[ effect of solid waste compost on leaching and adsorption of heavy metals from silt-loamy soils]

Leaching of nutrients and heavy metals from municipal solid waste compost leads to accumulation of certain elements in soil layers, causing underground water pollution. The objective of this study was to investigate the effect of compost on leaching and adsorption of heavy metals and nutrients [sodium, potassium, and sulfate] from silt-loamy soils. In this empirical, applied study, three polyethylene columns [height 50 cm, inner diameter 10 cm], filled with sandy clay loam soil, were randomly selected. Then, 10 kg of compost per square meter were sprayed onto the columns, and leachates exiting the columns were routinely analyzed for pH, electrical conductivity, sulfate, sodium, potassium, lead, chromium, and cadmium. Data analysis was performed with Excel and SPSS software using Kruskall-Wallis test. The data showed that the use of enriched and unenriched compost leachate decreased pH [from 7.43 +/- 17.0 to 6.7 +/- 0.25 and 7.07 +/- 0.11, respectively] and increased the electrical conductivity [EC] [from 1.8 +/- 0.3 mSiemens/m to 3.7 +/- 0.12 and 12.87 +/- 0.41 mSiemens/m respectively]. Leakage of metals in the unenriched treatments was not significantly different from the control [p > 0.78], but leakage with three metal-enriched compost applications was significant compared with control [p < 0.001]. Application of composts containing heavy metals onto loamy soils increases leaching of heavy metals from the compost into groundwater. Therefore, frequent use of compost endangers groundwater quality

Fluoride removal from water by adsorption using Bagasse, Modified Bagasse and Chitosan

Fluoride is widely used in industries such as manufacture of semiconductors, power plants, glass production etc and release to the environment via their effluents. The purpose of this sturdy was to compare the efficiency of low price adsorbents in fluoride removal from water. The optimum values of pH, contact time and adsorbent dosage were determined and different concentrations of fluoride were experimented in lab scale conditions for bagasse, modified bagasse and chitosan. Then Langmuir and Freundlich coefficient were determined based on optimum conditions. The pH value of 7. contact time of 60 min and adsorbent dosage of 2 g/L were determined as optimum conditions for all three adsorbents. The most fluoride removal efficiency of 91% was obtained for modified bagasse in optimum conditions. Based on data obtained in this study, it can be concluded that adsorption by modified bagasse is an efficient and reliable method for fluoride removal from liquid solutions

[Survey of ability of activated sludge isolated bacteria in removal of RB-B dyestuff from aqueous medium]

Reactive dyestuff has potential of toxicity, carcinogenesis and mutagenesis for mammals and aquatic organisms. The current physical and chemical methods such as adsorption, coagulation, precipitation, filtration and. can been used for removing of dyestuff. Biological treatment which is effective and economic for decontamination of dyestuff wastewaters was preferred because of limitation and difficulty of physicochemical methods. In order to investigate the trend of pollution reduction of color compounds, ability of Remazol Black-B dyestuff removal from aqueous medium by bacterial consortium under anoxic conditions was studied. The mix culture of bacteria from textile industries activated sludge was enriched in luria broth medium containing RB-B dyestuff as a carbon source. Then biodegradation was assessed in 4 batch reactors. Microbial population of bacterial and decolorization quantities of samples were detected by MPN and UV-Vis spectrophotometer. Decolorization efficiency by the bacterial consortium was obtained more than 99% for 50 and 250 mg/L concentrations in 72 and 144 h [3 and 6 days] respectively, while for the initial concentration of 500 mg/L was 98.1in 240 h [10 days] of biodegradation period. Dyestuff reduction rate after completed removal was about 0.69, 1.74,2 mg/L/h for initial concentration of 50, 250, 500 mg/L respectively. Results showed that Alcaligenes denitrificans and Alcaligenes xylosoxidans bacteria which were isolated from activated sludge have good potential of RB-B dyestuff removal and this removal is depending on primary concentration of dye. Removal efficiency increased as primary concentration went up

Influence of bioaugmentation in biodegradation of PAHs-contaminated soil in bio-slurry phase reactor

Polycyclic Aromatic Hydrocarbons [PAHS] are important pollutants which have toxic, carcinogenic and mutagenic properties and are considered as a serious hazard to human health and environment. Bioremediation of PAHs contaminated soil was studied in the soil slurry phase bioreactor. For enhancement of biodegradation, bioaugmentation [which is the process of adding microorganisms with the potential of pollution biodegradation to the bio-slurry reactor] was applied. Phenanthrene [C[14]H[10]], a three-benzene ring PAHs, was added in concentration of 100mg/kg soil. Two isolated species and consortium of bacteria were inoculated to the medium in density of 7_10[7] CFU/mL. The analysis of variance [ANOVA] was used for finding of optimum levels of type of bacterial culture and presence effect of endogenous factors. The base of the bacteria was petroleum-contaminated soil from around Tehran petroleum Refinery. Control reactor [killed bacteria] showed 5% loss of phenanthrene and biodegradation in the non-augmented reactor [endogenous microorganisms] in a slurry bioreactor was about 17%. In the case of bioaugmentation with Pseudomonas.spp, Pseudomonas aeruginosa and consortium, phenanthrene degradation efficiency were 87.8%, 85.5% and 92.8%, respectively, presenting the positive effect of biodegradation in consortium augmented compared to the isolated one. Colony forming units [CFUs] variation showed good conformity and agreement with the performance of the reactors with respect to phenanthrene degradation. Hence, the results of this experiment show that bioaugmentation may be considered as an effective method to enhance the bioremediation in removal of PAHs from contaminated soils

[Leachate treatment by batch decant activated sludge process and powdered activated carbon addition]

Direct biodegradation of landfill leachate is too difficult because of high concentrations of COD and NH3 and also the presence of toxic compounds. The main objective of this study was to application of Strurvite precipitation as a pretreatment stage, in order to remove inhibitors of biodegradation before the batch decant activated sludge process with addition of powdered activated carbon [PAC]. Strurvite precipitated leachate was introduced to a bench scale batch decant activated sludge reactor with hydraulic retention times of 6 and 12 hour. PAC was added to aeration tank directly at the rate of 3.5 g/L. TCOD, SCOD, NH3 and P removal efficiency with addition of PAC in HRT of 6 h were 90, 87, 98.3 and 94% respectively and 96, 95, 99.2 and 98.7 5 in HRT of 12 h. According to obtained data from this work, it can be concluded that Strurvite precipitation before batch decant activated sludge process and simultaneous addition of PAC is promising technology for leachate treatment and can meet effluent standards for discharge to the receiving waters

[Survey of phenantherene biodegradation's model in contaminated soils by Acinetobacter sp]

Polycyclic aromatic hydrocarbons [PAHs] are a group of hazardous pollutants which have carcinogenic and mutagenic properties and accumulated in environment by different actions, therefore treatment of them is important. Biological treatments are simple and cheep technologies. This technology was recommended as a cost- effective method for treatment of these pollutants. In order to investigate the trend of pollution reduction of petroleum hydrocarbons in bioremediation, the phenanthrene biodegradation's model in contaminated soils was studied. Firstly, PAHs capable degrading bacteria was isolated from petroleum contaminated soils and then their ability for biodegradation of phenanthrene was assessed in slurry phase. After that by using Acinetobacter which have the most potential of removing phenanthrene from soil, the biodegradation model was investigated in bench scale. Phenantherene removal efficiency was obtained 99.4% for 100 mg/kg and 96% for 500 mg/kg concentrations in 33 and 60 days biodegradation period respectively. Phenantherene reduction rate varied from 2.99 to 8.86 and 1.4 to 11.09 mg/kg/day for 100 and 500 mg/kg concentrations, respectively. Rate of phenantherene removal is depended on primary concentration of contamination and by increasing of primary concentration, phenantherene removal rate was increased. Also removal efficiency followed zero and first order kinetic model with good correlation

[Optimization of propylene removal in a complete mixed activated sludge bioreactor by Taguchi method]

Exposure to propylene glycol can lead to many health risks on blood, skin and kidney. Biodegradation of synthetic wastewater containing propylene glycol was studied in a continuous conventional activated sludge bench scale reactor. Optimum conditions of microorganisms growth for biodegradation of propylene glycol were determined by Taguchi method. Primary microorganisms for start up of the bioreactor were obtained from sludge return line of a municipal wastewater treatment plant and adapted to different concentrations of propylene glycol in a conventional activated sludge reactor. Optimum growth conditions of microorganisms and also operational conditions of the system including pH, influent COD, source of nitrogen and salinity were determined in three levels by Taguchi method. COD removal efficiency in conventional activated sludge reactor for influent concentrations of 400, 700, 900, 1100 and 1300 mg/L were 98%, 95%, 95%, 90% and 85% respectively. Optimization of the process by Taguchi method showed that source of nitrogen urea, pH = 8, salinity of 8% and influent COD of 1300 mg/L with importance priority of 41%, 25%, 17.11% and 16.142% were as optimum growth conditions of microorganisms and also, operational conditions of the system for propylene glycol biodegradation respectively. According to the results obtained from this work, it can be concluded that optimum conditions of biological processes and improvement the efficiency of bioreactors can simply be done by the use of such experimental designs