Comparison of Different Bacteria Inactivation by a Novel Continuous-Flow Ultrasound/Chlorination Water Treatment System in a Pilot Scale

Abstract

The existing traditional drinking water disinfection technology relies mainly on chlorine disinfection alone, which has high disinfection efficiency and can effectively inactivate most of the microorganisms in the water. However, it produces a series of harmful disinfection by-products (DBPs). Therefore, it is very necessary to study an efficient and environmentally friendly disinfection technology for drinking water. For this purpose, a novel continuous-flow ultrasound (US)/chlorination water treatment system was designed and developed. Escherichia coli (E. coli), Bacillus subtilis (B. subtilis), and Staphylococcus aureus (S. aureus) were selected as indicators of water treatment effects to (1) investigate the disinfection effects of different bacteria by US treatment alone at different single or dual frequencies; (2) explore the disinfection effects of US pretreatment with 8 mg/L NaClO on different bacteria to assess the promoting effects of US pretreatment; and (3) identify the optimum system process to satisfy the national standard for drinking water quality. Results showed that the dual-frequency US had better inactivation effects compared with single-frequency US, although it could not achieve an ideal disinfection level (complete disinfection). Further, 17 + 33 kHz dual-frequency US pretreatment had obvious enhancement of the disinfection efficiency, where 3.85 (E. coli), 3.65 (S. aureus), and 3.52 (B. subtilis) log reduction were achieved when 8 mg/L NaClO disinfection lasted 10 min, and finally all three bacteria achieved 4 log reduction after 30 min. Moreover, the treated water satisfied the Chinese national standard for drinking water quality, in which the residual chlorine concentration was below 4 mg/L. The utilization efficiency of disinfectant was improved approximately 40% by 17 + 33 kHz US pretreatment.

Ultrasound Technology Integration into Drinking Water Treatment Train

“…The common physical treatment methods include pulsed-electric field and plasma discharge [24,25], magnetic field [26], hydrodynamic cavitation [27], ultraviolet (UV) light [28], and ultrasound [29]. The combinations of physical-physical treatments such as UV light and ultrasound and physical-chemical treatments such as ultrasound and chlorine dioxide, ultrasound and ozone, and UV and ozone are also recommended [30].…”

Water purification using ultrasound waves: application and challenges

“…In the early to mid-1970s, numerous researchers explored the use of ultrasound as a disinfectant because of its ability to decrease bacterial sporal heat resistance (Burleson, Murray, & Pollard, 1975;Dahi, 1976). Ultrasound desinfection is now well documented to be related to cavitation phenomena (Zou & Tang, 2019). Many scientists studied the use of US water treatment techniques, alone or joined with other procedures for disinfection (Wu, 2017).…”

“…Extensive investigations were conducted on US disinfection techniques (Burzio et al, 2020;Doulah, 1977;Gogate, 2007;Zou & Tang, 2019). The energy generated during American irradiation in several combined mechanisms based on acoustic cavitations can inactive microorganism.…”

“…Use ultrasound with an ozone-powerful oxidant improves water and wastewater treatment through the production of emulsion from both suspended and dispersed particles, and through the prevention of ozone bubble coalescenzy, thus ensuring the total oxidation bubble area (Zou & Tang, 2019).…”

Çevre Mühendisliğinde Su Arıtımında Ultrases Uygulamaları

“…Klor kaynağı olarak ise NaClO kullanılmıştır. En fazla bakteri gideriminin 17+ 33 kHz frekansında gerçekleştiği tespit edilmiştir[34].…”