Phosphates removal from wastewater

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. 

H. L, Recht and M. Ghassemi, "Kinetics and Mechanism of Precipitation and Nature of the Precipitate Obtained in Phosphate Removal from Wastewater Using Aluminum(III) and Iron(III) Salts," Report No. 17010EKI 04/70, U.S. Dept, of Interior, Federal Water Quality Adm., Cincinnati, 1970. 

The importance of redox effects on coupled iron-phosphorus cycling in freshwater systems has been the subject of study in applied environmental science, where phosphate removal from eutrophic natural waters and wastewaters, by sorption onto Fe-oxyhydroxide phases, has been explored as a remediation measure. Phosphate also has a pronounced tendency to sorb onto Al-oxyhydroxides, and these phases have been used in remediation of phosphate overenriched aquatic systems, as well (e.g., Leckie and Stumm, 1970). 

Cr removal from wastewater 31-P-13 Crystallisation, MFl, phosphate-affected 02-P-40 ... 

Using Eq. 6-37, we can determine Ct.po (= Ct,ai) cts a function of pH. This relationship is plotted in Fig. 6-13. It shows that AlP04(s) has a minimum solubility in the neighborhood of pH 5.5. This information is useful to us because it indicates that it would be inappropriate to attempt AlP04(s> precipitation for phosphate removal from solutions containing in the range of 10 to 10 mole P04/liter (which is typical of wastewaters) at... 

A review of the early sorption rate literature for phosphate is given in J. C. Ryden and P. F. Pratt, Phosphorus removal from wastewater applied to land, Hilgardia 48 1 (1980). See also J. A. Veith and G. Sposito. ... 

Precipitation is often applied to the removal of most metals from wastewater including zinc, cadmium, chromium, copper, fluoride, lead, manganese, and mercury. Also, certain anionic species can be removed by precipitation, such as phosphate, sulfate, and fluoride. Note that in some cases, organic compounds may form organometallic complexes with metals, which could inhibit precipitation. Cyanide and other ions in the wastewater may also complex with metals, making treatment by precipitation less efficient. A cutaway view of a rapid sand filter that is most often used in a municipal treatment plant is illustrated in Figure 4. The design features of this filter have been relied upon for more than 60 years in municipal applications. 

Chimenos, J.M. et al.. Removal of ammonium and phosphates from wastewater resulting from process of cochineal extraction using MgO-containing by-product. Water Res., 37, 1601, 2003. 

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. 

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. 

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

H. Ohtake, A. Kuroda, J. Kato and T. Ikeda (1999). Genetic improvement of bacteria for enhanced removal of phosphate from wastewater. In H. C. Schroder and W. E. G. Muller (Eds.), Inorganic... 

Several examples of the applications of SLMs in the removal of antibiotics from wastewater are shown below. Kawasaki et al. [154] studied the application of the flat-sheet SLM in the removal of erythromycin A from aqueous matrices. The feed phase consisted of citric acid (concentration = 0.025 mol dm 3), boric acid (concentration = 0.100 mol dnr- j, and sodium phosphate (concentration = 0.050 mol dm ). The SLM was prepared from PTFE flat sheet porous with 1-decanol as the diluent. 

Many bodies of water become eutrophic when excess phosphate from detergents and fertilizer washes in. This overenrichment results in undesirable algal blooms. Agents that complex phosphate may allow it to be removed from treated wastewater, recovered, and reused. The first com plexing agent (7.22) (where X = S) complexes dihydrogen phosphate with a K of 820 and acetate with a K of 470 chloride, hydrogen sulfate, nitrate, and perchlorate are held much more weakly.91 The Kfor the second one with phosphate (7.23 where R is H) is 12,000.92... 

Results of A1P04( s) precipitation from wastewater agree in general with the above observations. An optimum pH of about 6 was observed and it was necessary to use twice as much aluminum salt as required for phosphate precipitation because Al(OH)3ts> also precipitated. Also, the A1(OH)3(si was of importance because it aided the removal of the fine, rather difficult to settle, AlP04 s). 

Florentz, M. and Granger, P. (1983) Phosphorus-31 nuclear magnetic resonance of activated sludge use for the study of the biological removal of phosphates from wastewater. Environmental Technology Letters 4, 9-14. 

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