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Red mud is a red-coloured, mud-like solid waste discharged from the industrial aluminium production process, which has a high output and is a pollutant. It exhibits a small particle size and a large specific surface area and contains active oxides. In this study, "red mud" and "phosphate" were used as keywords to retrieve research hotspots and progress for the red mud as a phosphate adsorbent in the past 10 y. CiteSpace and VOSviewer visual literature analysis software were used to cluster countries, institutions, authors, and keywords. Related patents showed that research on the phosphate adsorption performance of red mud has considerably increased since 2013 and that China has made a significant contribution. This paper summarises the main chemical composition and modification methods of red mud and collects from literature the relevant mechanism research and data on phosphate adsorption/desorption using red mud as an adsorbent. Summarising data on the microstructure of red mud adsorbent, it is found that there are few reports on red mud as adsorbent based on density functional theory. This study suggests that the problem of the steric hindrance of the red mud adsorbent in the phosphate adsorption process needs further research. [ABSTRACT FROM AUTHOR]

The wastewater discharges are increasing due to industrialization and rising in the standard of living of the population in the M'zab region. This study is interested in the treatment of urban wastewater with raw clay. Wastewater treatment requires a series of steps involving physical, physico-chemical and biological treatments. Among the largest wastes present in wastewater, the treatment must at least eliminate the major part of the carbon pollution. Clays are characterized by a high capacity for adsorption, ion exchange, and swelling as well as by a particular rheological property. According to the results obtained, the treatment of urban wastewater in the M'zab valley with clay is effective in the adsorption of mineral salts of calcium, sulfates, chlorides, etc... is due to the fixing of the particles on the clay. This treatment shows an efficiency of elimination of organic matter, obtained for BOD5 with a yield of 90% after 9 d of contact for iron reaches 100% and one notices a decrease in the COD as well 60% as of other parameters of pollution. Indeed, we notice that the kinetics of adsorption of the purified clay presents the best capacity than the raw clay arrives up to 82% for nitrates and 95% for orthophosphates. Wastewater treatment will not only reduce the cost of treatment but also contribute to the preservation of the environment. [ABSTRACT FROM AUTHOR]

Phosphorus is a commonly used compound in coatings; thus, wastewater from coating plants usually contains large amounts of phosphate. Given its unidirectionality in the ecological cycle, phosphorus must be removed from coating wastewater and recycled. Herein, phosphorus was removed and recovered from industrial coating wastewater through chemical precipitation. The effects and mechanisms of this removal and recovery using the iron salt, calcium salt, and iron-calcium salt methods were analyzed. When the proportion of iron in iron-calcium salt exceeded 0.51, the average phosphorus removal rate was more than 62.44% of the average removal rate when the iron salt or calcium salt was used alone. A synergistic phenomenon was demonstrated with the iron-calcium salt method; the phosphorus removal rate reached 96.13% when the molar ratio of iron-calcium salt to phosphorus was 1.50. The precipitation floccules produced using the iron-calcium salt integrated the advantages of the iron and calcium salt methods; they had a large particle size and were easily crystallized. This study demonstrates a valuable method for the removal and recovery of phosphorus from industrial coating wastewater. [ABSTRACT FROM AUTHOR]

Large amounts of nitrogen and phosphorus elements were discharged into the environment. They would lead to severe eutrophication of water bodies. The development of economically efficient, green and ecological adsorbents is the current focus for adsorption technology. In this research, the cost-effective biochar modified by Mg/Ca bimetallic oxide composites (Mg/Ca@PS) for adsorption of NO3- and PO43- ions in aqueous solution was investigated. Additionally, Mg/Ca@PS also was characterized by scanning electron microscopy, transmission electron microscopy, energydispersive X-ray analysis, X-ray diffraction, and Fourier-transform infrared spectroscopy, respectively. The experimental results showed that the adsorption process of NO3- ions in aqueous solution by Mg/Ca@PS could be described by pseudo-second-order kinetic model and Langmuir isotherm model, respectively. However, the adsorption process of PO43- ions in solution by Mg/Ca@PS could be described by pseudo-second-order kinetic model and Freundlich isotherm model, respectively. Additionally, the adsorption capacity of NO3- and PO43- ions in aqueous solution by Mg/Ca@PS were 18.52 and 47.85 mg/g, respectively. The adsorption mechanisms of NO3- ionsand PO43- ions in solution by Mg/Ca@PS mainly contain surface adsorption, intraparticle diffusion, electrostatic attraction, and ion exchange. Moreover, the adsorption mechanism of PO43- ions in solution by Mg/Ca@PS also includes chemical precipitation. In the five recycle times, the removal rate of NO3- and PO43- ions still reached 55.31% and 48.12%, respectively. It indicated that the chemical stability of Mg/Ca@PS was very well, and it was a good environmental friendly material. [ABSTRACT FROM AUTHOR]

In this study freely suspended, Ca-alginate immobilized Chlorella vulgaris cells and blank alginate beads were used for removal of Pb(II) from municipal wastewater. Experimental data showed that biosorption capacity of algal cells dependent on the operational condition such as pH, dosages, contact time and temperature. The maximum biosorption of Pb(II) was achieved with Ca-alginate immobilized algal cells at an optimum pH of 5, algal dosage of 3 g/L and contact time of 30 min at room temperature. Results revealed that biosorption rate initially increased rapidly, the optimal removal efficiency was reached within about 30 min. Increasing initial pH resulted in an increase in ions uptake. These results showed that immobilized algal cells in alginate beads could potentially enhance the biosorption of considered metal ions than freely suspended cells. Moreover, the biosorbent has significantly removed lead ions from municipal wastewater at the optimized condition. Immobilized algae in alginate beads were more effective than free cells. Consistently high ions removal was achieved. [ABSTRACT FROM AUTHOR]

The study was conducted to use different microbial species isolated from low-level radioactive wastewaters (up to 2 mSv) for removing non-radioactive (Co(II)) and radioactive cobalt (Cobalt-60) from waste solutions using different immobilization techniques; beads and thin film. Simple and innovate technique was used to prepare calcium alginate thin film. The isolated bacterial species investigated were Bacillus haynesii and Bacillus aerius while fungal species were; Aspergillus foetidus, Aspergillus parasiticus, and Penicillium oxalicum. The bacterial species were immobilized in wet form, while the fungal species were immobilized in wet and dry forms using sodium alginate gel. Screening of bacterial and fungal species in free and immobilized shapes for Co(II) and Cobalt-60 removal percent and capacity was studied. Moreover, the efficient immobilized weight could be used in the different immobilization shapes was investigated. Batch experiments were used to determine the optimum environmental conditions for cobalt removal by the immobilized beads or thin film. Scanning electron microscopy was done to observe the surface changes. However, the energy-dispersive X-ray analysis results indicated the accumulation of cobalt ions on the surface. The immobilized dry P. oxalicum beads showed higher Cobalt-60 removal percent about 79.3% as compared to all other immobilized bacteria and fungi biomasses. The statistical analysis using Statistical Package of Social Science (SPSS) indicated that the studied bacterial species had significant high means with (p-value < 0.05) for the removal efficiency either free or immobilized than studied fungal species. Also, there was a significant high means for immobilization in thin film shape than immobilization in beads for removal of Co(II) in both bacteria and fungi. In contrast, the immobilized beads had a significant high mean for Cobalt-60 removal in both bacteria and fungi. [ABSTRACT FROM AUTHOR]

Struvite crystallization for low-concentration ammonium wastewater provides a promising yet challenging way to recover nitrogen from bulk municipal wastewater. This research focused on the direct removal of low-concentration NH4+-N by fluidized bed reactor (FBR) with induced crystallization. NH4+-N (30 mg/L) was efficiently removed and Mg2+ and PO43- were employed as the precipitation reagents. The maximum of 82.0% NH4+ was removed when the pH was 10 and the stoichiometric ratio of [NH4+]:[PO43-]:[Mg2+] was 1:1.1:1. The rank of the influences of the three single factors on NH4+-N removal efficiency (%) was pH > P:N > Mg:N. The crystals achieved under optimal conditions were mainly struvite, while the addition of excess phosphate (N:P = 1:1.5) promoted the formation of crystals clusters instead of maintaining the typical orthorhombic structure, until Mg3(PO4)2·22H2O formed with an N:P ratio of 1:1.625. As most previous studies mainly focused on high-strength wastewater, this research demonstrated the potential of induced struvite crystallization by FBR for nitrogen recovery from low-strength ammonium wastewater treatment. [ABSTRACT FROM AUTHOR]

Wastewaters and agricultural sludges can contain high concentrations of phosphate and ammoniumor nitrate–nitrogen, which run off easily to waterways causing eutrophication in water bodies. However, it is possible to precipitate phosphate and ammonium as struvite and use it as recycled fertilizer. In this research, MgSO4 solution obtained by treating fly ash (FA) or dolomite (DOL) with sulfuric acid was used as a precipitant for simultaneous phosphorus and nitrogen removal from synthetic (NH4)2 HPO4 solution. Precipitation experiments were performed at room temperature (20°C ± 2°C) using different molar ratios Mg:P:N (1.1-2:1-2:1-2) and precipitation times (4–24 h). The pH was adjusted to 9.0 and kept constant. In all cases, there were only minor changes in the removal of both ammonium and phosphate after 4 h of reaction time. Highest ammonium removal percentages after the 4 h test were 79.5% for MgSO4 1.3:1:1, DOL 1.1:1:1, and DOL 1.3:1:1. Highest ammonium removal percentages (75.5%) for FA based MgSO4 solution were achieved using molar ratios Mg:P:N 2:1:1 and 1.1:2:2. Also, the highest phosphate removal percentages were achieved with these samples (97% for MgSO4 1.3:1:1, 93.3% for DOL 1.3:1:1, 89.8% for DOL 1.1:1:1, 84.5% for FA 2:1:1, and 82.5% for FA 1.1:2:2) Struvite was the only formed precipitation product in all cases as was confirmed by X-ray diffraction. Results indicate that fly ash and DOL based MgSO4 solutions performed quite well compared to commercial MgSO4 salt and they have great potential in the ammonium and phosphate precipitation. [ABSTRACT FROM AUTHOR]

In this study, the potential of alum sludge, obtained from a drinking water treatment plant located in Istanbul, Turkey, as an adsorbent for the removal of phosphate from aqueous solution was investigated. The effects of adsorbent amount, pH, initial concentration, and temperature on phosphate removal were studied by batch adsorption experiments. Equilibrium data were analyzed according to the Langmuir and the Freundlich isotherms. The Freundlich isotherm equation provided a better fit than the Langmuir isotherm equation. Thermodynamic parameters (ÄG, ÄH, and ÄS) related to the process were also calculated and reported. The positive value of ÄH and ÄS indicated the endothermic nature of the phosphate adsorption and the affinity of the adsorbent for the phosphate, respectively. [ABSTRACT FROM AUTHOR]

Cassava (Manihot esculenta) being rich in starch is one of the critical industries in the agro-industrial sector. The present study aims to do a comparative study on the treatment of cassava wastewater using biological and eco-friendly treatment approaches consisting of native bacterial species and fungal consortium in free, immobilized and biofilm batch mode. Studies were performed using the mixed culture of native bacteria, and the results were compared with that of a mixed fungal consortium of Trichoderma harzianum and Trichoderma viride which were known for its cyanide degrading efficiency and reducing COD burden. Cyanide and COD were two critical pollutants for the study. The effect of treatment time on cyanide and COD removal was investigated without adding any buffer to the wastewater. The maximum cyanide and COD removal efficiency for wastewater by using mixed native bacterial were 41.12% and 53.07% respectively. The removal efficiency by mixed bacterial culture was not too high owing to the low pH of cassava wastewater. Even in the low pH of cassava wastewater the maximum cyanide and COD removal efficiency using fungal consortium were 63.77% and 74.3% respectively. The growth pattern of fungal consortium reveals that six days treatment period showed maximum biomass of 3.721 g/L of dry weight. Thus, six days of treatment of fungal consortium can be used for the treatment of cassava wastewater. Furthermore, the optimized value of temperature and inoculums dosage for fungal consortium was found to be 30°C and 4% (v/v) of wastewater. Under optimized condition free, immobilized and biofilm batch reactors were setup. Biofilm batch reactor gave COD removal efficiency of 88% followed by suspension with 83.5% and least in an immobilized batch reactor with 76.5%. Cyanide removal efficiencies of 98.19%, 77%, and 87% were obtained in a biofilm, suspension and immobilized system respectively. The experimental results showed that final pH after treatment in all three systems was in dischargeable limits. The study revealed that the biofilm batch reactor which gave the highest removal efficiency could be considered as the best method for treatment of cassava wastewater. [ABSTRACT FROM AUTHOR]

The present investigation offers the scope for the elimination of glycosaminoglycans (GAGs), the amino sugars, present in tannery saline wastewater (also known as soak liquor) generated during the soaking of raw materials for the removal of common salt. The extracted salt tolerant amylase from Providencia Rettgerri sp., had very high amylase activity, 1320 U/ml. The modified NPAC(m-NPAC) was effectively produced by covalent incorporation method using ethylenediamine/glutaraldehyde for the immobilisation of amylase. The salt tolerant amylase immobilised nanoporous activated carbon (Am-NPAC) was used for the elimination of GAGs from soak liquor having chlorides of 4-5% (w/v). Various factors such as time, 120 min; pH, 6; temperature, 30°C; amylase concentration, 250 Units/g of m-NPAC and salinity, 3-5% of the medium that favour the maximum immobilisation of amylase onto m-NPAC were optimized. The instrumental techniques such as FT-IR spectroscopy, TGA-DSC, SEM and XRD analyses have confirmed the immobilisation of amylase. The optimum conditions such as time, 1 h; pH, 6; and temperature, 40°C for the elimination of GAGs from soak liquor were investigated. The amylase immobilised nanoporous carbon matrix (Am-NPAC) was very effective for the cleavage of GAGs into glucuronic acid and glucosamine bio-molecules. The removal of GAGs was confirmed through FT-IR, UV-visible and fluorescence spectroscopies. [ABSTRACT FROM AUTHOR]

Sewage treatments are introduced in the country to protect the health of human and environment. In this study, palm oil fuel ash (POFA) was explored as an adsorbent media for the treatment of a sewage wastewater. The optimum shaking speed, shaking time, pH, and dosage for chemical oxygen demand (COD), ammonia nitrogen, nitrate and phosphorus removal were investigated using the adsorbent media of particle sizes ranging from 2.00 to 3.15 mm. POFA and composite POFA chemical composition and characteristics were then determined. Results indicated that sewage concentrations of COD (63.39 mg L-1), ammonia nitrogen (6.01 mg L-1), nitrate (0.63 mg L-1) and phosphorus (0.43 mg L-1). The optimum conditions for shaking were determined at 200 rpm according to the adsorption of COD, ammonia nitrogen, nitrate and phosphorus by the media. Optimum shaking time of 20 min for ammonia nitrogen, nitrate phosphorus and COD optimum shaking time is 30 min. The optimum pH value for COD, nitrate and phosphorus removal using composite POFA was obtained at pH 6 and for ammonia nitrogen is pH 9. Microstructures of the prepared composite POFA were analyzed using Brunauer-Emmett-Teller, scanning electron microscope, X-ray diffractometer and X-ray fluorescence measurements. These results suggest that composite POFA can be used as a potential effective, low cost and eco-friendly green adsorbent for the removal of COD, ammonia nitrogen, nitrate and phosphorus from sewage wastewater. [ABSTRACT FROM AUTHOR]

Struvite precipitation is a well-known problem in wastewater treatment plants (WWTPs) as it causes clogging in pumps and pipes. However, controlled struvite recovery from sewage sludge can reduce these problems. The special feature of the present study is the pilot-scale reactor applied to study the efficiency of the designed system in struvite recovery from anaerobic sludge supernatant produced at Al Samra WWTP in Jordan. Moreover, various operational parameters effects on struvite formation have been investigated. By adjusting the pH value between 8.5 and 9, the efficiency of phosphorus removal achieved from experimental runs reached about 77%. Best efficiencies were obtained at high mixing speed (300 rpm), low mixing time (0.5 h) and settling time in the range of 8-16 h. Efficiency was found to be directly proportional to mixing speed and inversely proportional to mixing time and settling time. Struvite formation was verified by X-ray diffraction tests. [ABSTRACT FROM AUTHOR]

Biofilm in-situ sludge reduction process can reduce the yield of excess sludge and restrict biological phosphorus removal efficiency. In this study, a novel in-situ sludge reduction coupled side-stream induced crystallizing (SIC) phosphorus removal process was proposed. The feasibility of simultaneous high efficiency in-situ sludge reduction and removal of nutrients from domestic sewage, and SIC phosphorus removal potential were investigated. The results showed that operation effect of A²O-SIC was excellent with anaerobic supernatant side-stream flow ratio 40%, and pH 8, reaction time 30 min, seed size 100-150 mesh, aeration volume 300 L/h, Ca/P ratio 2.5, and seed dosage of 50% in SIC. The γobs of A²O-SIC was 0.18±0.05 g MLSS/g COD reducing 18.18% excess sludge than A²O sludge reduction process. The average concentration of effluent TP was 0.54 mg·L-1, and the removal rate was 88.89%. SIC does not affect the microbial activity of the biological system, whereas Ca2+ in the reflux liquid can promote the production of extracellular polymer and consequently, the formation of biofilm. Energy dispersive spectrometer test found that the proportion of P element on the seed crystal surface was significantly increased. In addition, the anaerobic area dominant species were Thauera, Methyloversatilis in the A²O-SIC and biological phosphorus removal was not inhibited. The experimental results provide an effective solution for simultaneous high-efficiency in-situ sludge reduction and phosphorus removal in wastewater treatment. [ABSTRACT FROM AUTHOR]

The discharge of phosphorus into surface waters results in overgrowth of aquatic plants and consequent eutrophication of rivers and seawaters; thus, removing this material to prevent surface-water nutrient uptake has received researchers’ attention in recent years. The aim of the present study was to investigate the efficiency of stabilization of zeolite nanoparticles modified by cationic surfactant on pumice aggregates to remove phosphate from aquatic environments. In this study, zeolite nanoparticles, modified by CTAB surfactant, were stabilized on pumice aggregates substrate using heating operation; then, the structural and physical features of the prepared absorbent were analyzed using FTIR, XRD, SEM, and EDAX techniques. Experiments were designed using Box-Behnken response surface methodology to improve the variables. Variables of pH (5–9), temperature (15–45°C), and amount of absorbent (5–15 g/L) were investigated. In addition, in order to investigate kinetics and adsorption isotherm, separate tests were conducted to determine the optimal amount of contact time (5–150 min) and phosphate concentration (5–28 mg/L). Results show that the optimum conditions to remove phosphate by modified aggregates were measured at a pH of 5; temperature of 45°C and absorbent amount of 15 g/L. Kinetics investigations showed that phosphate removal follows the second-order model and the optimum contact time was measured at 60 min in which phosphate removal efficiency was 82.22%. The results also show that phosphate adsorption isotherm has good agreement with Langmuir isotherm. The study shows that stabilizing the modified zeolite nanoparticles using cationic surfactant on pumice aggregate is highly effective for phosphate removal, thus it can be used for removing such pollutants from aquatic environment. [ABSTRACT FROM AUTHOR]

Phosphate in a water act as a primary nutrient for the algae and water bodies present in that water. This present phosphate is also responsible for the excess growth of algae through eutrophication in stationary water. High level of phosphate reduces the oxygen present in the water. Reduced oxygen is indirectly harmful to aquatic life present in the water. Excessive growth of algae can be reduced by removing the phosphate from water. Coal based fly ash (CFA) using adsorption method proved itself best technique for the removal of phosaphate from water. Oxides of aluminum iron and calcium in CFA is responsible for the phosphate adsorption from water. In this research work laboratory scale experiments were carried out using (CFA) and Modified coal based fly ash (MCFA). An effect of adsorbent concentration, contact time, pH and temperature were investigated for the phosphate removal from water. [ABSTRACT FROM AUTHOR]

The fabrication of mixed matrix membranes (MMMs) is a promising method to improve the properties of polymer membrane. In this study, composite polysulfone (PSf) membrane was prepared by blending Fe3O4 nanoparticles (NPs) via non-solvent induced phase separation (NIPS) method. The as-prepared Fe3O4/PSf membranes with different Fe3O4 loadings (60% and 120%) were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The membrane porosity, pore size, water flux, water contact angle, and bovine serum albumin (BSA) rejection were also analyzed. The presence of Fe3O4 NPs accelerated the phase inversion kinetics;therefore, membranes with opener finger-like structure and higher porosity were obtained. The Fe3O4/PSf membranes also demonstrated remarkable fouling resistance. When a 0.3 g·L-1 BSA solution was used as feed, the stable flux after 2 h filtration markedly increased by over 20 times compared to the pristine PSf membrane. Batch adsorption tests indicated that the composite membranes can effectively remove phosphate at pH ranging from 4 to 8. The adsorption kinetics can be fitted by both pseudo-first order and pseudo-second order models with correlation coefficients higher than 0.96. Intra-particle diffusion was not the rate-limiting step in the whole adsorption process. The maximum adsorption capacity obtained by Langmuir isotherm was 0.684 mg-P·g-1 for 120% Fe3O4/PSf membrane. In addition, the phosphate adsorption capability of the proposed Fe3O4/PSf membrane can be well recovered after regeneration using a 0.01 mol·L-1 NaOH solution. [ABSTRACT FROM AUTHOR]

Modern industrial waste waters often contain high concentrations of phosphate, and many methods have been explored to aid in its removal. This study investigates the use of magnetic nanoparticles as an adsorbent for phosphate removal. Aluminum-doped magnetic nanoparticles were synthesized using a co-precipitation method. Structure and composition analysis of the prepared magnetic nanoparticles indicated an inverse spinal structure with a composition of FeAl0.75 Fe1.25O4. These nanoparticles were tested for their phosphate removal properties, including adsorption capacity, selectivity, and kinetic models. They showed great affinity to phosphate with a maximum adsorption capacity of 102 mg/g. Additionally, the adsorption was selective, and the presence of other common anions and organic matters did not interfere with the phosphate adsorption efficacy. The kinetic analysis of phosphate adsorption suggested a pseudo-second-order adsorption behavior, and the adsorption isotherm studies indicated a Langmuir type adsorption. The phosphate removal capabilities of the nanoparticles were also tested in poultry rinsing water, tap water, and municipal wastewaters, all with high phos - phate removal efficiency. The overall results from these experiments showed promising results for the phosphate removal efficacy of these nanoparticles. [ABSTRACT FROM AUTHOR]

Although struvite crystallization has been proven an effective process to recover nutrients from wastewater, this method has not been used widely because of the cost of the raw chemicals, such as magnesium chloride, required as supplements. In this study, in view of the high cost of supplementing magnesium, reject water from a seawater reverse osmosis process was investigated as a potential source of magnesium. The magnesium was used in the nutrient recovery process, by which struvite crystallization was performed from the anaerobically digested effluent of swine wastewater. The results of all the experiments were positive, indicating that struvite formation was successfully performed from the effluent, using the concentrate water as a magnesium source. Removal efficiencies of up to 94.5% for phosphate and 12.7% for ammonium were achieved under normal operating conditions. Seed materials were successfully used as nucleation sites to enhance the purity of the struvite and the crystal size. The removal efficiencies of phosphate and ammonia could be improved up to 97 and 84%, respectively, by adding phosphate and seed materials. [ABSTRACT FROM PUBLISHER]

Electrochemical removal of scale-forming ions from hard water is based on the generation of a high-pH environment around the cathode. Although the possibility of electrochemical scale removal has long been recognized, industrial application of this technique is rather restricted. Limitations of the conventional electroprecipitation technology are the high cathode area requirement, the existence of a limiting current density beyond which the precipitation rate remains unchanged and the cumbersome need for periodic cleaning of the cathode surface. A novel electrochemical technique overcomes the above limitations. In conventional equipment, the cathode performs two functions: it generates alkalinity on the boundary layer in immediate contact with the electrode and also serves as a scale deposition surface. The basic concept of the electrochemical cation-exchange system (ECM system) is locating the anode and cathode in two cells separated by a cation-exchange membrane. In this case, a high-alkaline environment is generated throughout the whole volume of the cathode compartment. By transferring the alkaline solution to a separate crystallization vessel containing seeds of the precipitating species, the crystal deposition surface is now the extensive area of the seeds rather than the restricted area of the cathode. The aim of the present paper is to review performance data and capabilities of the ECM technology. The order of magnitude reduction in cathode area requirement is illustrated by CaCO3scale precipitation data. Further improvement of the ECM technology by integration of bipolar membranes is shown to provide higher energy efficiencies and to enable complete prevention of the undesirable process of chlorine generation. Application of the ECM technique for phosphate removal from secondary treatment effluent containing calcium and magnesium hardness is described. Finally, the ECM technique is shown to have a high potential for the removal of heavy metals from industrial wastewaters. [ABSTRACT FROM PUBLISHER]

The performance of a bench-scale anaerobic immersed membrane bioreactor (AnIMBR) when treating synthetic dairy wastewater was investigated. The investigation was carried out at mixed liquor suspended solid (MLSS) concentrations of 5,000, 1,0000, and 1,5000 mg/l and influent chemical oxygen demand (COD) concentrations of 2,000, 4,000, 6,000, and 8,000 mg/l. In order to avoid frequent membrane fouling, the investigation was conducted at permeate flux of about 2.2 l/m2h. Results of the investigation showed that maximum removal efficiencies of COD (91.4 percent) and turbidity (99.4 percent) were achieved at MLSS and influent COD values of 15,000 and 4,000 mg/l, and 15,000 and 2,000 mg/l, respectively. A maximum biogas yield of 0.17 l/g CODrwith methane content of 82 percent was obtained at an MLSS value of 15,000 mg/l. Mathematical relationships between daily biogas production and MLSS and influent COD concentrations were formulated. Throughout the investigation, sludge production was at an average of 0.022 mg VSS/mg CODr. Results of the investigation also showed that total phosphate could be removed by more than 86 percent, which was achieved at an MLSS value of 5,000 mg/l. [ABSTRACT FROM AUTHOR]

In this study, phosphate (P) removal from aqueous solutions by hydrocalumite was investigated using batch experiments and model analyses. The maximum phosphate removal capacity was determined to be 127.53 mg P/g under the given experimental conditions (hydrocalumite dose = 0.05 g/L, initial P concentration = 2–20 mg P/L, reaction time = 24 h). Model analyses showed that the Elovich model was most suitable for describing the kinetic data, whereas the Redlich–Peterson model provided the best fits to the equilibrium data. Furthermore, phosphate removal by hydrocalumite was not sensitive to pH changes between 4.0 and 11.0. A thermodynamic analysis indicated that phosphate removal by hydrocalumite increased with a rise in temperature from 15 to 45°C, suggesting that the removal process was spontaneous and endothermic (ΔH° = 32.05 kJ/mol, ΔS° = 112.86 J/K/mol, ΔG° = −0.47 to −3.86 kJ/mol). The phosphate removal capacity in stream water (5.40–17.25 mg P/g) was also lower than that in a synthetic P solution (6.86–27.51 mg P/g) under the given experimental conditions (initial P concentration = 2 mg P/L, hydrocalumite dose = 0.05–0.3 g/L, reaction time = 24 h). Such a result could possibly be ascribed to the presence of carbonate ions () in the stream water, which could interfere with phosphate removal by hydrocalumite through the precipitation of calcium carbonate (CaCO3). [ABSTRACT FROM PUBLISHER]

The use of low-cost and locally available material in the treatment of wastewater has recently become an issue of interest, and magnesite as a low-cost material has been used for the removal of heavy metals in wastewater and has also shown potential as an adsorbent for the removal of phosphates in wastewater. In this study, batch experiments were conducted to evaluate the effectiveness of cryptocrystalline magnesite in the removal of phosphates from wastewater. Parameters optimized include the following: contact time, dosage, ions concentration and pH. Optimum conditions were observed to be 60 min of agitation, 1 g of dosage, 100 mg L−1ions concentration, 1:100 S/L ratios and pH 10. The phosphate removal efficiency was found to be greater than 99% at an adsorption capacity of 20 mg g−1of magnesite under the optimized conditions. Adsorption kinetics fitted well to pseudo-second-order kinetics than pseudo-first-order kinetics with pore diffusion also acting as a major rate governing step, hence proving chemisorption. Adsorption isotherms fitted well to Langmuir adsorption isotherm than Freundlich adsorption isotherms, demonstrating monolayer adsorption. PHREEQC geochemical model showed Mg3(PO4)2and MgHPO4:3H2O as the phosphate-bearing mineral phases formed in the removal of phosphate. The optimized method is thus proposed for the application for phosphate removal from wastewater at household and municipal plant levels. [ABSTRACT FROM AUTHOR]

A ceramic membrane was prepared on SiO2support through suspended powder technology from cost-effective natural clay. The sintering temperature was selected at 600°C according to thermogravimetric analysis of the raw powder. Results of Fourier transform infrared spectroscopy and X-ray fluorescence (XRF) showed the natural clay had high physicochemical similarity to phyllosilicate. Crystal structure, pore size distribution, and effective membrane thickness of the natural clay membrane (NCM) were also studied. X-ray diffraction patterns revealed a phase conversion occurs during sintering. The results of mercury porosimetry showed the pore size distribution of NCM ranged from 3 to 10 nm. Scanning electron microscopy images showed NCM distributed uniformly on the support with an approximate thickness of 30 μm. The transport and separation performances of NCM were tested in batch mode through a stirred cell under dead-end mode. It was found that retention ofwas pH-dependent with the satisfactory rejection rate under alkaline conditions (pH > 10). The analysis of XRF made it reasonable to assume that amphoteric Al2O3in the raw material should be responsible for the effective retention through electrical-related interactions. In addition, both increasing temperature and applying turbulence affected the retention positively. Filtration resistance analysis of treating phosphate solutions indicated that irreversible fouling could be completely neglected, and concentration polarization was the main cause of reversible fouling. [ABSTRACT FROM PUBLISHER]

In this study, the sorption ability of nitrate containing MgAl layered double hydroxide as an anion-exchanger to remove phosphate from a real effluent was investigated. The LDH material was prepared via coprecipitation method and characterized by X-ray diffraction, SEM, Fourier Transform Infrared, BET surface area, and pHzpc. The effect of physico–chemical key parameters on phosphate removal, such as sorbent dosage, solution pH, initial concentration, and contact time, has been studied in batch mode. The sorption reached equilibrium within 30 min. Furthermore, the sorption mechanism of phosphate onto MgAl-NO3LDH is a combination of both anion-exchange and electrostatic attraction. The equilibrium 8 data were tested using Langmuir, Freundlich, and Dubinin–Radushkevich isotherms. The results show that the Langmuir isotherm describes sufficiently the sorption equilibrium, offering a maximum sorption capacity of 64.10 mg/g. Sorption kinetic follows accurately pseudo-second-order reaction. The sorbent reusability shows that regenerated LDH can be reused in subsequent sorption–regeneration cycles with a slight decrease in sorption capacity. [ABSTRACT FROM AUTHOR]

Removal of potentially harmful phosphorus compounds from wastewater by adsorption onto biosorbents is a cost-effective alternative to the conventional treatment methods. Raw peat and peat modified with iron(III) hydroxy ions were used in this study to remove phosphate ions from synthetic solution and household wastewater. Interaction of iron(III) ions with carboxylic groups of peat occurred during peat modification, which was confirmed by the FTIR technique. The effect of the initial phosphate concentration, pH, contact time, temperature, and ionic strength was studied in batch experiments. It was found that the sorption capacity increased with the increasing temperature, i.e. the maximum sorption capacity of the modified peat was 9.64 mg P/g at 2°C and 11.53 mg P/g at 40°C, respectively, indicating the endothermic nature of the sorption. Besides, the Langmuir equation was used to describe the sorption isotherms quantitatively. Given that the spent biosorbent did not exhibit phytotoxicity and the concentration of heavy metals did not exceed the limit values, the phosphate-saturated modified peat may be utilized as an organic fertilizer in agricultural land application. [ABSTRACT FROM AUTHOR]

This paper discusses two possible ways of intensifying the electrocoagulation treatment of water containing phosphate. The first one consists of controlling the chemical composition of the water by continuous adjustment of the pH. The second aspect focuses on electrode connection modes, and the four different modes were tested monopolar in series, in parallels and independents, and finally bipolar. Experiments were conducted in a small batch reactor containing water with 100 mg P/L using electrodes of aluminum. Several electrical connections were used for the water treatment under favorable operating conditions determined by a study and presented in a previous paper. The influence of pH adjustment was conducted using different adjustment step times (no adjustment, every 30, 10 and 5 min). The kinetics of the treatment was found to be accelerated by continuous adjustment of the pH. The choice of the electrode connection modes was found to strongly affect the efficiency of the treatment, the Faradic yield, and the consumption of energy. The monopolar in parallels connection mode was found to be the most economic, whereas bipolar in parallels was found to favor a higher kinetic rate of treatment. [ABSTRACT FROM AUTHOR]

In this study, the efficiency of alum sludge for removing phosphorus from synthetic and municipal wastewater (MWW) was investigated. Orthophosphorus (OP) and condensed phosphorus (CP) were used as model pollutants. Alum sludge (A and B) from two local treatment plants was collected, dewatered, dried, and processed before use. Batch experiments were performed to determine OP and CP removal under equilibrium conditions. Sludge dose, contact time, and pH were optimized for both sludges. Adsorption efficiencies of OP and CP were determined by using Langmuir and Freundlich adsorption isotherm models. The maximum adsorption capacity (Qo) for sludge A was found to be 4.86 mg/g for OP, and 4.21 mg/g for CP at 12 g/L of sludge dose, 90 min of contact time, and pH 4. For sludge B,Qowas 1.58 mg/g for OP and 4.71 mg/g for CP at 30 g/L of sludge dose, 80 min of contact time, and pH of 5.5. Results showed that pH of wastewater significantly affected adsorption capacity and better removal was achieved within pH range of 4.0–5.5. Optimized conditions for sludge A and B were applied on MWW which provided over 90% of OP and 70–80% of CP removal. Sludge B performed better than sludge A in case of domestic wastewater. This study concluded that alum sludge as being a great resource for phosphorus removal from wastewater, and could be applied to streams feeding water supply reservoirs for prolonged oligotrophic conditions. [ABSTRACT FROM AUTHOR]

Jordanian phosphate mine wastes (PMW) at Ruseifa City was fully characterized and tested for its PO4removal capacity by batch experiments using prepared phosphate solutions and domestic wastewater. PMW particles are positively charged with median particle size of 0.625 μm. Mineralogical and chemical analyses of PMW showed that it is mainly composed of calcite, fluorapatite, and quartz with high concentrations of calcium and phosphorous. The phosphate concentrations in PMW range from 11 to 24% expressed as P2O5. PMW as a sorbent has a very high PO4removal efficiency from wastewater and prepared solutions. PO4solutions with concentrations ranging from 5 to 5,000 mg L−1were prepared and utilized in batch experiments in the presence of PMW as a sorbent. The concentration of PO4in the solution phase and pH were the main parameters influencing the PMW sorption capacity of PO4. The PO4removal efficiency from prepared solutions was up to 99%. Moreover, Langmuir sorption model was able to describe the observed data for PO4sorption by PMW. The sorption data at PO4concentrations >50 mg L−1were highly fitted to Langmuir model. The estimated sorption maximum capacity (bmax) of PMW was 46,620 mg kg−1. On the other hand, domestic wastewater samples obtained from six Jordanian wastewater treatment plants were subjected to PO4removal by PMW, and the results showed that the PO4removal efficiency exceeded 97%. The adverse environmental impacts and human health risks associated with PMW presence are briefly discussed. [ABSTRACT FROM PUBLISHER]

An anaerobic–anoxic/nitrifying-induced crystallization sequence batch reactor (A2N-IC-SBR) process was developed for enhanced nutrient removal and phosphorus recovery. The performance of the A2N-IC-SBR process was investigated in this study. Compared to the A2N-IC continuous flow (CF) process, A2N-IC-SBR provided important advantages, including minimal space requirements, ease of enhanced phosphorus recovery, and improved ammonia removal. Percentage of chemical phosphorus removal of total phosphorus removal was 14.9–17.1% in the A2N-IC-SBR process, while it was 8.0–12.6% in the A2N-IC-CF. The effluent ammonia concentrations were below 5 mg/L. The A2N-IC-SBR process met the requirements of Urban Waste Water Treatment Directive 91/271/EEC. Furthermore, ammonia and nitrate concentrations could be simulated satisfactorily in each stage. In addition, an important feature called the self-adjustment characteristic was found, as the system has the ability to cushion the effect of increased or decreased chemical phosphorus removal amount during the process. [ABSTRACT FROM PUBLISHER]

Surface modification can improve biochar adsorption capacity. Biochars were produced from wheat straw through low-temperature pyrolysis at approximately 450°C, activated with hydrochloric acid (HCl), and coated with iron (FeCl36H2O) of different amounts. Results showed that activation with HCl and coating with iron can significantly increase biochar adsorption capacity. The increase after HCl treatment was very small at a high ratio of iron to biochar. The optimal ratio of iron to biochar for iron-coated biochar was 0.70. Adsorption capacity was calculated based on the amount of pure nitrogen or phosphorus. The maximum adsorption capacities were 2.47 and 16.58 mg g−1. The most effective pH values for nitrate and phosphate removal were 3 and 6, respectively. The active substance of the optimal-modified biochar (OMB) was amorphous FeOOH, and the structurewas the hydroxylated mineral surface of OMB in a water solution. The equilibrium pH of the adsorption solution was lower than 7 even when the initial pH of the solution was 11 becausechanged into,, and H3O+with the increase in pH. Adsorption experiments showed that OMB can be utilized to remove nitrate and phosphate from water. [ABSTRACT FROM PUBLISHER]

A seeding concept was successfully applied for water treatment application, in particular to phosphate removal from wastewater. Here, several different seeding materials based on hydroxylapatite and fluoroapatite were synthesized and the P-removal capabilities were tested in a test water system. Besides high chemical stability, the fluoroapatite seeding material successfully and repeatedly removes >95% of phosphorous from the test water. A small pilot test was carried out, showing that also in continuous operation the seeds have high removal capacity of >90%. [ABSTRACT FROM PUBLISHER]

An innovative process step-feed Anaerobic-multiple Anoxic/Oxic-Membrane Bioreactor [An-M(A/O)-MBR] was developed for biological phosphorus and nitrogen removal from synthetic domestic wastewater. This process was composed of an anaerobic reactor, a multiple phases of aerobic and anoxic zones (multiple A/O zone) in sequence followed by a continuous aerated MBR. Performance of the laboratory-scale system was investigated at different organic compounds in the influent. The results showed that, under the conditions imposed, although the Chemical Oxygen Demand (COD) concentration fluctuated in the range of 120–1,200 mg/L, high performance on COD removal was achieved in the system and more than 95% removal efficiency was obtained throughout the operation, the COD concentrations in the effluent were lower than 50 mg/L throughout the operation. However, COD levels in the influent had great influence on nitrogen and phosphorus removal. When COD level was low (120–200 mg/L), poor performance of nitrogen and phosphorus removal were obtained because of carbon source deficiency. Good performance on total nitrogen (TN) and total phosphorus (TP) removal were achieved when COD level was in the range of 350–710 mg/L, and the average removal efficiency of TN and TP was above 85 and 84%, respectively. But when COD increased to a high level (1,110–1,200 mg/L), the performance of nitrogen and phosphorus removal also deteriorated possibly because of the shift of the composition of the microbial communities. [ABSTRACT FROM PUBLISHER]

Nitrate-intercalated layered double hydroxides (LDHs) were prepared and assessed for phosphate removal from water. The sorption experiments for phosphate uptake were carried out as a function of LDHs’ dose, contact time, initial pH of solution and initial phosphate concentration. The results show that about 97–99% phosphate removal was achieved at dose 0.3 g/L for the 10 mg-P/L test solution by Ca-based LDHs. The adsorption data fitted well with Langmuir isotherm and the maximum sorption capacity can be up to 70.9 mg-P/g of adsorbent. All selected Ca-based LDHs were observed to have a strong buffering capacity, indicating the suitability of potential application under different pH systems. The results also demonstrated that the real effluent from a wastewater treatment plant with high P content (3.4–10.4 mg/L) can be treated by Ca–Al-60 LDH with more than 90% P removal. [ABSTRACT FROM PUBLISHER]

In the laboratory-scale research, anoxic membrane bioreactor (MBR), in which a membrane is submerged in the second anoxic reactor, and aerobic MBR, where a membrane is installed in the aerobic reactor, were operated simultaneously to observe advantages and disadvantages of the 4-stage anoxic MBR process. The advantages observed were as follows: (1) nitrogen concentration in effluent (5.2 mg N/L) superior to that in aerobic MBR (7.1 mg N/L) and (2) efficient utilization of carbon source to remove nutrients (2.46 g SCODutilized/g [Ndenitrified + Preleased]). In contrast, the disadvantages of this process were as follows: (1) relatively higher phosphorus concentration in effluent (0.9 mg/L) than in aerobic MBR (0.5 mg P/L), (2) 20% lower membrane permeability, and (3) 25% lower sludge settleability. [ABSTRACT FROM PUBLISHER]

A low-grade iron ore with phosphorus (LGIOWP), the extensive industrial solid waste generated in mining of high phosphorus iron ore, was investigated to assess the effectiveness for the removal of phosphate from aqueous solution. The factors influencing the adsorption were examined, and the related adsorption mechanism was discussed. The results showed that pH value had a significant effect on the phosphate removal. The optimum pH value for phosphate adsorption was 5.6. The adsorption of phosphate mainly on hematite ligand exchange is likely the key mechanism for phosphate removal when pH is in the range of 1−9. When pH value was above 9, the presence of dolomite played an important role in phosphate removal. The adsorption capacity is enhanced with a higher initial phosphate concentration. Kinetic studies show that the adsorption follow pseudo-second-order kinetic model. Langmuir and Freundlich isotherms were used to simulate the adsorption equilibrium data. The adsorption fits well with the Langmuir isotherm model and the maximum adsorption capacity is found to be 11.44 mg/g. Due to possessing the low cost and high capability, LGIOWP could be a promising material for phosphate removal in the wastewater treatment. [ABSTRACT FROM PUBLISHER]

Phosphorus in the effluents from decentralized septic tanks in the northeastern US imposes the threat of eutrophication on the sensitive receiving water bodies. Dissimilar to the popular nutrient-removal processes used in the wastewater-treatment plants, a lab-scale septic system retrofitted by iron amendment was developed in this study to stimulate phosphate precipitation in septic tanks. These results demonstrate that iron supplementation can effectively remove aqueous phosphorus in the septic system. In a stabilized anaerobic sequencing batch reactor (ASBR), more than 96% of the phosphorus was removed when iron was added at an Fe/P (molar ratio of Fe(III) addition to aqueous P) of 3. The iron demand for phosphorus precipitation in batch assays was considerably higher (an Fe/P ratio of 10 to achieve a phosphorus removal of 94.5%), indicating the presence of additional pathways for Fe(II) consumption, which was most likely due to the accumulation of extra Fe(II) consumers in the septic materials sampled. The removal of the soluble chemical oxygen demand in the ASBR was improved by 21–44% when the Fe/P ratio was increased from 1.5 to 3, suggesting that organic carbon was used as an electron donor for iron reduction; therefore, carbon mineralization was enhanced. Analysis of X-ray diffraction, electron microscopy, and energy dispersive X-ray spectroscopy show that vivianite was the main secondary mineral resulting from the iron reduction in the septic system. [ABSTRACT FROM PUBLISHER]

Pine bark (PB) wood residues were chemically modified and used as anion exchange resins to remove phosphate (PO) from water. The modification process involved reacting a choline-based ionic liquid analog, comprised of a mixture of choline chloride derivative and urea, with natural PB in the presence of imidazole. Batch sorption tests showed that the modified PB has a maximum PO–P uptake capacity of 2.09 mmol/g (64.8 mg g−1). The changes at the surface of the PB due to chemical modification and phosphate uptake were monitored using Fourier transform infrared spectroscopy analysis and Zeta potential measurements. The adsorption was found to be concentration and ionic strength dependent, exothermic, spontaneous, and is best described by a pseudo-second-order kinetics. The modified residues were used for the removal of POfrom an effluent of a dairy farm anaerobic digester and from a wastewater treatment plant sludge centrate. [ABSTRACT FROM PUBLISHER]

Chitosan beads cross-linked with glutaraldehyde were loaded with Zn(II) for the removal of nitrate and phosphate. The Zn(II) was bound by the free amino groups in the cross-linked chitosan beads. In order to utilise the hydroxyl groups on cross-linked chitosan, it was carboxylated with chloroacetic acid and then loaded with Zn(II). Both the sorbents viz. zinc-loaded cross-linked chitosan beads (ZnCB) and zinc-loaded carboxylated cross-linked chitosan beads (ZnCCB) were characterised by SEM, EDAX, X-ray diffraction and FT-IR. Adsorption studies were carried out in batch mode. The maximum adsorption capacity of ZnCB and ZnCCB for nitrate was 27.56 and 59.00 mg/g, respectively and for phosphate it was 31.45 and 67.50 mg/g, respectively. The suitability of the Freundlich, Langmuir and Dubinin–Radushkevich adsorption models to the adsorption equilibrium data was investigated. The equilibrium data obtained for nitrate and phosphate removal using ZnCCB were found to follow Freundlich adsorption isotherm. The thermodynamic parameters were evaluated. The results showed that the adsorption process was spontaneous, endothermic and entropy driven. [ABSTRACT FROM PUBLISHER]

Granular ZnAl layered double hydroxides (LDHs) were prepared to study the possible application of the material in phosphate removal from secondary effluents in wastewater treatment plants. The structural and phosphate adsorption properties of LDHs granules were compared with those of powder LDHs. The results of powder X-ray diffraction and Fourier transform infrared spectra show that polyvinyl alcohol as a binding agent did not change the interlayer distance of ZnAl LDHs or interact with the hydroxyl layers or interlayer anions. Although the distribution of pore size in granular ZnAl LDHs was similar to that in powder samples, the total pore volume and Brunauer–Emmett–Teller specific surface area decreased by 68.2% and 63.1%, respectively, after granulation. The phosphate adsorption capacity of granular ZnAl LDHs was to some extent lowered compared with that of LDHs powder; nevertheless, the decrease was not proportional to the reduction in the specific surface area, suggesting that physical surface adsorption was not a major pathway of phosphate uptake by ZnAl LDHs. Phosphate adsorption onto ZnAl LDHs powder was basically a two-step process: a fast uptake in 1 h and a slower uptake afterward, which fit well to pseudo-first-order models and pseudo-second-order models, respectively. Phosphate uptake by granular LDHs, however, had better agreements with intra-particle diffusion models during the entire contact time, indicating that mass transfer became the rate-limiting step in phosphate adsorption after LDHs granulation. [ABSTRACT FROM PUBLISHER]

An aluminum iron-rich laterite with granular shape was developed as a phosphate absorbent candidate. Batch tests showed that phosphate sorption on the granular laterite (GL) was fitted well with the Langmuir and Freundlich models. The kinetics was the pseudo-second-order reaction. The physical characterization suggests that the adsorption and precipitation are responsible for P removal. Moreover, the adsorption of phosphate was highly pH dependent as high P removal amount was observed in the acidic solution. The presence of concomitant anions inhibited phosphate adsorption onto GL in the descending order of extent >  > . Column experiments were carried out under a constant bed depth at different influent concentrations, which demonstrated that the capacities of the exhaustion point decreased with the increase of the influent concentration. Based on the results above, GL doped with iron was prepared. According to the response surface methodology, a Box–Behnken design (BBD) was applied to give the optimized preparation conditions (quality percentage concentration of 43%, activation time of 2.13 h, and impregnation time of 0.5 h). The estimated phosphorus sorption capacity under the optimized conditions was 1.542 mg P/g, which was much higher than that using GL without modification. [ABSTRACT FROM PUBLISHER]

The present study was conducted to investigate the efficacy of red soil (RS), as a natural adsorbent, for phosphate removal from wastewater. The chemical composition of the adsorbent was determined by proton-induced X-ray emission and proton-inducedγ-ray emission methods. Apart from evaluating the influence of major experimental parameters, the equilibrium data were analyzed by different isotherm models and kinetic models. Experimentally obtained values, such as separation factor (RL), 0.0297, Freundlich exponent (n), 2.994, and Gibb’s free energy change (ΔG°), −1.279 kJ mol−1, suggest that the phosphate adsorption by RS was a favorable and spontaneous process. The presence of coexisting anions showed no competing effects on phosphate removal efficiency. For synthetic initial phosphate concentration of 20 mg L−1and contact time of 90 min, phosphate removal efficiency was 96.47% in batch mode and 19 h of breakthrough time in column mode. Whereas with real domestic wastewater having 5.62 mg L−1of initial phosphate concentration, removal efficiency was as high as 99.8% in batch mode and 70 h breakthrough time in column mode. The results of this study suggested that RS can be used as a low-cost and highly efficient adsorbent for phosphate removal from wastewater. [ABSTRACT FROM PUBLISHER]

The objective of this work was to assess the feasibility of biological phosphorus removal for dairy processing wastewater. In this study, two fixed-film systems carried out continuously were tested in the laboratory. The effect of aerobic and "anoxic/anaerobic/aerobic" conditions on phosphates removal has been investigated on both the fixed-film systems and reported, that alternating phase's system (bioreactor 1) resulted in higher phosphorus removals relating to aerobic system (bioreactor 2). The main results showed that the effectiveness of COD and phosphates for bioreactor 1 reached, respectively, to 66 and 91% at stable bio- film functioning. Similarly, the effectiveness of COD and phosphates removal for bioreactor 2 reached to 70 and 84.61%, respectively. No clogging of media occurred and no backwashing was applied on both the systems during the study. Also, kinetic analysis of the reactor with regard to phosphorus removal has been studied with the modified Stover-Kincannon kinetic model which was chosen for modeling studies and experimental data analysis of the fixed-film system used in this study. The experimental data showed that the Stover-Kincannon kinetic model was the most suitable for predicting the removal of phosphate in the bioreactor 1, but not in the bioreactor 2. [ABSTRACT FROM AUTHOR]

Treatment of industrial wastewater from Eshidiya phosphate mining in Jordan was studied in this work for reuse possibilities. The wastewater resulted from flotation cells contains sediments, mainly phosphate. Sedimentation and enhanced sedimentation using anionic polyelectrolyte and alum were used to remove the sediments. The optimum dosage of anionic polyelectrolyte was found to be 400ppm corresponding to a turbidity of 3.3 NTU. The measured target zeta potential was found to be -58.7mv at this dosage. Alum was found to be effective coagulant but after performing a preliminary sedimentation step to reduce the wastewater turbidity. [ABSTRACT FROM AUTHOR]

An innovative step-feed Anaerobic-(Oxic/Anoxic)"-Membrane Bioreactor [An-(O/A)"-MBR] process was developed to treat synthetic domestic wastewater. Performance of the lab-scale system was investigated at different dissolved oxygen (DO) concentration (0.4-2.4mg/L) in the aerobic tank of the multiple A/O zone. The results showed that, under the conditions imposed, the DO level has little influence on chemical oxygen demand removal and the removal efficiency was more than 94% throughout the operation. However, DO levels have great influence on nitrogen and phosphorus removal. Better nitrification efficiency could be obtained when DO was in the range of 0.8-2.4mg/L; the ammonia removal efficiency was more than 99%. High total nitrogen (TN) and total phosphorus (TP) removal performance can be obtained when DO was in the range of 0.8-1.2mg/L; the average removal efficiency was 74.8 and 71.4%, respectively. In this condition, DO can meet the demand of nitrification and phosphorus uptake simultaneously, and the simultaneous nitrification and denitrification occurred in the aerobic tanks under lower DO concentration. Meanwhile, since the DO circulated from the aerobic tank to the anoxic tank decreased, denitrification was enhanced and the nitrate quantities in the sludge recycle system decreased, resulting in the decrease of carbon substrate competition between denitrification and phosphorus release in the anaerobic zone. Ultimately, the performance of TN and TP removal was enhanced. [ABSTRACT FROM AUTHOR]

The multi-objective genetic algorithm (MOGA), aiming at determining the optimal set points for controllers existed in the supervisory control layer, is developed to enhance the treatment performance of a combined biological nitrogen and phosphorus removal wastewater treatment process (i.e. an anaerobic-anoxic-oxic process). Firstly, a cascade ammonia controller that consists of a primary proportional-integral (PI) controller and a secondary PI controller is set up and tuned using the internal model control tuning rule. The primary controller is used to control the ammonia concentration in the effluent and the secondary controller is used to control the dissolved oxygen concentration in the last reactor. This cascade controller could lead to better set point tracking and disturbance rejection control performance. Then, the multiobjective optimization (MOO) of the effluent ammonia controller set point and the nitrate controller set point in the fourth reactor is performed using the MOGA. The two conflicting optimization objectives are (1) effluent quality index which is a function of various main effluent loads and (2) energy consumption which is the sum of aeration energy consumption and pumping energy consumption. The MOO results indicate that the optimal set points for the effluent ammonia concentration and the nitrate concentration in the fourth reactor are both about 1.1 gN/m³. The cascade controller with the optimal set points has the capability of enhancing the effluent quality and the energy-saving performance simultaneously. [ABSTRACT FROM AUTHOR]

Profiles of chemical oxygen demand (COD), dissolved oxygen (DO), ammonia nitrogen (Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed.), nitrate nitrogen (NOx--N) and phosphorus (P) were established in a cycle of a four-phased Bio-Denipho process. Based on a unit-flow model and the ASM2d, organics degradation, nitrification and denitrification, and phosphorus removal processes were analysed. A switch function has been introduced to address the difference in DO concentrations between the core of biomass flocs and their outer-layers or the bulk suspensions. The calculations indicate that approximately 68% of the denitrification and nitrogen removal resulted from reactions within the anoxic cores of the biomass flocs, where DO was around 0.1 mg l-1 or less. This proved to be important mechanisms to phosphorus removal in the model for the four phased ditches. The analyses provide an insight in the nitrification, denitrification, and phosphorus removal mechanisms in such operation system, which is useful for the system diagnosis and optimisation. [ABSTRACT FROM AUTHOR]

The dynamic removal of different forms of dissolved and suspended phosphorus (reactive phosphorus, acid-hydrolyzable phosphorus, organic phosphorus and total phosphorus) by the cyanobacteria Aphanothece microscopica Nägeli cultivated heterotrophically in dairy processing wastewater was investigated. Bioreactor performance was highly dependent on operation temperature (10-30°C). Aphanothece microscopica Nägeli was able to uptake not only simple phosphorus species (reactive and acid-hydrolyzable phosphorus), but also complex fractions of organically bound phosphorus. Low bioreactor performance was evidenced by the suspended fractions. The conversion of suspended reactive phosphorus and suspended acid-hydrolyzable phosphorus varied between 50.3% and 93.3%. Suspended organic phosphorus and suspended total phosphorus became erratic, with peaks of phosphorus appearing after 8 h of hydraulic detention time and slightly impacting the global phosphorus balance. In addition to phosphorus removal, a good degree of organic matter and total nitrogen (N-TKN) removal occurred simultaneously. The resulting conversions varied from 64.6% to 96.9% and from 47.2% to 72.8% for chemical oxygen demand and N-TKN, respectively. Rapid biomass growth was verifi ed and the resulting biomass production rates were 0.81-3.85 g l-1 d-1. These results indicate that heterotrophic bioreactors with cyanobacteria have a good potential for phosphorus removal from wastewater. [ABSTRACT FROM AUTHOR]

The photocatalytic reduction of phosphorus in the acid pickling milling wastewater from high phosphorus hematite mineral processing was innovatively performed in the absence of oxygen and in the presence of hole scavenger under visible light irradiation with Sr-doped TiO2 in the study. Types and ratio of hole scavenger, effect of reduction time, dosage of Sr-doped TiO2 and initial phosphorus concentration on the reduction of phosphorus were investigated. Experimental results indicated that the gaseous product of the photocatalytic reduction was identified to be phosphine. The optimum amount of formic acid and TiO2 were 60 mmol l-1 and 2.0 g l-1, respectively, and the phosphorus removal could reach 99.96% when used to treat the actual mineral processing wastewater. The photocatalytic reduction of phosphorus could be described by first order kinetic equation, and the reaction rate was proportional to the concentration of reactants. [ABSTRACT FROM AUTHOR]

Phosphate removal from pickling milling wastewater of high-phosphate hematite mineral by in-situ self-formed dynamic membrane reactor (DMR) developed with raw and activated red mud (RM-raw and RM-a) was studied in this paper. The results indicated that RM dosage, velocity gradient of the mixer (G value), reaction time (t), and pH were main effects on phosphate removal. The pH of the actual mineral processing wastewater is 2.50-2.53 while the phosphate concentration is 98.85 mg/l. After the treatment, the removal rate of phosphorus with RM-raw and RM-a can reach 94.33% and 99.72%, respectively, with the dosage of 23.00 g/l and 20.00 g/l, respectively. Correspondly, effl uent pH was respectively 8.12 and 3.06, and both turbidity could reach the effl uent requirement. Brush cleaning was a very effective cleaning method, and the membrane fl ux of DMR could be restored. Also, it demonstrated that acid reuse from the phosphate-contained acidic wastewater from wastewater produced in high-phosphate hematite pickling process could be achieved by in-situ self-formed dynamic membrane technology. [ABSTRACT FROM AUTHOR]