Search

This study aimed to investigate the effect of sodium ferrate synthesized from industrial effluents (SF-W) and that of synthetized from analytical grade chemicals (SF-O) on total organic carbon (TOC) removal from surface water. Response surface methodology (RSM) was used to optimize the operating variables such as pH, dosing rate, rapid mixing time, and gentle mixing speed on TOC removal. A TOC removal of 89.805% and 79.79% was observed for SF-O and SF-W, respectively. Ferrate as SF-O and SF-W demonstrated 26.67% and 8.51% more TOC removal at a lower dosage compared to conventional chemicals such as chlorine, ozone, poly aluminum chloride (PAC) and polyelectrolyte. The optimum conditions of the independent variables including sodium ferrate (SF-O and SF-W), pH, rapid mixing time and gentle mixing speed were found to be 1.54 mg/L and 2.68 mg/L, 8.5, 30 s at 120 rpm for coagulation followed by 20 min of gentle mixing. Economic analysis showed that the application of SF instead of conventional chemicals provides a significant reduction in operational costs by about 68%, mainly because of the reduction of chemicals and energy consumption. [ABSTRACT FROM AUTHOR]

The present study focuses on process imbalances in Danish centralized biogas plants treating manure in combination with industrial waste. Collection of process data from various full-scale plants along with a number of interviews showed that imbalances occur frequently. High concentrations of ammonia or long chain fatty acids is in most cases expected to be the cause of microbial inhibitions/imbalances while foaming in the prestorage tanks and digesters is the most important practical process problem at the plants. A correlation between increased residual biogas production (suboptimal process conditions) and high fractions of industrial waste in the feedstock was also observed. The process imbalances and suboptimal conditions are mainly allowed to occur due to 1) inadequate knowledge about the waste composition, 2) inadequate knowledge about the waste degradation characteristics, 3) inadequate process surveillance, especially with regard to volatile fatty acids, and 4) insufficient pre-storage capacity causing inexpedient mixing and hindering exact dosing of the different waste products. [ABSTRACT FROM AUTHOR]

The lack of potable water in arid countries leads to the use of treated sewage water (TSW) for crop growth. Mercury accumulation (up to 500 ng/g) in agricultural soil originating from daily irrigation with TSW was found at two sites fed separately from a hospital sewage plant and an industrial plant. A control site irrigated with potable water (∣Hg∣ <0.01 ng/ml) had much reduced levels in soil (<12 ng/g). Cold-vapour analysis of TSW revealed that Hg concentrations fluctuated widely, and were between 10-100 times higher than those of potable water. The TSW data originated from a total of 46 samples (1L each), from both plants, collected over a 6-month period. The Hg levels varied from 0.1 to 1.0 ng/ml, which suggested that the possible source of the accumulation could be found in continuous irrigation with comparatively higher Hg levels. Remedial measures could be approached from the perspective of curbing this inconsistency to produce more consistent Hg concentrations below 0.5 ng/ml. It was found that the electrical conductivity of TSW is a useful indicator to rapidly monitor fluctuations in treatment. A novel development in the study was the potential capacity of the plastic TSW discharge-pipes to behave as crude 'chromatographic' columns for possible Hg adsorption. If this property of the pipes is developed further it could have a considerable mitigating effect on the Hg levels. Possible recommendations for remediation to limit the Hg levels and promote sustainable development are discussed. [ABSTRACT FROM AUTHOR]

The diversity and community structure of the β-proteobacterial ammonia oxidising bacteria (AOB) in a range of different lab-scale industrial wastewater treatment reactors were compared. Three of the reactors treat waste from mixed domestic and industrial sources whereas the other reactor treats waste solely of industrial origin. PCR with AOB selective primers was combined with denaturing gradient gel electrophoresis to allow comparative analysis of the dominant AOB populations and the phylogenetic affiliation of the dominant AOB was determined by cloning and sequencing or direct sequencing of bands excised from DGGE gels. Different AOB were found within and between different reactors. All AOB sequences identified were grouped within the genus Nitrosomonas. Within the lab-scale reactors there appeared to be selection for a low diversity of AOB and predominance of a single AOB population. Furthermore, the industrial input in both effluents apparently selected for salt tolerant AOB, most closely related to Nitrosococcus mobilis and Nitrosomonas halophila. [ABSTRACT FROM AUTHOR]

In this paper, the treatability of strong wastes originating from anorganic chemicals industry was studied. Literature data were evaluated to assess the applicability of conventional and advanced methods of treatment to highly concentrated wastewaters. A detailed treatability study was conducted on the wastewater, which was provided from a small-scale polyester manufacturing plant. The manufacturing process involved only esterification reactions, generating a wastewater with aCOD content of over 200,000 mgl-1. The applicable treatment methods to be tested were determined as biological treatment of activated sludge process with low organic loading and chemical oxidation with H2O2. Results of the biological treatability study indicated that 80% COD removal could be obtained with 10 days retention time, provided that the system was fed with a 1/100 diluted raw wastewater. Chemical oxidation of raw wastewater with H2O2 in acid conditions and using ferric chloride as catalyst yielded 70% COD removal. However, the dosage required to obtain this efficiency was about 1 kg H2O2 per m3 of wastewater. With these applications the wastewater was treated to yield a COD of lower than 2000 mg/l. Results of the study were discussed and evaluated considering complexity and cost of treatment. [ABSTRACT FROM AUTHOR]

The performance of a bench-scale horizontal-flow anaerobic immobilized sludge (HAIS) reactor treating a synthetic substrate under increasing influent sulfate (SO42-) concentrations wasinvestigated. The synthetic substrate was composed of glucose, methanol and ammonium acetate, besides bicarbonate and trace metal nutritional solution. The reactor was filled with polyurethane foam cubic matrices for biomass immobilization. Influent chemical oxygen demand (COD) was kept almost constant along the experiments (2162 plus or minus 250 mg.l-1) while influent sulfate concentration was increased from 9 to 501 mg.l-1, resulting in COD/SO42- ratio of 249, 66, 19.7 and 4.3 in the four experimental phases tested. After a short start-up period, no significant variations in COD removal efficiency were observed for the COD to sulfate ratios evaluated. Although sulfate reduction was expected to interfere with the methanogenic process, detrimental effects on the overall reactor performance were not observed. Moreover, monitoring parametersindicated that the reactor achieved stable operational conditions immediately after short transient periods following the increase of influent sulfate concentrations. Microscopic analysis of the sludge within the reactor permitted to observe the presence of both methanogenicand sulfate reducing bacteria, indicating that syntrophism and not competition seemed to be the predominant relationship between these two groups under the COD to sulfate ratios assayed. [ABSTRACT FROM AUTHOR]

Discharge of aniline to the environment must be controlled as aniline is toxic to aquatic life and also exerts additional oxygen demand due to nitrification reaction involved during its biodegradation. Organic carbonaceous removal by heterotrophs during aniline biodegradation releases NH4+ which is the substrate for autotrophic nitrifying bacteria. However, aniline is toxic to nitrifying bacteria and severely inhibits their activity. Accordingly, batch andcontinuous studies were conducted to assess the biodegradation of aniline and its inhibitory effect on nitrification. Synthetic wastewater was used as feed with aniline as sole carbon source for mixed microbial population. Experiments were conducted at ambient temperatures of 30--32 deg.C. An aerobic activated sludge unit was operated at an HRT of about 13 hours and SRT of about 12 days. Biomass from aerobic activated sludge process treating domestic wastewater was acclimatizedto synthetic wastewater containing aniline. Removal efficiencies more than 95% were obtained for feed aniline concentrations up to 350 mg/l with insignificant inhibition of nitrification due to aniline. Ammonia oxidation rates of about 20--115 mgNH4N/l/d were observed. Batchtests were carried out to test the inhibitory effects of high initial aniline concentrations on nitrification. Carbonaceous removal by heterotrophs proceeded rapidly within 4--6 hours with nitrification picking up as soon as aniline concentration dropped below 3--4 mg/l. Forhigher initial aniline concentration more than 250 mg/l, complete nitrification did not take place even after aniline concentration dropped below 3--4 mg/l. ) 1997 IAWQ. Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]