Phosphate Removal Rate Research Articles

Removal-Regeneration of Aqueous Phosphate with Bulk and Thin-Layer Boehmite

The removal properties of aqueous phosphate with commercially available boehmite were compared with those with a corresponding compound prepared by the sol–gel method. It was found that the removal rate when using the prepared boehmite was evidently greater than that using the commercial reagent. The removal rate using the prepared boehmite was strongly influenced by the amount of acid added in the peptization step during the sol–gel preparation. As a development of the boehmite utilization, a glass plate was coated with boehmite and utilized for the removal and regeneration of aqueous phosphate. The removal rate of aqueous phosphate was dependent on the dip-coating times and the preparation method of the precursor sol. It was also described that the removed phosphate could be eluted from the coated plate with aqueous ammonium, suggesting that boehmite film can be employed for the continuous removal and regeneration of aqueous phosphate.

An ectophosphatase activity inCryptococcus neoformans

There is increasing evidence in the literature showing that fungal pathogens express biologically active ectoenzymes. The expression of surface phosphatases at the cell surface of Cryptococcus neoformans, the etiologic agent of cryptococcosis, was evaluated in the present study. Different isolates of C. neoformans express ectophosphatase activity, which is not influenced by capsule size or serotype. The cryptococcal enzyme is an acid phosphatase, inhibited by classic inhibitors of ectophosphatases, including ammonium molybdate and sodium salts of fluoride and orthovanadate. Only the inhibition of enzyme activity caused by sodium orthovanadate has been shown to be irreversible. The cryptococcal ectoenzyme is also inhibited by Zn2+ and inorganic phosphate, the final product of reactions catalyzed by phosphatases. The ectophosphatase from C. neoformans efficiently releases phosphate groups from different phosphorylated amino acids, giving a higher rate of phosphate removal when phosphothreonine is used as a substrate. Yeast cells with irreversibly inhibited ectophosphatases are less capable of adhering to animal epithelial cells than fungi fully expressing enzyme activity, suggesting that ectoenzyme expression can contribute to the pathogenesis of C. neoformans.

Treatment of nitrogen and phosphorus in highly concentrated effluent in SBR and SBBR processes

Various sludge treatment processes produced supernatant with high ammonia concentration from 500 to 2,000 mgN/L and generally high phosphate concentration. Conversion of ammonia into nitrite via partial nitrification has proven to be an economic way, reducing oxygen and external COD requirements during the nitrification/denitrification process. Two processes with biomass retention are studied simultaneously: the sequencing batch reactor (SBR) and the sequencing batch biofilm reactor (SBBR). At a temperature of 30 degrees C, the inhibition of nitrite-oxidizing bacteria due to high ammonia concentration has been studied in order to obtain a stable nitrite accumulation. This work has confirmed the effect of pH and dissolved oxygen on nitrite accumulation performance. During a two month starting period, both processes led to nitrite accumulation without nitrate production when pH was maintained above 7.5. From a 500 mgN/L effluent, the performance of the SBR, and the SBBR, reached respectively about 0.95gN-NO2-/gN-NH4+, and 0.4gN-NO2-/gN-NH4+. The SBBR appears to be more stable facing disturbances in dissolved oxygen conditions. Finally, the maximal phosphate removal rates obtained in the SBR reached 90%, and 70% in the SBBR, depending on ammonium accumulation in the reactor. Ammonium phosphate precipitation is likely to occur, as was suggested by crystals observation in the reactor.

High Gradient Magnetic Separation Combined With Electrocoagulation and Electrochemical Oxidation for the Treatment of Landfill Leachate

Landfill leachate was treated in a bench scale plant by high gradient magnetic separation combined with electrocoagulation using iron electrodes and electrochemical oxidation. The electrocoagulation with iron electrodes was used as a magnetic seeding method for phosphorus and organic compounds. Some organic compounds in landfill leachate was coagulated by iron(II) hydrates or hydroxides produced from iron electrodes. Phosphorus in landfill leachate was also suspended as iron phosphate. These magnetized solids were removed by high gradient magnetic separation using a superconducting magnet. The removal rate of total phosphate (T-P) was approximately 90% at a flow rate of 100 L/h. Residuals in the effluent of magnetic filter such as ammonium nitrogen (NH/sub 4/ - N) and chemical oxygen demands (COD) were destroyed by electrochemical oxidation using Ti/PbO/sub 2/ anode. The hypochlorite generated from oxidation of chloride in leachate might play a key oxidant in the effective removal of NH/sub 4/ - N. The experimental result showed that the pretreatment combined process of electrocoagulation using iron electrodes and high gradient magnetic separation might improve the charge efficiency in electrochemical oxidation. Several chemicals that were suspected of having environmental endocrine disrupting effects was also decreased.

Short-term algal toxicity test based on phosphate uptake

In order to develop a short-term algal toxicity test, the growth of and the phosphate uptake by the green alga Selenastrum capricornutum during batch culture were observed. In the control medium, S. capricornutum took up phosphate earlier than it grew. It was also observed that the phosphate uptake was inhibited by the presence of a toxicant. From these results, phosphate uptake was considered as one of the useful effect parameters for a short-term algal toxicity test. As the removal rate of phosphate from the medium is a function of the amount of algal cell initially inoculated, the test period is variable. The relationship between the amount of inoculation and phosphate uptake was examined and the test conditions suitable for a 3-h toxicity test were established as one example. According to this test procedure, the inhibitory effect of some toxicants on the phosphate uptake was determined. For comparison, a conventional algal assay based on algal growth was also performed. The EC50 s for both tests were close. This indicated that the algal toxicity test method proposed in this paper would be useful for the uses where rapidity is required.

High-rate algal pond treatment for water reuse in an integrated marine fish recirculating system: effect on water quality and sea bass growth

A high-rate algae pond (HRAP) was tested as a second loop of water treatment in a recirculating fish rearing system to reduce water requirements and nutrient discharge levels. Three duplicated groups of sea bass (mean initial body weight 35±11 g) were reared under different system conditions (flow-through system, recirculating system and recirculating system with HRAP) for 1 year. Fish survival rate was higher in the system with HRAP, and their mean body weight was statistically higher ( p<0.05) during the month of maximal climatic conditions for algae photosynthesis. After 266 days of experiment, mean fish weight was significantly higher ( p<0.05) in the flow-through system than in the recirculating systems. Final fish weight was 15% higher in the flow-through system than in recirculating systems and was related to a higher daily-ingested food. The comparison of mean annual nutrient concentrations in the recirculating systems gives a statistically significant reduction of 25% of nitrogen ( p<0.01) and 9% of phosphates ( p<0.01) due to the HRAP. Absorption of nitrate form is responsible for nitrogen removal and is related to climatic conditions for algae growth. The phosphate precipitation at high pH (above 8) was not considered. The maximal removal rates were 0.5±0.2 g N m −2 day −1 and 0.03±0.02 g P m −2 day −1 for nitrates and phosphates, respectively, and were obtained during the optimal climatic conditions and the shortest algae harvesting frequency. These results are favourable to complete reuse of the HRAP treated water, all year long, in the recirculating rearing systems. In order to improve nitrate and phosphate removal rates, a periodic harvesting of algae is necessary and a higher water inflow in HRAP should partly make up for inorganic carbon depletion in high nitrate and phosphate effluents.

하천고수부지 수질정화 자유수면인공습지의 초기운영단계 인제거

Phosphorous removal rate and emergent plant growth were examined of a surface-flow constructed treatment wetland system, whose dimensions were 31 meter in length and 12 meter in width. The system was established on floodplain in the down reach of the Kwangju Stream in Korea in one and half months from May to June 2001. Cattails(Typha angustiflora) were transplanted in the system. They were dug out of natural wetlands and stems were cut at about 40 cm height from their bottom ends. Water of the Kwangju Stream were funneled into it via a pipe by gravity flow and its effluent were discharged back into it. The stems of cattails grew from 45.2 cm in July 2001 up to 186 cm in September 2001 and the number of cattail stems per square meter increased from 22 in July 2001 to 53 in September 2001. The early establishment of cattails was good. Volume and water quality of inflow and outflow were analyzed from July 2001 through December 2001. Inflow averaged <TEX>$40\;m^3/day$</TEX> and hydraulic retention time was about 1.5 days. The concentration of total phosphorous in influent and effluent was 0.85 mg/L, 0.41 mg/L, respectively. The average removal rate of total phosphorous in the system was about 52%. The retention efficiency was slightly lower, compared with that in surface-flow wetlands operating in North America, whose retention efficiency was reported to be about 57%. The lower abatement rate could result from the initial stage of the system and inclusion of two cold months into the six-month monitoring period. Root rhizosphere in wetland soils and litter-soil layers on bottoms were not properly developed. Increase of standing density of cattails within a few years will establish both root zones and substrates beneficial to the removal of phosphorous, which may lead to increase of the phosphorous retention rate. The system was submerged one time by heavy storm during the monitoring period. The inundation, however, scarcely disturb its environment.

Phosphate Recovery from Greenhouse Wastewater

A study was conducted to investigate the suitability of phosphate recovery from greenhouse wastewaters by using precipitation/crystallization process. More than 90% of the phosphate could be removed from the greenhouse wastewater. Various calcium phosphate salts were obtained in the process; hydroxyapatite [Ca5(PO4)3OH] could be the main product from the precipitates. Phosphate removal was affected by the presence of magnesium ion in wastewaters. An increase of magnesium concentrations in wastewaters decreased phosphate removal rates. The chemical contents of precipitates in terms of calcium, magnesium and phosphate were affected by calcium to magnesium molar ratio. Higher calcium contents were obtained at wastewaters with high calcium to magnesium molar ratio. An addition of magnesium did not affect the potassium contents in the precipitates. K‐struvite, MgKPO4·6H2O, was not the major product in the precipitate, even with addition of a large quantity of magnesium.

The catalytic effect of Mg 2+ and imidazole on the decomposition of 5-phosphoribosyl-α-1-pyrophosphate in aqueous solution

The rate of decomposition of aqueous solutions of 5-phosphoribosyl-α-1-pyrophosphate (PRPP) is greatly enhanced by the presence of certain divalent ions. High levels of Mg 2+ were shown to increase the rate of phosphate removal from PRPP by factors greater than 100-fold. The combined action of Mg 2+ and a nitrogenous compound (imidazole was employed in this study) increases the degradation rate constants by up to 1000-fold. The degradation of PRPP in neutral solutions follows two main paths, a pyrophosphate hydrolysis reaction yielding ribose 5-phosphate and an internal β-phosphate cleavage yielding 5-phosphoribosyl-1,2 cyclic phosphate. The catalytic effect of Mg 2+ on PRPP degradation appears to suggest a connection between the observed rate enhancements and the dimagnesium form of PRPP. Rate enhancing effects of Mg 2+ are greatest at pH values (i.e. pH>7) which promote strong phosphate–Mg 2+ interaction.

Prediction of adsorption rate of phosphate removal from wastewater with gas concrete

Gas concrete, a conventional structural material, is used to remove phosphate from wastewater. A batch study of phosphate removal from wastewater with waste particles of gas concrete has been performed. The concentration-time graphs were plotted against pH, temperature, and agitation speed, and the reaction rate equation was adapted to adsorption. The differential method was used to define reaction rate. The adsorption rates, reaction rate constants, and reaction rates were determined by tangent lines of drawn curves at different concentrations, depending on pH, temperature, and agitation speed. The adsorption rate increased with pH and temperature. The maximum effect of agitation speed on the adsorption rate was observed at 150 rpm. The activation energy of reaction and the pre-exponential factor were calculated using the Arrhenius equilibrium equation. The zeta potentials of waste gas concrete were determined at various pH values. The surface area of gas concrete was obtained using BET apparatus as 22 m²/g. The composition of gas concrete was determined by X-ray diffractometry. The results indicate that gas concrete is an effective adsorbent to remove phosphate from wastewater.

Phosphate removal and recovery by a novel electrolytic process

The possibility of removing and recovering phosphate from wastewater by a novel electrolytic process was investigated experimentally. In the process, ion electrodes are immersed in synthetic wastewater and direct current (DC) is applied to coagulate phosphate on the surface of the anode. Experimental results demonstrated that at electric current densities ranged from 0.001 to 0.1 mA/cm2, phosphate was removed and recovered as phosphate-rich aggregates formed on the anode surface. Decreases in phosphate concentration at bulk liquid were in fairly good agreement with the amounts of phosphate in the aggregates. Moreover, the removal rate of phosphate was increased with increasing electric current. In addition, as heavy metal anions such as Cu2+ deposit on the counter electrode (cathode), it was thought that relatively pure phosphate could be obtained by the present process.

ENHANCED NUTRIENT REMOVALS USING CONVENTIONAL ANOXIC BIOMECHANIC AEROBIC SYSTEM FOR ON-SITE WASTEWATER TREATMENT

ABSTRACT A bench-scale absorbent biofilter system combined with a conventional anoxic process was investigated in regard to its feasibility for removing organic as well as nutrient materials from small community wastewater in Korea. A polyurethane biofilter medium with high porosity and a large surface area were used for the aerobic system. Part of treated wastewater was recirculated into the anoxic process to promote removal rate of nutrients. At three different ratios of recirculation, the BOD and SS of treated wastewater satisfied standard regulations for a small wastewater treatment facility (10 mg/l) during the overall experimental period. The system reduced the concentration of BOD from approximately 130 mg/l to 6.1 (removal rate of 95.2%) and 1.7 mg/l (removal rate of 98.7%). These results correspond to recirculation ratios of 1 and 2, respectively. A further increase of the recirculation ratio did not significantly improve the removal rate or further reduce effluent BOD concentration. Nutrients such as nitrogen and phosphorus also were removed effectively, with maximum removal rates of 65.3 and 84.1% for nitrogen and phosphorus, respectively. The recirculation ratio for optimum nitrogen removal was 2, while the removal of phosphorus continued to increase across the entire range of recirculation ratios tested. With a recirculation ratio of 2, the total phosphorous removal rate increased dramatically as initial ammonium concentration increased, while nitrogen removal was not affected in this manner. During the experimental period of 2 years, the system was quite stable, requiring the minimum amount of maintenance and a relatively low cost compared to other utility expenses. Based on the experimental data, the proposed anoxic-biofilter aerobic recirculation system might be used as a new alternative technology for wastewater treatment in small communities in Korea.

3-Methyladenine-DNA Glycosylase (MPG Protein) Interacts with Human RAD23 Proteins

Human 3-methyladenine-DNA glycosylase (MPG protein) initiates base excision repair by severing the glycosylic bond of numerous damaged bases. In comparison, homologues of the Rad23 proteins (hHR23) and the hXPC protein are involved in the recognition of damaged bases in global genome repair, a subset of nucleotide excision repair. In this report, we show that the hHR23A and -B also interact with the MPG protein and can serve as accessory proteins for DNA damage recognition in base excision repair. Furthermore, the MPG.hHR23 protein complex elevates the rate of MPG protein-catalyzed excision from hypoxanthine-containing substrates. This increased excision rate is correlated with a greater binding affinity of the MPG protein-hHR23 protein complex for damaged DNA. These data suggest that the hHR23 proteins function as universal DNA damage recognition accessory proteins in both of these major excision repair pathways.

Treatment performance of a multistage constructed wetland at 69° north, Norway

Fagernes, the only constructed wetland for wastewater treatment in the north of Norway, is located in the municipality of Lenvik. Despite the challenges presented by a cold climate the wetland has been operating well, and chemical and microbiological analyses shows that treatment efficiencies are high. This is particularly the case for COD and phosphorus. Total treatment efficiency for Tot‐N was very high (78%) in comparison with Haugstein, a similar wetland system in southern Norway. In Fagernes, a vertical flow pre‐treatment filter with light‐weight aggregates (Filtralite) aerates the wastewater, stimulates nitrification and binds phosphorus. Both horizontal subsurface flow wetlands (with sand and with light‐weight aggregates) have high phosphorous removal rates.

Biodegradation of low aqueous concentration pentachlorophenol (PCP) contaminated groundwater

Bioremedial treatment to remove low level organic contamination to regulatory standards has met with limited success. In this study source water from a contaminated surficial aquifer at a former wood treatment facility was used to evaluate the potential for indigenous microorganisms to degrade low level (<1.0 mg) pentachlorophenol (PCP) to a regulatory drinking water standard of 0.001 mg/L. PCP degradation was evaluated in series of batch reactors in a two phase study to (a) determine the rate and extent of PCP removal and (b) evaluate the impact of nutrient amendment (N and P) on removal rate. All reactors with the exception of the abiotic control demonstrated PCP removal to a level < 0.002 mg/L within a maximum period of 32 d with and without nutrient amendment. A regression analysis of reactive phosphate (ortho-P) concentration versus removal rate produced an R 2 of 0.94 (p= 0.006) indicating a significant correlation between the level of available phosphate and PCP degradation rate. Selective bacterial enumeration (for PCP degrading bacteria) revealed PCP-degrading bacteria increased in abundance prior to and in conjunction with the degradation phase to a density of between 10 3 to 10 4 CFU/ml. Isolates were also analyzed for total fatty acids using Fatty Acid Methyl Ester (FAME) methodology and the results indicated that PCP degrading bacteria were present in the aquifer and consisted of predominately fluorescent, oxidase positive Pseudomonas species. Overall, data indicate that autochthonous microbes are capable of removing low level PCP (<1.0 mg/L) to approach if not reach the regulatory standard of 0.001 mg/L with the addition of oxygen, with or without nutrient amendment. Results of this research can be applied to full-scale implementation of in-situ or ex-situ bioremediation of groundwater at former wood treatment facilities.

Simultaneous Nitrogen and Phosphate Removal by the Intermittent Cyclic Process

By using the Intermittent Cyclic (IC) process which repeats aerobic and anaerobic conditions in an 18-m3 pilot plant reactor, domestic sewage was treated at a rate of 18 m3 per day. Operating condition was 4 cycles per day, intermittent aeration--4 hours, settling--1 hour, drawing--1 hour. Seven months of operation recorded high nitrogen removal rates: mean 86% and maximum 96%, phosphate removal rates: mean 83% and maximum 93%. Compared with conventional aerobic/anaerobic processes, the IC process, one of batch-type treatment processes, can advantageously and stably remove nitrogen and phosphate with repeated aeration and nonaeration under optimal control.

Calcium Phosphate Precipitation: Identification of Kinetic Parameters in Aqueous Limestone Suspensions

AbstractPhosphate disappearance from aqueous calcitic limestone suspensions was described using an equation for interface‐, controlled crystal growth following addition of hydroxyapatite seed crystals. Phosphate removal from solution exhibited second order dependence on the phosphate concentration. Hydroxyapatite seed crystals were more important than limestone in governing phosphate removal. Limestone functioned primarily to buffer the activities of (Ca2+) and (OH‐). At pH 8.5, an increase of 0.1‐millimolar (mM) NaF caused a fivefold increase in the rate constant. Twenty successive reactions of limestone with phosphate caused a fourfold increase in the phosphate removal rate. A portion of freshly precipitated calcium phosphate probably served as seed for development of new crystals. Participation of both (F‐) and hydroxyapatite crystals suggests a mixture of fluorapatite and hydroxyapatite, or an apatite precursor formed in the experiments.