Abstract
Investigations were conducted to examine the effects of amine type and initial concentration, free chlorine concentration, UV light intensity, pH and tert-butyl alcohol (TBA) on the formation of dichloronitromethane (DCNM) under UV/chlorine. Methylamine (MA), dimethylamine (DMA) and poly-dimethyl diallyl ammonium chloride (PolyDADMAC) were selected as the amine precursors of DCNM. And the reaction products of amines were explored through observing the contents of various nitrogen under UV/chlorine. Experimental results indicated that the higher of the intensity of UV light, the concentration of amines and free chlorine, the greater of the amount of DCNM formation; the amine substance with simple structure is more likely oxidized to form DCNM, so the potential of MA to form DCNM is the largest among three amines; the formation of DCNM decreased with increasing pH from 6.0 to 8.0; due to adding TBA into the reaction solution, halogen and hydroxyl radicals were restrained which resulted the DCNM formation decreased. In the reaction process, the formation of DCNM from amines increased at the beginning, then decreased and almost disappeared due to photodegradation. During the formation and photodegradation of DCNM, the dissolved organic nitrogen could be transformed into the ammonia-nitrogen (NH3-N) and nitrate-nitrogen (NO3−-N).
Highlights
In the past 10 years, more and more attention has been paid to the safety of drinking water supply
Other studies showed that the formation of N-disinfection by-products (DBPs) was related to the chlorination of natural organic matter (NOM), and UV treatment can degrade NOM into lower molecular weight products, which could react with chlorine or chloramine to promote the formation of DBPs5,26–29
In order to investigate the DCNM formation potential of amine precursors, the solutions of MA, DMA and PolyDADMAC containing the organic nitrogen of 0.5, 1.0 and 1.5 mmol/L were prepared for the experiments, respectively
Summary
In the past 10 years, more and more attention has been paid to the safety of drinking water supply. During the UV–chlorination process, THMs formed were higher than chlorine alone treatment, and the formation of HANs and HNMs increased[30,31]. We did found that TCNM formation increased by UV–chloramination compared by chlorination a lone[33] It has been reported UV–chloramination process formed the DBPs which are more cytotoxic than those by chloramination alone[34]. During the treatment of sewage or drinking water, primary and secondary amines can react with disinfectants to form carcinogenic and mutagenic nitrosamines, which brings potential health risk. There are few reports on the effect of amines in water on the formation of DCNM under UV/chlorine disinfection. The DCNM formation potential of three amine precursors and the variation of different forms of nitrogen in the reaction system was analysed
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