Search

An iron and manganese species immobilization technology was developed in a fluidized bed reactor (FBR) with a new fluidized media, immobilized iron oxide (namely FeO x -30). The FeO x -30 catalyst exhibited excellent performance as a catalyst for the oxidation of Mn 2 + . About 95% and 30% of the manganese species were immobilized on FeO x -30 and silica sand in FBR, respectively. The oxidation rates of Fe 2 + and Mn 2 + and the immobilization efficiencies of iron and manganese oxides strongly depend on pH value. Usually during oxidization the pH values of the solution containing Fe 2 + must be above 7, and Mn 2 + must be above 9. During this study, large amounts of iron species leached from the surface of FeO x -30 only when manganese was in the system. The surface of the FeO x -30 became fragile in a single system. However, the removal of iron and manganese species simultaneously was better than only the removal of manganese in an FBR. In the binary system, the optimum pH condition for immobilization of both iron and manganese species was pH i 9. The higher catalyst loading in the binary system led to a higher removal efficiency of iron and manganese.

Phosphorus chemicals control key aspects of eutrophication and other environmental process. Hypophosphite (HP) originating from manmade and natural sources was evidenced as present in the environment and was investigated rarely. Recently, iron oxide has been used as a catalyst for oxidising organic contaminants with hydrogen peroxide (i.e. heterogeneous Fenton-like reaction). This study focused mainly on the oxidation of 1.0 mM HP by hydrogen peroxide in the presence of a novel iron oxide catalyst (B1 catalyst) which was prepared through a fluidised-bed Fenton reactor (FBR-Fenton). The background experiments including the oxidation experiment of HP by air only, by H2O2 only and adsorption of HP by B1 catalyst were first elucidated. It was found that HP could not be oxidised at all by air and H2O2 at pH 2.5–12 in 24 hours. On the other hand, it could be adsorbed by B1 catalyst with 89.8% removal at pH 2.5 in 5 hours and complete desorption at pH 11.0. Then, we investigated the effects of pH and Fe leaching from the catalyst on the oxidative efficiency of HP. We found that although the removal rate of HP at pH 2.5 is faster than that at pH 4.0, B1 catalyst has a higher HP oxidation efficiency at pH 4.0 than that at pH 2.5. We conclude that it is a major heterogeneous catalytic oxidation by our novel iron oxide catalyst to oxidise HP at pH 4.0. Also, B1 could be a useful and potential catalyst for the treatment of HP wastewater.

A novel electro-Fenton method, called the Fered-Fenton method, applying H2O2 and electrogenerated ferrous ions for treating organic-containing wastewater was investigated. By combining electrochemical reduction and chemical oxidation, the process can regenerate ferrous ions and remove organic compounds simultaneously in a batch reactor. Because the generation rate of ferrous ions is one of the key parameters in evaluating the oxidation efficiency of the reaction system, the initial current efficiencies (ηi) for iron (III) reduction are examined first. It shows that increasing initial ferric ion concentration can achieve high initial current efficiency. In addition, ηi decreased (ca. 20-100%) with increasing current density of cathode (ca. 40-199 A/m2). For illustration, the wastewater from chemical (i.e. electroless) nickel plating was treated in this investigation owing to its non-biodegradability and high organic concentration. The average pH, COD and Ni concentrations of this wastewater were about 5.0, 30,000 and 2,000 mg/L, respectively. Experimental results indicate that traditional Fenton method only removed 60% of COD when using 5,000 mg/L of ferrous ions. However, the COD removal efficiency was promoted after the electricity was introduced into the system (i.e. Fered-Fenton method). Moreover, Ni concentration was reduced from 2,080 to 0.3 mg/L, indicating that the removal efficiency was higher than 99.9%.

This study investigates the influence of organic shock loading on H2 production in an upflow anaerobic sludge bed (UASB) reactor. An esterification wastewater produced from a polyethylene terephthalate (PET) manufacturing plant was applied; the major organic pollutants are ethylene glycol and acetaldehyde. Experiments of two influent modes were performed here: a continuous-flow mode with a step input of shock loading and a batch mode with a pulse input of shock loading. Results of the continuous-flow experiments indicate that biogas production parameters such as H2 concentration and biogas production rate are more sensitive than water quality parameters such as pH, ORP, COD and TOC. In particular, H2, increasing by 140% within 1 hour, is a very important index upon the organic shock loading. It changes from 120 ppm to over 600 ppm as the organic loading rate increases from 4.4 to 13.2 kgCOD/m3·day through 4 hours of shock loading. Experiments of the batch shock loading with different pulse dosagesof ethylene glycol, acetaldehyde and the raw wastewater were also investigated. The amount of H2 production increased in proportion to an increase of organic load. Furthermore, the sequence of H2 production among the three types of shock loading is acetaldehyde> ethylene glycol> raw wastewater. To sum up, H2 shows a faster response rate than the other parameters. Therefore, H2 can be adopted as an important parameter for organic shock loading in UASB.

The electro-Fenton method, in which ferrous ion is produced at the anode and used as a catalyst of H2O2, was applied for treating the bioeffluent of petrochemical manufacturing wastewater. The major pollutant in the bioeffluent was identified as hexamine, which was nonbiodegradable and contributed 65% of COD. The goal of this study was to treat the biotreatment effluent with more than 50% of COD removal efficiency. Oxidants that involved ozone, ozone/H2O2, sodium hypochlorite, and Fenton's reagent were employed to treat this effluent by jar tests. However, none could meet the goal in the range of operating conditions used. On the other hand, more than 80% of COD was removed with the electro-Fenton process. These screening tests indicated that only the electro-Fenton process was compatible with the goal.