Study On Pretreatment Processes For Wastewater Of C₉Petroleum Resin

The C9petroleum resin wastewater contains complicated compositions, high pH value, toxicity compounds, making it difficult to biodegrade. Furthermore, most toxic organic compounds can be accumulated in organisms, posing a threat to human health and environments. Therefore, a pretreatment must be taken to reduce the toxicity, improve the biodegradability and decrease the concentration of organic pollutants for the post-treatment processing.In this study, wastewater samples from a C9petroleum resin production company were taken, and pretreatment techniques, such as Fe/C process (Ferric-carbon micro-electrolysis process), Fe/C-H2O2technology (the combination of ferric-carbon micro-electrolysis process and Fenton reagent), O3/H2O2oxidation technology (ozone-hydrogen peroxide) and O3/H2O2-Fe/C technology (the combination of ozone-hydrogen peroxide and ferric-carbon micro-electrolysis process), were applied to treat the wastewater. The organic compounds in the C9petroleum resin production wastewater and the effluent (from the treated wastewater by the above methods) were analyzed by Gas Chromatograph-Mass Spectrometer (GC-MS). The main results were concluded as follows.1. The pretreatment of C9petroleum resin wastewater via the Fe/C process and Fe/C-H2O2technology.(1) The optimal parameters of Fe/C process were obtained as follows. The mass ratio of iron (Fe) to activated carbon particles (C) was2:1(w/w) with Fe dosage of30g·L-1. The pH, reaction time and aeration rate were5,1.5h and2.0L·min-1, respectively. The removal rates of CODCr (chemical oxygen demand) and TOC (total organic carbon) were 39.8～41.7%and32.4～35.1%, respectively. The B/C ratio (BOD5to CODCr) was improved up to about0.31-0.34.(2) The optimal parameters of Fe/C-H2O2process were obtained as follows. The pH value was5, the dosage of H2O2was5mL·L-1and adding mode was2mL·L-1H2O2initially, then3mL·L-1H2O2for1.5h, and the total reaction time maintained3h. Eventually, the removal efficiencies of CODCr and TOC were62.0～65.0%and44.2～45.1%, respectively. The B/C ratio was changed up to about0.52～0.54.(3) The continuous operation optimal parameters of Fe/C-H2O2process were obtained as follows. The hydraulic retention time was40min in the Fe/C processing. The dosage of H2O2of5mL·L-1and the hydraulic retention time of10min were obtained in Fenton processing. The removal efficiencies of CODcr and TOC were58.7～63.2%and38.9～42.4%, respectively. The B/C ratio was improved up to about0.47～0.53.(4) Soaking with a6%H2SO4solution did good to maintain the treatment effect of the micro-electrolysis materials. And the micro-electrolysis materials were washed every8h with the total use time less than112h.2. The pretreatment of C9petroleum resin wastewater via the O3/H2O2process and O3/H2O2-Fe/C technology.(1) The optimal parameters of O3/H2O2process were obtained as follows. The dosages of O3and H2O2, pH, hydraulic retention time were2.5L·min-1,7mL·L-1,11and25min, respectively. During continuous operation treatment of C9petroleum resin wastewater, the removal rates of CODCr and TOC were35.3～35.8%and14.4～19.7%, respectively. The ratio of B/C was0.50～0.52. However, it didn’t meet the advance requirements of the sewage treatment plants because the average CODCr values (1058mg·L-1) in the effluent were higher than800mg·L-1.(2) The results of the single-factor and the orthogonal test showed that O3/H2O2system can be used in the pretreatment of C9petroleum resin wastewater regardless of the pH value.(3) Experimental result indicated that Fe/C process pretreatment following the O3/H2O2process was the best operation of O3/H2O2-Fe/C process. When Fe/C process and O3/H2O2oxidation technology were combined, the removal rates of CODcr and TOC were64.9～67.3%and69.2～70.7%, respectively. The B/C ratio was0.50～0.55.3. By comparison of various results of continuous processing for C9petroleum resin wastewater, it was found that O3/H2O2-Fe/C technology is the best pretreatment of this water. 4. The GC-MS was used for the characterisation of organic materials in C9petroleum resin production wastewater and the out-let water. The results showed that the main organic compounds were phthalic acid esters, sulfurous esters, ketones, chlorobenzene compounds, various alcohols, derivates of indene, derivates of indene, benzene derivatives and some hetero atomic compounds contains atomic such as sulphur, nitrogen, silicon. In the treatment of Fe/C process, the amount of larger molecular pollutants were transformed into small molecules such as alcohols, terpenes, aerobic containing alkanes, imidazole, benzene homologues, aldehydes and olefin. In the pretreatment by the Fenton reagent and O3/H2O2technology, the organic materials were degraded or transformed into some small molecule alcohols, aerobic containing alkanes, terpenes, thiophene, imidazole and olefin. And in the pretreatment by the O3/H2O2-Fe/C technology, the organic materials were degraded or transformed into some small molecule alcohols, aerobic containing alkanes, terpenes, imidazole and olefin. It should be noted that2-ethyl-l-hexanol was the predominant product in these four treatment process.