Using the EDTA Hole Scavenger to Accelerate Decolorization in the Immobilized Photocatalytic Process

This study investigated the effect of EDTA as a hole scavenger on accelerating the photocatalytic decolorization of direct blue 71 as a non-degradable model pollutant with nano TiO2 powder immobilized on a cementitious bed. For this purpose, 75 mg/L of the dye was decolorized in 75 minutes with 0.03 M of EDTA at a pH level of 6 and under irradiation produced by a 60-W UV-C lamp. This is while decolorization under identical conditions but in the absence of EDTA had been accomplished in 225 minutes. The experiment, therefore, confirmed the accelerating effect of the scavenger on decolorization. The kinetics of the photocatalytic process with EDTA followed a first order reaction with a constant rate of 0.05 min-1, which is 2.5 times faster than the process without EDTA

Investigation of Dye Removal Efficiency of the Photoelectrocatalytic System Using Graphite and Stainless Steel as Electrodes

The removal of Acid Orange 7 by the photoelectrocatalytic process was investigated at ambient temperature under solar irradiation using graphite as the cathode and stainless steel coated with the ZnO/TiO2 nanocomposite as the anode. The microstructure of the ZnO/TiO2 coated electrode was characterized by the SEM test. The results revealed dye and COD removal efficiencies of 99% and 97%, respectively, over a period of 360 minutes. The best performance was achieved in 360 minutes with no aeration at a current of 1 mA/cm2, an initial dye concentration of 100 mg/L, an electrode surface area of 30 cm2, and an electrolyte concentration of 0.01 M; energy consumption under these optimum conditions was 0.15 KWh/ppm. It may be concluded that the photoelectrocatalytic process is well capable of removing organic compounds, especially textile effluents containing dyes and non-degradable contaminants, due to its ability to produce hydroxyl radicals, superoxide, etc. Thus, the technique may be recommended for use as a pre-treatment process to reduce operational costs

SBAR Capability for Methyl Tertiary Butyl Ether Removal: Characterization of the Bio-granules

The growing use of MTBE as a substitute for Tetraethyl lead and its adverse impacts on the environment warrant its removal from wastewater. Given the low efficiencty and the high cost associated with the chemical and physical processess commonly used for the removal of MTBE, which also release hazardous by-products into the environment, biological techniques have been explored as the more appropriate methods for its removal. This research seeks to investigate the feasibility of the SBAR system and aerobic biogranules for MTBE removal. For this purpose, a synthetic wastewater containing the materials needed for the microorganisms was used for the experiments and the pH level and DO were set to 7‒8 and 2‒5 mg/L, respectively. TEM was employed to characterize the granules. Results showed that over 90% of the initial COD (500 mg/L) was removed after 4h, which was attributed to the air stripping (28%) and sorption (1.5%) mechanisms. The resulting granules were brown in color, 2‒6 mm in size with a mean fall speed and a density equal to 0.65 cm/s and 0.055 g/ml, respectively. The superiority of the resulting granules to the flocs led to improved sedimentation in the reactor. Finally, TEM investigations showed that the sylyath and rotifer species formed the dominant populations in the granules

Determine the Optimum Conditions for Acid Red 14 Removal by Iron Nanoparticles Modified with Nickel in a Slurry System

In this study, bimetallic iron–nickel nanoparticles were obtained by chemical co-deposition of iron chloride with sodium boron hydride used as a strong reducing agent. The bimetallic nanoparticles thus obtained were then used to remove acid red 14 in a slurry system. Experiments were conducted to investigate such parameters as initial dye concentration, nano-particle dosage, pH, the time required for the nano-particles to be used after they are formed, the stirring speed, and the temperature required to reach optimum reaction conditions. Control experiments were subsequently performed under the optimum conditions thus determined to identify any other remaining factors involved. The optimum conditions included a temperature of 25±2 ºC, a newly synthesized nano-particle concentration of 0.05 g/L, an initial dye concentration of 200 mg/L, a pH level of 7.5, and a mixing duration of two minutes. The results indicated the high activity of the nanoparticles such that removal efficiencies equal to 79.39, 90.52, and 94.42 percent were achieved after 2, 30, and 240 minutes, respectively. Moreover, a COD removal of 72.61 percent was achieved after 4 hours of reaction

Removal Mechanisms Involved in the Petroleum Refinery Wastewater Treatment by MBBR System

Effluents bearing petroleum hydrocarbons must be treated prior to release into the environment due to the high toxicity of these compounds and the consequent hazards they pose to the receiving environment. The moving bed biofilm reactor (MBBR) is one of the several biofilm systems used in treating different types of wastewater that offers a good resistance to both toxic and hydraulic shocks. This study investigates the roles of the three air stripping, adsorption, and biodegradation mechanisms in the biofilm reactor using polyethylene sponge strips used as the biomass to treat the effluent from Tehran Refinery. Results and discussion: Based on the results obtained, the optimum values of loading rate, retention time, and media filling ratio were equal to TPH=278 mg/L (COD=1000 mg/L), 22 hours, and 50 percent, respectively. Laboratory studies confirmed that each of the three mechanisms of air stripping, adsorption, and biodegradation may be involved in the removal of petroleum hydrocarbons by the MBBR system depending on hydrocarbon concentrations. More specifically, biological degradation was the dominant removal mechanism with lower loading rates (TPH=57 mg/l with a COD equal to 200 mg/l) while stripping became the dominant mechanism at higher loading rates (TPH=278 mg/l with a COD equal to 1,000 mg/l). It was found that under optimum conditions and at TPH=278 mg/L (and COD=1,000 mg/l), stripping removed 58%; biodegradation, 29%; and adsorption, 13% of the petroleum hydrocarbon content. It was observed that the removal of petroleum hydrocarbons by stripping and adsorption processes took place within the first process hour at the latest

Study of Phytoremediation Capability in Sulfate Removal from Water

Phytoremediation is known as a pollutants method with low cost, without operational complexity, with low energy consumption and no need for sludge disposal. In this study, hydroponic cultivation was chosen for estimation of sulfate removal as a significant sulfur compound in effluents on two fenny plants: pampas grass and bamboo.In this case, the plants were examined under two different retention times and after determining the optimum time (7 days), the main experiments were done for evaluating the plants removal efficiency and sulfate mass absorbance by plants. For better analysis, T-Test and ANOVA with significant influence (p < 0.05%) were also done. Finally, the removal efficiency in pampas grass for all concentrations of 50, 200, 300, 600, 900, 1200, 1500 and 3000 mg/L were 44, 36, 34.22, 30.55, 15.93, 9.72, 7.77 and 4.44 percent, respectively, which were up to two times higher for the bamboos

Reuse of Sewage Sludge for Agricultural Soil Improvement (Case Study: Kish Island)

Sludge from wastewater treatment plants is a valuable source of nitrogen, phosphorus and potassium which are necessary for the plants growth. The purpose of this research was to control sludge quality to use it for soil improvement in Kish Island, Iran. Because of soil with low qualified for agricultural activities and high import expenses of fertile soils from outside of the Island, application of sludge as a cheap source of soil amendment is an easy and economical mean to improve the soil in KishIsland. Comparison of laboratory data of domestic sludge with global standard has shown that it has suitable for application on landscapes and agriculture from the point of view of fertility and heavy metals concentration. Biological data has also shown that the sludge was in class A or B of EPA standard, to fecal coliform, based on the ambient conditions such as water, air, temperature, sun radiation and storage time. The soil test data indicated that salinity, sodium and calcium ions were between 5000-7000 mg/kg which cause a decrease in plant's growth. Transplanting of garden petunia in the region has been done in different samples mixed with sludge rate of 0, 25, 50, 75 and 100 ton/ha during December 2008 to March 2009. In the first period of the growth study, the results have shown a decrease in the amended soil with sludge retard in comparison with control plant, but after 5 months probably because of spring rains and decrease in the salinity of amended soil, the plant has shown very good growth in leaves and petal, whereas the control plant was dried. Soil and plant analyses were also approved the results because physical (humidity increase) and chemical (EC decrease) characteristics of the amended soil with sludge were improved. Most of the time, the concentrations of micro-nutrients such as iron, manganese, zinc, copper and nutrients in soil and leaves showed an increase in values by an increase in the rate of applied sludge. Other results were not shown considerable variation in accessible phosphorus but noticeable decrease in potassium. Of course, in some special cases, negligible changes in cadmium and lead concentrations of the plant have been observed. In addition, the soil phosphorous content had negligible changes and the soil potassium content had a decreased rate in the amended soil. Finally, it is concluded that for sludge application, it is necessary to check agronomic nutrients levels and heavy metals accumulation. However it is also recommended to use any kind of salt resisted native plants for landscapes. In case of sensitive plant, sludge should be added at least 6 months in advance to ensure that soil physical and chemical condition are achieved

Evaluation of Advanced Oxidation Processes for Removing Acid Red 14 Dye from Aqueous Solutions

In this article, the degradation efficiencies of UV/TiO2, UV/H2O2, and UV/O3 processes are compared in the removal of Acid Red 14 which is the most commonly used dye in the textile industry. Results show UV/TiO2 recorded a degradation efficiency of above 90% in 30 minutes (pH=3, [Dye]=40mg/L, [TiO2]=400mg/L), UV/H2O2 degraded 75mg/L of dye (a degradation efficiency of more than 90%) in 160 minutes, and the efficiency of UV/O3 was above 95% in only 15 minutes using an ozone concentration of 0.9gr/h ([Dye]=250mg/L, pH=9). Judging on their high efficiencies, the use of these processes is recommended for the treatment of textile effluents. It may be noted, however, that the two processes of UV/H2O2 and UV/O3 are effective in both dye degradation and COD removal, but UV/O3 is costly and needs especial equipment. UV/TiO2 is not effective in COD removal and requires the post-treatment separation of nano-particles (using a centrifuge or sedimentation process). Thus, the UV/H2O2 process seems to be the easiest and most effective process in the treatment of textile effluent due to its simplicity and effective COD removal in a short time

Treatment of Wastewater Containing Aniline Using a Moving Bed Biofilm Reactor (MBBR)

In this research, the capability of the moving bed biofilm reactor (MBBR) for the treatment of aniline wastewater has been investigated. This compound is found in effluents from chemical, dye, pigment, herbicide, pharmaceutical, plastic, and paint industries. The moving bed biofilm reactor was developed to adopt the best features of the activated sludge process as well as those of the biofilter processes. In this study, a cylindrical moving bed biofilm reactor with an approximate capacity of 5 liters was used. The effects of LECA (Light Expanded Clay Aggregate) filling ratio and retention times (RT) of 8, 24, 48, and 72 hr were investigated on removal efficiency for different influent COD values. The best removal efficiency of 91% was obtained for a COD level of 2000 mg/L after 72 hour. Other experiments were conducted to evaluate the removal efficiency of the reactor under a decreased carrier volume of 30% and under continuous loading. NMR test results confirmed the capability of the reactor in the biodegradation of aniline. The capability of the reactor was also evaluated by feeding an organic shock that resulted in satisfactory performance of MBBR. The results showed that Grau and Stover-Kincannon were the best models to describe the biological kinetic data in this study

Lab Scale Study of Nitrate Removal By Phytoremediation

The purpose of this study was to Cultivate three suitable emergent herbaceous species (reed (Phragmites australis), bamboo (Dracaena sanderiana), and umbrella plant (Cyperus alternifolius)) in laboratory scale using hydroponic method and to examine their potential in removing nitrate from contaminated water. Three containers with initial NO3--N concentration of 15, 20, 25 mg/L, one container of perfect omex fertilizer and the last one with plane water and soil were used in this study. The variations of nitrate concentration, its removal rate, and plant growth (dry and wet weight) were all measured during 8 months of the study. The experimental results indicated that reeds had higher ability to remove nitrate as compared to bamboo and umbrella plant. For the highest concentration, reeds, bamboo and umbrella plant absorbed about 95, 85 and 70 percent nitrate, respectively. There was a direct relation between dry weight and removal efficiency and the most amount of nitrate absorption was measured in root and rhizome of the plant