TOC Removal Ratio Research Articles

Hydrolyzed polyacrylamide biodegradation and mechanism in sequencing batch biofilm reactor

An investigation was performed to study the performance of a sequencing batch biofilm reactor (SBBR) to treat hydrolyzed polyacrylamides (HPAMs) and to determine the mechanisms of HPAM biodegradation. The mechanisms for the optimized parameters that significantly improved the degradation efficiency of the HPAMs were investigated by a synergistic effect of the co-metabolism in the sludge and the enzyme activities. The HPAM and TOC removal ratio reached 54.69% and 70.14%. A significant decrease in the total nitrogen concentration was measured. The carbon backbone of the HPAMs could be degraded after the separation of the amide group according to the data analysis. The HPLC results indicated that the HPAMs could be converted to polymer fragments without the generation of the acrylamide monomer intermediate. The results from high-throughput sequencing analysis revealed proteobacterias, bacteroidetes and planctomycetes were the key microorganisms involved in the degradation.

Ferrous ions (Fe2+) assisted air-bubble cavitation degradation of organic pollutants

The ferrous ions (Fe2+) assistant air-bubble cavitation degradation of some organic dyes (Congo Red, Rhodamine B, Methyl Orange, and Methyl Violet) induced by air bubbles passing small glass balls was systematically investigated. Meanwhile, the influence of five operating factors, including air-bubbling time, FeSO4 ·7H2O amount, dye initial concentration, glass ball diameter, and gas flow rate, on the degradation of Congo Red dye were reviewed. Moreover, the degradation process of Congo Red is inspected by using UV–Vis, TOC, and HPLC techniques. It was found that the highest TOC removal ratio (81.42 %) was achieved under optimal conditions. On the other hand, the production and existence of ·OH radicals was testified through the oxidation of 1,5-diphenylcarbohydrazide (DPCI) forming diphenylcarbazone (DPCO). It can be inferred that the air-bubble cavitation induces ferrous ions to provide additional hydroxyl (·OH) radicals, which results in a rapid oxidation of organic dyes. Furthermore, the possible degradation process and mechanism were also discussed. All results demonstrate that this new degradation method has many advantages, such as high efficiency, energy savings, producing no secondary pollution, and being a simple device. Thus, it is expected to be feasible and promising as an advisable choice for the treatment of organic wastewater in the future.

Degradation of Acidic Congo Red via Activated Potassium Persulfate by Sunlight and Ferrous Ion

t was discovered that sunlight/Fe2+/S2O82- method is superior to UV/Fe2+/S2O82-method when we treated water samples of acidic Congo red .Congo red dye was applied in activated potassium persulfate by sunlight/ultraviolet and ferrous ion system investigation. It showed efficient sunlight/ultraviolet activated degradation of acidic Congo red, and the activation of sunlight was better than that of ultraviolet. The effect of pH value, Fe2+ and S2O82- concentration on the degradation of Congo red were investigated. The result indicated that when pH was 3.0, [Fe2+] was 0.42mmol/L, [S2O82-] was 74.0mmol/L, the decolouring ratio of acidic Congo red were 91.0% and 100% respectively after 5min and 60min of reaction times, the TOC removal ratio was 80.4% after 120min.

Experimental design methodology applied to electro-Fenton treatment for degradation of herbicide chlortoluron

The degradation of herbicide chlortoluron in aqueous medium by electro-Fenton process using a carbon felt cathode and a platinum anode was studied. The great oxidation ability of this process is due to the large production of hydroxyl radical (OH) by electrochemically induced Fenton's reagent. Hydroxyl radicals are very powerful oxidizing agents which react on organics up to complete mineralization. The influence of some experimental parameters such as initial concentration, current intensity and processing time on the degradation and mineralization rate of chlortoluron by hydroxyl radicals has been investigated. The evolution of chlortoluron concentration with processing time shows a pseudo first order kinetics (kabs=(4.8±0.2)×109mol−1Ls−1). A Doehlert matrix was applied for determination of the optimal working conditions. Optimal parameters for maximum mineralization efficiency (TOC removal ratio of 98%) was achieved after 8h of treatment using a chlortoluron initial concentration of 0.125mM and an applied current of 300mA. The mineralization of aqueous chlortoluron solutions was confirmed by identification of the end-products such as carboxylic acids and inorganic ions. Their evolution during electro-Fenton treatment was studied.

Studies on Saccharin Removal from Simulated Wastewater by Combined Ultraviolet Light Irradiation with Activated Carbon Adsorption

The present study is concerned with the application of UV light irradiation as the pretreatment method of activated carbon adsorption of saccharin from aqueous solution. For the purpose of improving the efficiency of saccharin removal from water, UV light irradiation was followed by subsequent activated carbon adsorption. Then, the results of saccharin removal between the two cases : activated carbon adsorption combined with UV light irradiation pretreatment and activated carbon adsorption alone, were compared.As the result, it was found that the removal ratio of 43 % at equilibrium state of activated carbon adsorption was increased to 67 % when saccharin solution was pretreated by UV light irradiation for 30 min in the air. The removal ratio of saccharin was kept at 87 % by UV light irradiation only for 180 min in the air, when activated carbon adsorption was not employed. But, the removal ratio of saccharin became almost 100 %, when activated carbon was employed after pretreatment of UV light irradiation of 180 min.Further, the TOC removal ratio obtained only by UV light irradiation of saccharin solution was 26 % after 180 min UV light irradiation in the air. However, the TOC removal ratio after 16 h activated carbon adsorption of saccharin solution was increased to 73 % when saccharin solution was pretreated with UV light irradiation for 180 min in the air.

Novel synergic combinatorial photoelectrochemical technology for degradation of trace of 2-chlorophenol in drinking water

Novel combinatorial photoelectrochemical (CPE) technology with combination of ultraviolet (UV)-photolysis and direct current (DC) electrolysis is studied and discussed for drinking water purification. In the self-made compositive photo-electrolysis incorporate reactor, removal rate of the 2-chlorophenol as model environmental pollutants has been investigated experimentally in terms of applied voltage, pH value, flow velocity, temperature, and aeration conditions. A. primary analysis of the combinatorial photoelectric synergic effect on the degradation of organic pollutants has been carried out. It is found that the best performance of CPE oxidation is achieved by the following conditions: DC voltage of 5.0 V combined with UV−254-raidation, near neutral of pH 8 with aeration of pure oxygen. The influences of circular velocity, temperature, and initial concentration of the pollutant are minor. Under the optimal conditions, removal ratio of 2-CP is higher than 50% in 30 min, and 100% removal ratio of 2-CP (5 × 10−6) can be reached and TOC removal ratio reached above 90% in 2.5 h. Complete mineralization is achieved eventually. It shows in our investigation that under the studied conditions the synergic effect of UV photolysis and DC electrolysis on the degradation of the model pollutant is remarkable and validated, which may be derived from the coexistence of mutual complementary mechanisms of photoelectrochemical action, and the radicals chain reactions resulted from photo activation and electrolysis excitation in the process of CPE oxidation.

Effects of C/N, C/S and S/N ratios on TOC and nitrogen removal in the sulfate reduction-sulfur denitrification process

Effects of C/N, C/S and S/N ratios on TOC and denitrification removal were examined in the sulfate reductionsulfur denitrification process using the two upflow biological filter reactors. High TOC and nitrogen removal ratio was obtained at C/N=2.2 and S/N=0.7 through the reactors. In the first reactor, sulfate reduction occurred predominantly. SRB mainly produced acetate at C/S=3.1. However, acetate was decomposed in the first reactor at C/S=1.6. In the second reactor, sulfur denitrification and heterotrophic denitrification occurred simultaneously. Sulfur denitrification occurred in the lower part of the reactor in S/N=0.7, and all sulfide produced in the first reactor was re-oxidized. On the other hand, sulfur denitrification also occurred in the upper part of the reactor in S/N=1.3, and 35 mg/gSS of sulfur granules were accumulated in the biofilm. The sulfur granules played an important role on denitrification. The activity of SDNB in the second reactor was about 3-4 times lower than the activity of DNB. When the S/N ratio increased, the activity of SDNB increased and those of DNB decreased. The number of SDNB was greater than those of DNB. The activity of SRB in the first reactor increased, when S/N ratio increased. SRB also grew in the anoxic second reactor, and the activity of SRB in the second reactor was relatively high. The sulfur cycle consist of sulfate reduction and sulfur denitrification in the second reactor might be established in the reactor.

生物活性炭による河川水からの有機物除去効果の長期変化

In this study, actual river water, that was pretreated by coagulation sedimentation, was treated in a fixed bed mini-column of biological activated carbon (BAC) or sand for a very long term about 1,800days, and the changes of effects to remove organic compounds by biodegradations and adsorption were investigated. In sand column which has only biodegradation effect by biofilm, 34% of organic compounds as TOC could be removed after one or two months of lag time. Biodegradation of organic compounds which had adsorbed once in pores brought about the extension of adsorption ability of BAC, and pore volume was recovered. Adsorption ability decreased with pore volume decrease by adsorption of organic compounds which were hardly degradable, and TOC removal ratio of BAC decreased gradually and became as same as that for sand after a long time.