sulphur content, the use of sulphur-comprising precipitants may counteract vivianite formation, whereas sulphur-free precipitants may facilitate it and, hence, promote vivianite recovery.

Variation of the element composition of municipal sewage sludges in the context of new regulations on phosphorus recovery in Germany

Phosphorus (P) recovery is obligatory for all sewage sludges with more than 20 g P/kg dry matter (DM) from 2029 in Germany. Nine wastewater treatment plants (WWTPs) were chosen to investigate variations of phosphorus contents and other parameters in sewage sludge over the year. Monthly sewage sludge samples from each WWTP were analyzed for phosphorus and other matrix elements (C, N, H, Ca, Fe, Al, etc.), for several trace elements (As, Cr, Mo, Ni, Pb, Sn) and loss of ignition. Among the nine WWTPs, there are four which have phosphorus contents both above and below the recovery limit of 20 g/kg DM along the year. Considering the average phosphorus content over the year, only one of them is below the limit. Compared to other matrix elements and parameters, phosphorus fluctuations are low with an average of 7% over all nine WWTPs. In total, only hydrogen and carbon are more constant in the sludge. In several WWTPs with chemical phosphorus elimination, phosphorus fluctuations showed similar courses like iron and/or aluminum. WWTPs with chamber filter presses rather showed dilution effects of calcium dosage. As result of this study, monthly phosphorus measurement is highly recommended to determine whether a WWTP is below the 20 g/kg DM limit.Graphical

Enhanced nutrient removal from mainstream sewage via denitrifying dephosphatation, endogenous denitrification and anammox in a novel continuous flow process

It is a challenging subject to realize nitrogen and phosphorus elimination synchronously from limited-carbon sewage through conventional biological processes. Herein, a novel continuous flow anaerobic/oxic/anoxic/oxic (AOA-O) process, which integrated denitrifying dephosphatation, endogenous denitrification and anammox in the anoxic zone, was developed to enhance nutrient elimination from low carbon/nitrogen sewage (3.4 in average). After the long-term operation (280 days), a satisfactory nutrient removal performance (effluent PO43--P: 0.2 mg P/L, total inorganic nitrogen (TIN):8.9 mg N/L) was obtained. Mass balance indicated that anammox contributed to 26.1% TIN removal and denitrifying dephosphatation contributed to 25.6% phosphorus removal, respectively. The cooperation of anammox bacteria retained in biofilms and endogenous denitrifying bacteria in flocculent sludge was responsible for the enhanced nutrient removal in the anoxic zone. Dechloromonas carried out phosphorus uptake both under oxic conditions and anoxic conditions. This study can broaden the application prospect of mainstream anammox.

Phosphorus recycling from activated sludge of full-scale wastewater treatment plants by fast inversion of the biological phosphorus elimination mechanism

Enhanced biological phosphorus removal (EBPR) is often applied by wastewater treatment plants (WWTPs) whereby phosphorus (P) is accumulated in the activated sludge (AS) biomass. The German Sewage Sludge Ordinance demands that large WWTPs recycle P from their process streams by 2029. This study aimed at evaluating the potential of an acetate-mediated P re-dissolution from non-acclimated AS of three full-scale WWTPs. All AS exhibited enhanced P re-dissolution during acetate uptake and followed kinetics typical of EBPR systems. Re-dissolution efficiency differed depending on the WWTP operation mode. The highest P re-dissolution yield (56% of total P) was obtained for pure EBPR sludge. Lower re-dissolution rates of 19–22% were observed in the AS from WWTPs that employed additional chemical P removal, probably due to shortage of intracellular polyphosphate. Pure EBPR systems may be suited for the implementation of a re-dissolution based strategy for P recycling from AS where P depleted AS could potentially be returned to the biological treatment stage.

Graphene-Based Composites for Phosphate Removal.

A variety of methods, including chemical precipitation, biological phosphorus elimination, and adsorption, have been described to effectively eliminate phosphorus (P) in the form of phosphate (PO43–) from wastewater sources. Adsorption is a simple and easy method. It shows excellent removal performance, cost effectiveness, and the substantial option of adsorbent materials. Therefore, it has been recognized as a practical, environmentally friendly, and reliable treatment method for eliminating P. Nanocomposites have been deployed to remove P from wastewater via adsorption. Nanocomposites offer low-temperature alteration, high specific surface area, adjustable surface chemistry, pore size, many adsorption sites, and rapid intraparticle diffusion distances. In this Mini-Review, we have aimed to summarize the last eight years of progress in P removal using graphene-based composites via adsorption. Ultimately, future perspectives have been presented to boost the progress of this encouraging field.

The Efficiency of Biological Total Phosphorus Removal Process

This article investigates the efficiency of phosphorus removal in the municipal wastewater treatment plants in five counties of Romania from 2013 to 2017. This study focused on evaluation of the performance of phosphorus elimination using biological methods in order to respect the admissible effluent discharge limits. The yearly average of inflow total phosphorus varies from 3.64 mg/L to 4.22 mg/L comparing with 1.02 mg/ L and 1.59 mg/L the average of outflow. Chemical and biological methods are utilized to remove phosphorus. The efficiency of the numerous process available for the phosphorus removal is quite inadequate by comparing the effluent degree of purification and the removal cost.

Upgrading Hydrothermal Carbonization (HTC) Hydrochar from Sewage Sludge

As a treatment method of sewage sludge, the hydrothermal carbonization (HTC) process was adopted in this work. HTC has a great advantage considering the economic efficiency of its process operation due to its reduced energy consumption and production of solid fuel upgraded through the increased fixed carbon and heating value. The ash of sewage sludge, however, contains up to 52.55% phosphate, which degrades the efficiency of the thermochemical conversion process such as pyrolysis, combustion, and gasification by causing slagging. In this study, three kinds of organic acids, i.e., oxalic, tartaric, and citric acid, were selected to eliminate phosphorus from hydrochars produced through the HTC of sewage sludge. The efficiency of the phosphorus removal and the properties of the corresponding HTC hydrochars were analyzed by adding 20 mmoles of organic acids per 1 g of phosphorus in the HTC sample. In addition, the phosphorus reduction effect and the applicability to an upgrading process were verified. Oxalic acid was selected as the most appropriate organic acid considering the economic efficiency of its process operation. Furthermore, the optimal conditions were selected by analyzing the efficiency of the phosphorus elimination and the characteristic property of the HTC hydrochars with the weight fraction of oxalic acid.

Phosphorus removal and recovery from water with macroporous bead adsorbent constituted of alginate-Zr4+ and PNIPAM-interpenetrated networks

Currently, there is a growing trend in employing natural biomaterials (e.g., alginate) to prepare a novel bead adsorbent for phosphorus (P) elimination. However, the utilization of alginate beads to remove and recover P from effluents possesses limitations associated with its physical characteristics such as a dense gel layer, poor mechanical strength and low stability. To overcome the limitations and improve the adsorption performances, we synthesized a novel alginate-derived bead constituted of PNIPAM network interpenetrated in alginate-Zr4+ network (PNIPAM/SA-Zr) decorated with polyethylene glycol as a pore-forming agent, and then investigated its ability to remove and recover P from effluents. The morphology, functional groups, surface area, and mechanical strength of the beads were evaluated by SEM, FTIR, BET, and swelling analysis. The adsorption of P was investigated by varying various factors. The adsorption kinetics, isotherms, and thermodynamics were studied. Particularly, the P-loaded beads exhibited a faster desorption rate under thermal stimulus, and remained good desorption efficiency and reusability within five consecutive cycles. Zeta-potential and XPS results revealed that the adsorption mechanisms were related to electrostatic interactions, ligand exchange, and the formation of inner-sphere complexes. The beads possessed favorable fixed-bed column operation performances for P removal and recovery from real wastewater.

Performance assessment of Etueffont (France) lagooning treatment system: Report from a 16-year survey

This study examined the lagooning treatment system of the Etueffont landfill (France) over a period of 16 years. Outflow concentrations in total suspended solids, biological oxygen demand (BOD5) and trace metal elements largely met outflow standards and were on average of 5, 8 and 6 times lower than those observed at inflow, respectively. In 2000, however, high levels of BOD5 were observed in both the influent and effluent, exceeding the authorized outflow limits. At that time the lagooning ponds were subjected temporarily to organic pollution, coinciding with the arrival of the first leachates from a new cell. Though the chemical oxygen demand (COD) and total organic carbon in the influent exceeded authorized limits, overall values conformed to official standards with outflow exhibiting mean concentrations four times lower than those observed at inflow. The first period took place just after the arrival from the new cell of young leachates containing a very high level of COD (>10,000 mg L−1), causing an organic overload that led to a temporary dysfunctioning of the treatment installation lasting approximately two years. Additionally, the COD in the leachates fell below the strictest limits (125 mg L−1) at the end of monitoring (2005–2009). The initial nitrogen load brought in by the influent decreased progressively over time, evidence of continuous degradation. At the end of monitoring, regardless of the arriving inflow load, the discharge presented stable concentrations of approximately 30 mg L−1, appearing to indicate that the limits for nitrogen elimination. Total phosphorus elimination was optimal as the concentrations at outflow were minimal throughout most of monitoring, even though the phosphorus load at inflow was from two to thirty-five times greater. Thus, the findings show that landfill leachates in the methanogenic phase can be treated efficiently by lagooning without risk to the surrounding environment.

Design and practical test of a compact phosphorus elimination module for freshwater RAS discharge water

Recirculating aquaculture systems (RAS) can emit total phosphorus (TP) concentrations in their discharge water, which exceed environmentally tolerated restrictions. A compact phosphorus (P) elimination module has been developed and its performance has been tested using the discharge water from a commercial scale freshwater RAS for pike perch (Sander lucioperca) production. To enable its widespread and easy use in practical conditions, the standard principle of chemical-physical phosphorus elimination was adapted to the conditions prevalent in RAS operations. The effect of different precipitants and flocculants in RAS discharge water was studied in laboratory trials. When it came to the TP-elimination performance and the environmental impact, the combination of iron(III) chloride and calcium hydroxide proved highly suitable as the precipitation and flocculation agents. Based on the results that were obtained, a commercial scale P-elimination module was designed. The module was equipped with a 500-L hopper-bottomed reaction tank, dosing units for the precipitation and flocculation agents and valves for the automatic discharge of sludge and cleared water. The TP-elimination potential in different operational modes and retention times was examined. The amounts of excess sludge and cleared water quality were evaluated. The designed 500 L P-elimination module works in automatic batch mode and enables operators to eliminate approx. 95% of the phosphorus emissions from the discharge water from a RAS for annual fish production of about 20 to 25 t. It was possible to achieve TP concentrations of below 1 mg L−1 in the module’s cleared water discharge.

Phosphorus Elimination at Sodium Silicate from Quartz Sand Roasted with Complexation using Chitosan-EDTA

A phosphorus elimination from sodium silicate solution has been studied. Phosphorus elimination was performed by adding chitosan-EDTA to remove cation phosphorus. Characterization of chitosan-EDTA material was performed using FT-IR, while the decreasing level of phosphorus content was analyzed by quantitative analysis using spectrophotometer UV-Vis refers to SNI 06-6989-2004. The results showed that the content of the sodium silicate can be reduced up to 67.1% through Chitosan-EDTA complexation with phosphorus.

Climate Change Demands Adaptive Management of Urban Lakes: Model-Based Assessment of Management Scenarios for Lake Tegel (Berlin, Germany)

Lakes are known to be strongly affected by climate change as a result of their sensitivity to atmospheric forcing. The combined response of urban lakes to climatic changes and to urbanization of the catchment may be further altered by water quality management measures. We studied Lake Tegel in Berlin, Germany as a representative urban lake profoundly influenced by intense water management measures and a resulting complex hydrodynamic situation: Lake Tegel is fed by nutrient-rich river discharges and effluents from a phosphorus elimination plant (PEP). We estimated changes in water temperatures, the Wedderburn number, and the buoyancy frequency, as well as concentrations of dissolved oxygen and phosphate under climate change using a one-dimensional vertical hydrodynamic model coupled to a water quality model. Further, we investigated how four management scenarios with varying discharges of the PEP could affect the lake system. In all simulations, water temperatures increased and summer stratification extended. The modeling results demonstrated that the water management system buffers the high nutrient supply from the river inflow and can effectively mitigate negative effects of climate change on Lake Tegel, thus highlighting its importance for the lake ecosystem.

Phosphorus Removal in Low-Flux Hemodialysis, High-Flux Hemodialysis, and Hemodiafiltration.

Phosphorus removal by hemoelimination procedure is a important mechanism to maintain phosphorus level in acceptable level in patients on dialysis. Phosphorus is removed by both diffusion and convection, but in clinical practice, it is not possible to differentiate the contribution of this two transport modalities. We used Gutzwiller formula to quantify the amount of removed phosphorus and compared it in low-flux hemodialysis (LFHD), high-flux hemodialysis (HFHD), and on-line hemodiafiltration (HDF). There were no significant differences in phosphorus predialysis concentration, duration of procedure, processed blood volume and ultrafiltration, e.g., factors, which could possibly influence phosphorus elimination. All three tested dialysis modes also did not differ in urea dialysis dose (Kt/V) as a parameter of small molecular weight removal (LFHD, 1.50 ± 0.04 vs HFHD, 1.5 ± 0.06 vs HDF, 1.5 ± 0.05). The amount of removed phosphorus in LFHD, HFHD, and HDF was 34.0 ± 1.2, 37.8 ± 1.6, and 38.3 ± 1.4 mmol, respectively. Statistically significant increase in phosphorus removal was seen only with use of high-flux membrane (HFHD and HDF) when compared with the low-flux one. No difference was, however, found between HFHD and HDF. It can thus be concluded that phosphorus removal in all three dialysis modes is a predominantly diffusive issue and contribution of convection to it is minor to negligible.

High Efficiency Phosphorus Flocculants Prepared with Red Mud for Treating Lake Water

In this study, different acid modification methods were used to prepare two types of inorganic flocculation compounds. First, under simulated wastewater conditions, the optimal input quantity for phosphorus elimination of flocculant #1 was 0.5 g/L, and the optimal agitation conditions were rapid agitation at 300 rpm for 60 s followed by slow agitation at 20 rpm for 15 min. The optimal input amount of flocculant #2 was 0.8 g/L, and the optimal agitation conditions were rapid agitation at 300 rpm for 30 s followed by slow agitation at 100 rpm for 10 min. Then they were used to treat water from the East Lake. The removal rates of TP, ammonia nitrogen, COD, and turbidity by flocculant #1 were 91.45%, 60.90%, 80.71%, and 93.05%, respectively; the corresponding removal rates by flocculant #2 were 92.74%, 58.49%, 76.92%, and 84.66%, respectively. The discharged water for both flocculants had TP and COD concentrations that met the type III standards in GB3838-2002.