Comparison of disinfectants for drinking water: chlorine gas vs. on-site generated chlorine

Abstract

The feasibility of on-site generated chlorine (OSG chlorine) as an alternative disinfectant to chlorine gas was evaluated in terms of total organic carbon (TOC) removal, disinfection efficiency, biofilm control, disinfection by-products (DBPs) formation, chlorine decay rate, and volatility. Chlorine gas decreased the pH of the treated water by -0.1 per mg/L of free available chlorine (FAC) while OSG chlorine increased the pH by + 0.06 per mg/L. OSG chlorine with more hypochlorite ion (OCl-) at higher pH was less effective in the inactivation of suspended bacteria and TOC removal but remained in the distribution system longer and controlled biofilm formation more effectively than chlorine gas. The DBPs formation by OSG chlorine was not significantly different from that by chlorine gas except for the reduction of Haloacetonitriles. Hypochlorous acid (HOCl) was more volatile than OCl-, indicating the lower volatility of FAC in the OSG chlorine-treated water. Two types of OSG systems, “Mixed oxidants” and OSG hypochlorite, did not show any significant difference in disinfection, DBPs formation, and chlorine decay rate (paired t-test, p = 0.40, 0.11 ~ 0.70, > 0.42). A significant synergy effect by oxidants other than FAC cannot be expected in the use of “mixed oxidants” at a water treatment plant.

Kinetic Models of Disinfection with Sodium Hypochlorite and Peracetic Acid of Bacteria Isolated from the Effluent of a WWTP

“…For example, with the B. subtilis (ATCC 6633) strain, an inactivation of 3 log was achieved, with a C•t of 127 mg•min/L (pH 5.6, initial chlorine of 2 mg/L) [65]. Reductions of 1-2 log with C•t values of 467-671 mg•min/L (gas chlorine: 0.5-1 mg/L, pH 7.2) have been reported with the same strain [66]. C•t values of 103-386 mg•min/L were reported to inactivate 2 log at pH 5.6-8.2 [67].…”

“…The disinfection of K. pneumoniae with 15 mg/L of NaClO showed a concave curve, which is properly described by the Weibull model, while the B. subtilis inactivation with 15 and 30 mg/L of the same disinfectant was adequately described by the Weibull and Geeraerd models, respectively. The chlorine inactivation of endospores of B. subtilis certified strains has been described using the Chick-Watson delay model [30,[65][66][67]72]. In those assays, doses lower than 10 mg/L of Cl2 were used, and the model was obtained by a graph of IU (log N/N0) vs. C•t, which describes a shoulder effect followed by a linear trend, which is different from what is presented in this study (Figures 3 and 4).…”

Kajian Penyisihan Amonia dalam Pengolahan Air Minum Konvensional

“…Klorin pada umumnya berupa gas klorin (Cl 2 ) atau larutan natrium hipoklorit (NaOCl) [36]. Gas klorin lebih banyak digunakan karena unggul dalam aspek biaya dan keandalannya, tetapi penanganannya relatif sulit dan butuh keahlian & fasilitas tertentu [37].…”

A Reflection on Sustainable Anode Materials for Electrochemical Chloride Oxidation

“…"On-site" chlorine production and immediate utilization through the direct electrolysis of a specific aqueous system enables efficient water treatment and overcomes the risk of chlorine storage and transport. [15,18] The direct electrochemical oxidation of chloride ions in water produces HOCl and hypochlorite, usually termed "free chlorine" or "active chlorine" (AC). Most electrochlorination (EC) processes use a simple undivided cell without a separator.…”