Recovery of phosphate as hydroxyapatite by fluidized bed homogeneous crystallization technique.

Phosphorous recovery from aqueous solutions gained substantial attention and this not only secure the food demand but also curtail the pollution of freshwater courses. In the current study, authors employed novel fluidized bed homogeneous crystallization (FBHC) technique to granulate the phosphorous as hydroxyapatite (HAP). FBHC technique nurtures the formation of high pure HAP crystals without seed addition and potential technique to recover phosphorous compared to other techniques. The key operational parameters influencing the HAP crystallization were analyzed prior to FBHC by batch analysis. From the batch study results, the range of pH and calcium to phosphorous molar ratio fixed for FBHC studies. Maximum phosphate removal and granulation efficiencies obtained were 91.25% and 82.55%, respectively, at 500 mg/L phosphate concentration, pH 12, and calcium to phosphorous molar ratio 1.65. Box-Behnken design of response surface methodology was employed for evaluating interaction impact of process parameters on granulation efficiency. Granulation efficiency of 79.74% was attained at pH 11.83, calcium to phosphorous molar ratio 1.637, and reaction time 70.73 h.

Bioclogging in porous media: influence in reduction of hydraulic conductivity and organic contaminants during synthetic leachate permeation.

In this study the concept of biofilm accumulation in the sand column was promoted to assess the changes in hydraulic conductivity and concentration of organic contaminants of the synthetic leachate. Four different combinations of column study were carried out using synthetic leachate as a substrate solution. Mixed and stratified mode of experiments with two different sizes (0.3 mm and 0.6 mm) of sand grains were used for column filling. Two columns were acting as a blank, the remaining two columns amended with mixed microbial cultures which were isolated from leachate. The column was operated with continuous synthetic leachate supply for 45 days. The results indicated that the highest hydraulic conductivity reduction occurred in the mixed sand microbial column with 98.8% when compared to stratified sand microbial column. The analysis of organic contaminants of the effluent leachate was also clearly shown that the mixed sand amended with microbes poses a suitable remedial measure when compared to natural and synthetic liners for controlling the leachate migration in the subsurface environment.

Electrolytic removal of Rhodamine B from aqueous solution by peroxicoagulation process.

Peroxicoagulation treatment of aqueous solution containing hazardous dye, Rhodamine B, with commercially available graphite as cathode and iron as anode has been studied. The effect of various operational parameters such as solution pH, applied voltage, electrode area, other ions, etc. on the dye removal was investigated. The experimental result showed that pH-regulated peroxicoagulation system is an efficient process for the dye removal. Ninety-five percent of the dye was removed after 180 min of electrolysis. Anions such as carbonate, bicarbonate, chloride and sulphate negatively affected the efficiency of peroxicoagulation system. From the present study, it can be concluded that peroxicoagulation process is an efficient tool for dye removal from aqueous solution.

Use of combined coagulation-adsorption process as pretreatment of landfill leachate.

Landfill leachate is an important pollution factor resulting from municipal landfill sites. Physical and chemical processes are the better option for pretreatment or full treatment of landfill leachate. This article presents a combination of pre-treatment method (coagulation and adsorption) for leachate collected from municipal solid waste open dumping site. Physico chemical characteristics of stabilized and fresh leachate were examined. Coagulation process was examined by using alum and ferric chloride. A low cost adsorbent, fly ash was used for adsorption studies. Coagulation studies were carried out for fresh and stabilized leachate. Adsorption studies have been conducted for alum pre-treated stabilized leachate. Effect of coagulant dose, adsorbent dose, pH and contact time were carried out. The effective optimum coagulant dosages were 0.6 g/L and 0.7 g/L for alum and ferric chloride respectively for stabilized leachate and incase of fresh leachate 0.8 g/L and 0.6 g/L for alum and ferric chloride respectively. For the alum pretreated stabilized leachate, the maximum COD removal is 28% using fly ash adsorbent with equilibrium time of 210 min and optimum dose of 6 g/L. Overall COD removal efficiency of 82% was obtained by coagulation using alum and adsorption using fly ash for stabilized leachate. The results obtained showed that combined coagulation and adsorption process can be used effectively for stabilized leachate treatment.

Degradation of dyes from aqueous solution by Fenton processes: a review.

Several industries are using dyes as coloring agents. The effluents from these industries are increasingly becoming an environmental problem. The removal of dyes from aqueous solution has a great potential in the field of environmental engineering. This paper reviews the classification, characteristics, and problems of dyes in detail. Advantages and disadvantages of different methods used for dye removal are also analyzed. Among these methods, Fenton process-based advanced oxidation processes are an emerging prospect in the field of dye removal. Fenton processes have been classified and represented as "Fenton circle". This paper analyzes the recent studies on Fenton processes. The studies include analyzing different configurations of reactors used for dye removal, its efficiency, and the effects of various operating parameters such as pH, catalyst concentration, H2O2 concentration, initial dye concentration, and temperature of Fenton processes. From the present study, it can be conclude that Fenton processes are very effective and environmentally friendly methods for dye removal.