Phosphate removal

Points of Chemical Addition In independent physical-chemical treatment or in phosphate removal in the primary clarifier ahead of biological treatment, chemicals are added to raw sewage. In tertiary treatment for phosphate removal and suspended solids (SS) reduction, they are added to secondary effluent. In both cases, proper mixing and flocculation units are needed. For phosphate removal or improvement of SS capmre in biological secondary treatment, chemicals are often added directly to aeration units or prior to secondary settling units, without separate mixing and flocculation. In some phosphate removal applications coagulants are added at... 

Single-strand conformation polymorphism (SSCP) Wastewater bioreactors (including denitrifying and phosphate-removal system, Chinese traditional medicine wastewater treatment system, beer wastewater treatment system, fermentative biohydrogen producing system, and sulfate-reduction system) Microbial community structures, diversity and distribution in different wastewater treatment processes, and relationship between the structures and the status of processes [157]... 

Phosphate removal by sorption on Fe(lIIX)OH is particularly important in the vicinity of mid-ocean ridges and rises because hydrothermal activity supports a large flux of... 

McGrath, J.W. Quinn, J.P. Phosphate Removal a Novel Approach, School of Biology and Biochemistry, Queens University Belfast, Ireland, 2002 http //www.qub.ac/uk/envres/EarthAir-water /phosphate-removal.htm. 

Fluidized-Bed Process for Phosphate Removal by Calcium Phosphate Crystallization... 

We have proposed a fluidized bed type process, which can be applied to phosphate removal from wastewater containing phosphate 2-23 mg/jg as P.By the results of experiments using equipment of capacity l-4m3 /day, factors such as supersaturation, recirculation ratio and space velocity were recognized to affect crystallization rate or phosphate removal efficiency. By mathematical analysis, we could obtain the characteristic equation for fluidized bed process, to agree well with experimental results. 

Phosphate removal processes from wastewater have been studied by many workers, in order to protect stagnant water area, such as lakes and coastal region from eutrophication. Among conventional phosphate removal processes, the representative one was flocculation and sedimentation process, which was based on precipitation of insoluble metal phosphate or hydroxide. However, the main problem with this process, is to produce large amounts of sludge, which is difficult to dehydrate. 

To cope with these problems, we have developed phosphate removal process using crystallization, which can minimize the amount of sludge and recover phosphate. Mechanism of this process is crystallization of calcium phosphate on the surface of phosphate rocks by contacting supersaturated solution with them. In case of application to wastewater containing 1-3 mg/jg phosphate as P, we proposed fixed bed type process, which has demonstrated excellent performance in the sewage treatment. 

Table 1 shows the performance of fixed bed type process, in application to various wastewaters. The merit of this process is stability in ability of phosphate removal and low sludge production. Sludge production of this process is from 1/5 to 1/10 lower than that of the conventional flocculation and sedimentation process. 

We have now proposed fluidized bed type process, which can be applied to wastewater, containing from 2 to 23 mg/jg phosphate as P. This report reveals fundamental studies on factors affecting phosphate removal and crystallization rate in the fluidized bed process. 

Figure 1 shows the schematic illustration of phosphate removal mechanism. Phosphate in wastewater contacts with seeds made of phosphate rock, after chemical conditioning such as supply of calcium and hydroxide ion. Then calcium phosphate, mainly hydroxyapatite, crystallizes, according to eq.(l), on the surface of phosphate rocks. 

In this experiment, tap water with added phosphate was used as influent. Concentration of phosphate was adjusted to an adequate range from 2 to 23 mg/jg. Calcium chloride and sodium hydroxide solution were added to maintain calcium concentration from 70 to 100 mg/jg and pH of the effluent from 9.0 to 9.5. Using this equipment, we performed experiments to obtain efficiency of phosphate removal, relationship between phosphate concentration, and crystallization rate and factors affecting phoshate removal. 

Figure 8 shows effect of recirculation ratio and space velocity. Horizontal line shows total PO4 as P in the influent and vertical line does total phosphate in the effluent. Black circles were data obtained from the experiments in case that recirculation ratio was 0 and space velocity 38 1/h. White circles were obtained, in case that recirculation was 2 and space velocity 13 1/h. Solid line and dotdash line shows theoretical values calculated from eq.(8), to agree well with experimental results. Increasing in recirculation ratio and decreasing in space velocity was recognized to improve phosphate removal efficiency. 

We have proposed fluidized bed process and by the results of experiments, factors such as supersaturation, recirculation ratio and space velocity affected crystallization rate or phosphate removal efficiency, and experimental results agreed well with calculated values from characteristic equation. 

We have reported only the results of the last investigation of fundamental properties of this process. But there are many problems remaining unsolved such as growing mechanism of calcium phosphate, the reason of difference in phosphate removal efficiency between application to wastewater and tap water, and also how contaminants include into growing calcium phosphate. 

Our results show that coprecipitation of the REE with phosphate removed Ce, Pr, Nd, Sm, and Eu more easily from the brine than other REE. This finding might be of importance for the mobility of trivalent Am and Cm in a radioactive waste salt repository, because for these elements, owing to their almost identical ionic radii, an almost analogous geochemical behaviour is expected as for Sm and Nd (Choppin 1983 Krauskopf 1986). These radionuclides would, in the case of a leaking HLW salt repository, probably be retained when phosphate minerals are present in the backfill material. 

Sucrose synthesis in the cytosol and starch synthesis in the chloroplast are the major pathways by which the excess triose phosphate from photosynthesis is harvested. Sucrose synthesis (described below) releases four Pi molecules from the four triose phosphates required to make sucrose. For every molecule of triose phosphate removed from the chloroplast, one Pj is transported into the chloroplast, providing the ninth Pj mentioned above, to be used in regenerating ATP. If this exchange were blocked, triose phosphate synthesis would quickly deplete the available Pj in the chloroplast, slowing ATP synthesis and suppressing assimilation of C02 into starch. 

Gieseke, A., U. Purkhold, M. Wagner, R. Amann, and A. Schramm. 2001. Community structure and activity dynamics of nitrifying bacteria in a phosphate-removing biofilm. Applied and Environmental Microbiology 67 1351-1362. 

Untreated PEUU controls (which had been exposed to GOx) exhibited no stain after continuous stirring in SDS, Triton, and sodium phosphate. GOx-PPNVP/PEUU samples washed by the same method as well as PEUU controls washed by less stringent methods exhibited positive stain. Thus the immunochemical stain assay demonstrated that the continuous wash in SDS, Triton, and sodium phosphate removed physically adsorbed GOx from the surface of GOx-PPNVP/PEUU, leaving covalently bound GOx. Positive stain was easily observable with the naked eye, making the immunochemical stain an effective novel technique for the quick screening of wash procedures for thin film samples. 

R. P. X. Hesselmann, C. Werlen, D. Hahn, J. R. van der Meer and A. J. B. Zehnder (1999). Enrichment, phylogenetic analysis and detection of a bacterium that performs enhanced biological phosphate removal in activated sludge. System. Appl. Microbiol., 22, 454-465. 

A. Hiraishi, Y. Ueda and J. Ishihara (1998). Quinone profiling of bacterial communities in natural and synthetic sewage-activated sludge for enhanced phosphate removal. Appl. Environ. Microbiol., 64, 992-998. 

J. W. McGrath and J. P. Quinn (2003). Microbial phosphate removal and polyphosphate production from wastewaters. Adv. Appl. Microbiol., 52, 75-100. 

H. Melasniemi and A. Hernesmaa (2000). Yeast spores seem to be involved in biological phosphate removal a microscopic in situ case study. Microbiology, 146, 701-707. 

T. Mino (2000). Microbial selection of polyphosphate-accumulating bacteria in activated sludge wastewater treatment process for enhanced biological phosphate removal, Biochemistry (Moscow), 65, 541-549. 

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