Enhanced Coagulation with Mn(III) Pre-Oxidation for Treatment of Micro-Polluted Raw Water

Abstract

Mn(III) oxidation technology has attracted increasing interest in recent years because of its fast decontamination kinetics and second-pollution-free characteristic. Whether it can be used as a pre-oxidation step to enhance conventional coagulation process remains to be evaluated. Herein, an Fe-coagulation/sedimentation process combined with Mn(III) pre-oxidation (Mn(III)+C/S), hypochlorite pre-oxidation (Cl2+C/S), and permanganate pre-oxidation (PM+C/S) was applied to treat simulated micro-polluted raw water. The removal performance of routine water quality indices (turbidity, dissolved organic carbon, total nitrogen, nitrate-nitrogen, ammonia-nitrogen, Pb(II), and Cr(VI)) and the emerging pollutants (acesulfame, carbamazepine, bisphenol S, and nano-ZnO) created by these three processes were researched. The mechanism of how Mn(III) pre-oxidation influences C/S was explored by identifying the transformation products of Mn(III), measuring the timely variation of flocs’ zeta potential and size, and scanning flocs’ micromorphology. Compared to Cl2+C/S and PM+C/S, Mn(III)+C/S exhibited its superiority in removing dissolved organic carbon (72.9%), total nitrogen (31.74%), and emerging pollutants (21.78%–93.49%). The enhanced removal of these contaminants by Mn(III)+C/S found its explanation in the strong oxidation power of Mn(III) and the multiple roles of in-situ formed MnO2 (e.g., flocculation core, adsorption co-precipitant, and densification agent). The acute toxicity tests confirmed that water treated by Mn(III)+C/S did not show a significant change in the associated toxicity. The findings of the present study indicate that Mn(III) oxidation technology shows great potential as an alternative to pre-oxidation technology of waterworks.

Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe

“…The optimum alum dosage (A o ) obtained from the procedure in the previous section was taken as the maximum dosage in experiments to determine the optimum combination of chlorine dioxide and alum. The rationale for this, is that the addition of a pre-oxidising agent should result in reduction of alum dosage since most organics and algae are expected to have been oxidised by the oxidant resulting in less alum required for coagulation (Yan et al 2019). Typical doses for pre-oxidation with chlorine dioxide range from 0.07 to 2 mg/L (Shams et al 2011).…”

Application progress of enhanced coagulation in water treatment

“…Chlorine dioxide pretreatment, like chlorine, has a positive effect on algae removal. 67 Lin 68 found that ClO 2 dosing had a strongest ability to lower algae viability and oxidize ionic and complexed soluble Mn. Shi 69 found that the optimal dose of 0.5 mg L À1 of Cl 2 could prevent the outbreak of Pseudomonas aeruginosa.…”

Emerging pollutants—Part II: Treatment

“…It is often reported that Mn 3+ oxidation technology is used as peroxidation step to strengthen the traditional coagulation process. Yan, Sun, et al (2019), Yan, Yuan, et al (2019) reported the treatment of simulated micro-polluted raw water by iron coagulation and sedimentation process combined with Mn 3+ peroxidation (Mn 3+ -C/S), hypochlorite peroxidation, and permanganate peroxidation. The target EPs includes acesulfame, carbamazepine, bisphenol S, and nano-ZnO.…”

“…In general, the chemical oxidation processes are used to degrade the EPs into the biodegradable intermediate. Then, further oxidation is carried out by biological method to improve the mineralization rate of EPs and the quality of effluent (Monteil et al, 2019; Wang, Ying, et al, 2019; Wang, Su, et al, 2019; Wang, Wang, et al, 2019; Wang, Huang, et al, 2019; Wang, Cai, et al, 2019; Wang, Zhu, et al, 2019; Wang, Yin, et al, 2019; Wang, Qian, et al, 2019; Wang, Zhang, et al, 2019; Yan, Sun, et al, 2019; Yan, Yuan, et al, 2019). The combination of various chemical oxidation methods can improve the production efficiency of active groups in the system, leading to the removal rate improvement of EPs (Chen, Zhu, et al, 2019; Chen, Zhang, et al, 2019; Figueredo, Rodríguez, Checa, & Beltran, 2019; Orimolade, Koiki, Peleyeju, & Arotiba, 2019; Sedlazeck et al, 2019; Wang, Ying, et al (2019); ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Wang, Su, et al (2019), Wang, Wang, et al (2019), Wang, Huang, et al (2019), Wang, Cai, et al (2019), Wang, Zhu, et al (2019), Wang, Yin, et al (2019), Wang, Qian, et al (2019), Wang, Zhang, et al (2019); Xu, Yang, et al, 2019; Xu, Zhao, et al, 2019).…”