Supercritical water oxidation for the destruction of toxic organic wastewaters:A review

The destruction of toxic organic wastewaters from munitions demilitarization and complex industrial chemical clearly becomes an overwhelming problem if left to conventional treatment processes. Two options, incineration and supercritical water oxidation （SCWO）, exist for the complete destruction of toxic organic wastewaters. Incinerator has associated problems such as very high cost and public resentment; on the other hand, SCWO has proved to be a very promising method for the treatment of many different wastewaters with extremely efficient organic waste destruction 99.99% with none of the emissions associated with incineration. In this review, the concepts of SCWO, result and present perspectives of application, and industrial status of SCWO are critically examined and discussed.

Start-up strategies of UASB reactor for treatment of pharmaceutical wastewater

Two start up strategies of upflow anaerobic sludge blanket(UASB) reactor for treatment of pharmaceutical wastewater were investigated. The results showed that both of them were workable. Compared with the strategy that started up the reactor directly using chloromycetin wastewater, the strategy that started up the reactor first using mixed wastewater and then using chloromycetin wastewater could save time by 23%. When the latter strategy was adopted the development of sludge activity fluctuated more largely and its final activity was lower, but the sludge grew faster in the course of start up.

Chloramination of wastewater effluent: Toxicity and formation of disinfection byproducts

The reclamation and disinfection of waters impacted by human activities（e.g., wastewater effluent discharges） are of growing interest for various applications but has been associated with the formation of toxic nitrogenous disinfection byproducts（N-DBPs）. Monochloramine used as an alternative disinfectant to chlorine can be an additional source of nitrogen in the formation of N-DBPs. Individual toxicity assays have been performed on many DBPs, but few studies have been conducted with complex mixtures such as wastewater effluents. In this work, we compared the cytotoxicity and genotoxicity of wastewater effluent organic matter（Ef OM） before and after chloramination. The toxicity of chloraminated Ef OM was significantly higher than the toxicity of raw Ef OM, and the more hydrophobic fraction（HPO）isolated on XAD-8 resin was more toxic than the fraction isolated on XAD-4 resin.More DBPs were also isolated on the XAD-8 resin. N-DBPs（i.e., haloacetonitriles or haloacetamides） were responsible for the majority of the cytotoxicity estimated from DBP concentrations measured in the XAD-8 and XAD-4 fractions（99.4% and 78.5%, respectively）.Measured DBPs accounted for minor proportions of total brominated and chlorinated products, which means that many unknown halogenated compounds were formed and can be responsible for a significant part of the toxicity. Other non-halogenated byproducts（e.g.,nitrosamines） may contribute to the toxicity of chloraminated effluents as well.

Non-thermal plasma treatment of Radix aconiti wastewater generated by traditional Chinese medicine processing

The wastewater effluent from Radix aconiti processing, an important step in the production processes of traditional Chinese medicine（TCM）, is a type of toxic wastewater and difficult to treat. Plasma oxidation methods have emerged as feasible techniques for effective decomposition of toxic organic pollutants. This study examined the performance of a plasma reactor operated in a dielectric barrier discharge（DBD） to degrade the effluent from R. aconiti processing. The effects of treatment time, discharge voltage, initial pH value and the feeding gas for the reactor on the degradation of this TCM wastewater were investigated. A bacterium bioluminescence assay was adopted in this study to test the toxicity of the TCM wastewater after non-thermal plasma treatment. The degradation ratio of the main toxic component was 87.77% after 60 min treatment with oxygen used as feed gas and it was 99.59% when the initial p H value was 8.0. High discharge voltage and alkaline solution environment were beneficial for improving the degradation ratio. The treatment process was found to be capable of reducing the toxicity of the wastewater to a low level or even render it non-toxic. These experimental results suggested that the DBD plasma method may be a competitive technology for primary decomposition of biologically undegradable toxic organic pollutants in TCM wastewater.