Papers by Keyword: Effluent

Abstract: Raw wool contains high percentage by weight of natural contaminants. It is usually treated by a scouring process in the first stage of textile processing. Wool scouring process consumes large quantities of fresh water and produces concentrated effluent with very high oxygen demand, aggravating the water resource shortage and environmental impacts. Water footprint (WF) is a multidimensional indicator that shows water consumption volumes by source and polluted volumes by type of pollution. This study discusses the environmental impacts assessment of wool scouring process based on the WF theory. Through cases study, it was found that chemical oxygen demand (COD_Cr) was the most critical pollutant associated with the largest pollutant-specific original grey WF (WF_{ori, grey}), while NH₃-N was the most critical pollutant associated with the largest pollutant-specific residuary grey WF (WF_{res, grey}). The average WF_{ori, grey} of wool scouring process was 51878 m³/d, approximately 291 times of blue WF (WF_blue). After treatment of the scouring effluent through floatation reflux-biological contact oxidizing technology, the WF_{ori, grey} reduced to 558 m³/d. Refluxing and regulating, oil removal were two important processes that contributed largely to effluent treatment as they reduced WF_{ori, grey} by 28537 m³/d and 23171 m³/d, respectively.

Abstract: In this study, the soil column experiment was adopted to investigated the release characteristic of P from soil by citric acid leaching. The results showed that the P release characteristics were different from each other under various citrate concentrations. At high concentration (50 mM) treatment, P concentration of effluents increased rapidly with effluent volume at the beginning, reached the maximum value after approximately 150 ml solution had passed through the columns. For the column treated with 5 mM of citric acid, the P in leachates was increased gradually to the maximum concentration, and then approached a relatively stable level during the 1000-3050 ml effluent volume. For low concentration (0.5 mM) treatment, the level of P in the effluents has always been very low, though a small peak was observed during the leaching.

Abstract: Arsenic contaminated soil is a serious worldwide problem nowadays, and soil washing technique is one of hottest topics in the area of remediating arsenic contaminated soils, while treatment of the washing effluent is still an urgent problem. In this study, in order to select the best washing extractants for arsenic contaminated soil of the Xiangxi Autonomous Prefecture, nine kinds of extractants (citric acid, oxalic acid, malic acid, tartaric acid, H₃PO₄, KH₂PO₄, KOH, NH₄Ac and ultra-pure water) were studied. Innovatively, a new material (calcined Mn-Fe Layered double hydroxide) was firstly introduced and fully applied to the adsorption of arsenic washing effluents. Results showed citric acid, oxalic acid and KH₂PO₄ were the optimal extractants for arsenic contaminated soil, considering the extraction rate and environmental perspective. When the concentrations were 200, 300, 300 mmol/ L , solution soil ratios were 10, 10, 20 mL/g , extraction times were 12,12,12 h, the citric acid, oxalic acid and KH₂PO₄, respectively, achieved the maximum extraction rate of 39%, 65% and 29%. Calcined Mn-Fe LDH used in this work was characterized by SEM and FT-IR, indicating the unique structure and high phase purity of the synthetic samples. For the 28mg/L arsenic effluent washing by citric acid, calcined Mn-Fe LDH showed the most effective capacity as adsorbent under neutral or weak base condition as well as 2 h absorption time.

Abstract: The transport of pathogenic bacteria from wastewater treatment facilities in subsurface has attracted extensive concerns over recent decades, while the impact of effluent water chemistry remains unclear. The influence of retention time in effluent from a municipal wastewater treatment plant on bacterial surface properties and deposition of Escherichia coli strains in saturated quartz sand packed-bed columns was investigated in this paper. Retentions in effluent significantly altered bacterial surface properties, such as zeta potential, surface charge and hydrophobicity, subsequently changed their deposition rate coefficients and attachment efficiencies in quartz sand packed-bed columns. Under low ionic strength conditions, bacterial deposition onto quartz sand grains was in agreement with the predictions of DLVO theory, in which the secondary energy minimum was demonstrated to be predominant.

Abstract: Based on the physical and chemical properties of carbide slag, the contents of heavy metals in effluent came from carbide slag drying process were studied, and then the composition of exhaust gas emitted from the carbide slag drying process and calcinations process of raw materials prepared with carbide slag was detected, in order to know whether there are harmful or corrosive gases released and the effect of the emissions on the environment and related equipments. The results indicate that the exhaust gases emitted from the calcination process of raw meal prepared with carbide slag is mainly composed of CO₂ and water vapor, and is free from harmful gases. However, a lot of water in carbide slag during the pre-heat and decomposition process under high temperature would accelerate the corrosion of equipments. Simultaneously, a small number of heavy metal ions contained in the carbide slag can cause environmental pollution and sulfides would be adverse to the cement calcination process resulting in the crust blockage of kiln.

Abstract: The hydroxy-aluminum pillared bentonite(OH-Al-bent) and aluminum pillared bentonite(Al-bent) were synthesized and characterized by XRD and SEM analysis. The yield of products and the adsorbent capabilities for Cr(Ⅵ) from aqueous solution were investigated, and the optimal experimental conditions including adsorption time, reagent dosage, the initial concentration of Cr(Ⅵ) and PH that might influent the adsorption performance were also investigated. It was observed that the adsorption capabilities of OH-Al-bent was better than Al-bent. The efficiency of Cr(Ⅵ) removal were better when the dosage of the sorbent was higher. And a reagent dosage of 7g/L, adsorption time of 60min, PH of 4 were selected as an optimum conditions.

Abstract: In this study, investigations were carried out to find the best possible way of lowering the concentration of suspended solids at the blast furnace gas scrubbing systems which have long been a problem in steel making industries. The analyses of the experimental results showed that the Bulab 5615 that is currently being used is the best possible chemical polymer. At very low concentration the chemical has shown its ability to reduce suspended solids to desired levels. The three other chemicals used required a much higher dosing rate. Experiment was also conducted on controlling the conductivity and to solve the issues of high COD, ammonia and phenols using a pilot bio-plant and reverse osmosis. This work will make the adhering to the policy implemented in 2006 of zero effluent discharge of the Department of Water and Forestry and contribution towards saving our water.

Abstract: In this paper, the process of cellulase pretreatment before alkali-oxygen pulping of bagasse was studied. The effect of cellulase pretreatment on subsequent pulping was also researched. The results showed that some small-sized components and sugars dissolved into the effluent in the process of cellulase pretreatment. UV spectroscopy showed that there was no significant lignin content in the pretreatment effluent.It was also found that pulping properties were promoted when the cellulase dosage was 2 ECU/g pulp, in that under the same cooking conditions, pulp kappa number was decreased by 1.3 and pulp brightness was increased by 2.5 %ISO, while the viscosity of pulp also increased slightly. Moreover, the tensile index, tear index and folding endurance were increased by 8%, 7% and 30%, respectively, but burst index showed no significant change. The above results illustrated that cellulase pretreatment was only beneficial to the dissolution of sugars and fine components from bagasse and it was an effective method of promoting alkali-oxygen pulping of bagasse.

Abstract: Using a multi-effect evaporation system to concentrate the effluent from alkaline peroxide mechanical pulping (APMP) plants is known to require a high energy consumption. In order to improve the situation, a polyethersulfone (PES) membrane was used to concentrate the effluent of APMP plants beforehand. An orthogonal experimental design was applied and a mathematical model was established to optimize the filtration parameters. An estimation of potential energy and water savings from this new concentration process was developed. The optimal filtration conditions obtained were: molecular weight cut-off at 10,000 Dalton, trans-membrane pressure at 3 bar, feed temperature at 50oC, cross-flow velocity at 420 rpm, and volume reduction factor at 0.93. The average permeate flux under these conditions was 45.31 l/m2.h. The total solids content was increased from 14.74 g/l in the feed to 95.04 g/l in the concentrate. The permeate had low total solid contents of 8.75 g/l, Chemical Oxygen Demand of 6696 mg/l, and Biochemical Oxygen Demand of 4383 mg/l. Such qualities would allow the permeate to be reused in the alkaline peroxide mechanical pulping process. With this new concentration process, about 4840.6 kWh energy can be saved and 23.3 m3 effluent discharge can be reduced for each ton of pulp produced.

Abstract: The moderate pollution load of APMP effluents provides a chance for a new treatment process--combination of biological pre-treatment and coagulation treatment. Biological pre-treatment can reduce the pollution load and produce biomass at the same time. The removal of COD was 60.22% and the yield of biomass was 7.12g/L at the optimized conditions treated by Aspergillus niger. And the removal of acid-soluble lignin and color were up to 60% and 42.57%. The coagulation treatment was applied after bio-treatment by using alum and PAM as coagulation agent. The conditions of coagulation were optimized in this article. The optimized conditions were: Dosages of alum and PAM were 1000-1200mg/L and 2mg/L, pH is 5, stirring time is 30S at 300rpm, the temperature is 50°C. The coagulation removals of COD, color and turbidity were 83.80%, 86.38% and 98.33%. The removals of color were characterized by absorbance of 465nm, 325nm, 275nm and 254nm.