Enhanced Treatment Of Reverse Osmosis Concentrated Water By Ozone Based Advanced Oxidation Processes

Reverse osmosis technology has developed rapidly and is widely used in industrial wastewater treatment and reuse sections in recent years.But the treatment of resulting reverse osmosis concentrates（ROC）has become one of the current challenges for industrial waste water treatment because of the high salt content and difficulty in degradation of organic pollutants.In the present work,three types of ozone based advanced oxidation processes,including catalytic ozonation,ultraviolet/ozone coupling technology and peroxone,were used as treatment methods for two different reverse osmosis concentrated from two steel companies（1#ROC was effluent of membrane desalination from integrated wastewater in one steel plant;2#ROC was effluent of membrane desalination from coking wastewater in other steel plant）.To enhance its activity in catalytic ozonation,the biochar from pine and other softwood shavings was calcined under nitrogen,hydrogen and ammonia atmosphere,respectively.Among them,the biochar modified by ammonia had the best catalytic activity,followed by hydrogen,and the modification effect of nitrogen is the worst.Temperature Optimization results of ammonia calcination showed that 500℃ was the optimal condition.According to the characterization results of catalysts,there was nitrogen doped on the biochar after calcining under ammonia atmosphere and the relative proportion of pyrrole-like nitrogen in the doped nitrogen element is positively correlated with the degradation effect of reverse osmosis concentrated.Two different reverse osmosis concentrated were treated by UV/O₃ coupling and peroxone technology.After optimization of operating parameters,the degradation of two reverse osmosis concentrated by UV/ozone coupling technology was better than peroxone.The total organic carbon（TOC）removal rate of 1#ROC and 2#ROC within one hour was 72.2%and 59.4%,respectively（the organic polutants content of both water samples meets the latest industrial wastewater discharge standards）.The TOC removal rate of two reverse osmosis concentrated within one hour treated by peroxone was 63.1%and 33.6%.2#ROC was more difficult to degrade than 1#ROC in both UV/ozone coupling process and peroxone process,which was probably because that the 2#ROC contains more refractory soluble microbial metabolites.Further analysis of inorganic ion concentration in two ROC indicated that the concentration of chloride and sulfate ions in 2#ROC were much higher than that in 1#ROC.Then the concentration of inorganic ions in ROC were adjusted and the degradation experiments were carried out.The results showed that sulfate ions could inhibit the treatment of ROC by peroxone technology.It probably because sulfate ions have an inhibitory effect on the active species hydroxyl radicals during the degradation.