Testing combined application of ultraviolet and ultrasonic disinfection of wastewater

Chia sẻ: Nguyễn Thảo | Ngày: | Loại File: PDF | Số trang:8

Thêm vào BST

Báo xấu

15
lượt xem 1
download

Download Vui lòng tải xuống để xem tài liệu đầy đủ

This article discusses testing results of industrial trial of new wastewater disinfection comprised of combined use of ultrasonic and ultraviolet methods at final stage of wastewater treatment aimed at elimination of pathogenic organisms, thereby preventing spread of infectious diseases.

Chủ đề:

Bình luận(0) Đăng nhập để gửi bình luận!

Lưu

Nội dung Text: Testing combined application of ultraviolet and ultrasonic disinfection of wastewater

International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 03, March 2019, pp. 1566-1573. Article ID: IJMET_10_03_157 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication Scopus Indexed TESTING COMBINED APPLICATION OF ULTRAVIOLET AND ULTRASONIC DISINFECTION OF WASTEWATER Nikolay Lebedev Alexandra-Plus, Vologda, Russian Federation Vladimir Grachev Scientific Research Institute for Environmental Issues, Moscow, Russian Federation Global Ecology Center, Faculty of Global Studies, Lomonosov Moscow State University, Moscow, Russian Federation Olga Pliamina Scientific Research Institute for Environmental Issues, Moscow, Russian Federation Oleg Lebedev, Dina Lukichyova OOO Novotech-ECO, Vologda, Russian Federation Valeriy Doilnitsyn, Andrey Akatov Peter the Great St.Petersburg Polytechnic University, St. Petersburg, Russian Federation Leonid Leonov SUE “Vodokanal of St. Petersburg”, St. Petersburg, Russian Federation ABSTRACT This article discusses testing results of industrial trial of new wastewater disinfection comprised of combined use of ultrasonic and ultraviolet methods at final stage of wastewater treatment aimed at elimination of pathogenic organisms, thereby preventing spread of infectious diseases. The new method has been developed, patented and tested at one of the leading water service companies: SUE “Vodokanal of St. Petersburg”. The integrated assembly was fabricated at Novotech-ECO and installed at South-West Wastewater Treatment Plant (SWWTP, SUE “Vodokanal of St. Petersburg”). The test results demonstrated efficiency of combined ultraviolet and ultrasonic treatment of wastewater both in terms of disinfection improvement and in terms of the assembly operation stability through prevention of biological films deposition on lamp sleeves. The latter fact served as background of the challenging project on improvement of existing system of ultraviolet disinfection at SWWTP. http://www.iaeme.com/IJMET/index.asp 1566 editor@iaeme.com
Testing Combined Application of Ultraviolet and Ultrasonic Disinfection of Wastewater Key words: Combined disinfection methods, pathogenic microorganisms, ultrasonic and ultraviolet disinfection, wastewater, water treatment. Cite this Article Nikolay Lebedev, Vladimir Grachev, Olga Pliamina, Oleg Lebedev, Dina Lukichyova, Valeriy Doilnitsyn, Andrey Akatov and Leonid Leonov, Testing Combined Application of Ultraviolet and Ultrasonic Disinfection of Wastewater, International Journal of Mechanical Engineering and Technology, 10(3), 2019, pp. 1566-1573. http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=3 1. INTRODUCTION Municipal wastewater usually contains significant amount of pathogenic microorganisms, including infectious agents. Their elimination prior to discharge is an important final treatment stage preventing propagation of infectious diseases. This issue is solved by means of chlorination and ozonation, wastewater ultraviolet (UV) treatment which doesn’t generate toxic substance and which disinfection efficiency is higher in comparison with treatment by chemical agents. Sometimes exposure to UV radiation is combined with addition of reagents [1]. Mercury-vapor lamps are widely applied in practice [2]. It should be mentioned that the UV disinfection efficiency decreases in case of high color index and turbidity of medium typical of wastewater. In addition, it is noted that in the last 15- 20 years resistance of pathogenic microflora against ultraviolet increased four-fold [3]. One more negative factor decreasing efficiency of this procedure is salt deposition and biological fouling of sleeves of UV lamps [4]. As a consequence, the sleeve surfaces should be regularly cleaned. After development of powerful ultrasonic radiators the researchers began to consider the possibility of their stand-alone application for disinfection treatment. Specified effects occurring under the action of ultrasound in liquid mediums, namely: high-speed micro-streams > 1 km/s, intensive impact waves > 1 GPa, local heating areas > 1000 K, free radicals resulting from cavitation bubble collapse, can obviously promote destruction of pathogenic flora [5]. However, it was experimentally demonstrated that upon short impact time or low radiating power the amount of microorganisms in some cases can even increase [6,7]. Thus, ultrasonic treatment is applied only in combination with chemical reagents or, for instance, with UV water treatment [2]. Combined ultrasonic and UV water treatment was proposed by Lebedev and coauthors in 2016, it is considered the most promising disinfection procedure due to combination of positive features of both approaches [8]. It is confirmed that this combination provides synergetic increase in disinfection efficiency due to the following effects of ultrasonic treatment: 1) crushing of suspended particles inside which microorganisms can exist [9], as well as crushing of microorganism clusters [10] and destruction of their cell structure [11,12] with subsequent availability and respectively increased sensitivity of microorganisms to ultraviolet (from this point of view ultrasonic treatment should precede UV radiation); 2) intensive water agitation promoting transport of distant layers to the lamp sleeves, thus providing uniform treatment of feed water; 3) prevention of biological fouling or salt deposition on lamp sleeves [3,13], thus providing retention of initial intensity of lamp radiation during overall lifetime. As a consequence of combined application of UV and ultrasonic treatment not only disinfection efficiency increases, but lamp lifetime also increases, frequent pauses for sleeve cleaning are eliminated [13], the application of acid solutions aimed at cleaning and etching of http://www.iaeme.com/IJMET/index.asp 1567 editor@iaeme.com
Nikolay Lebedev, Vladimir Grachev, Olga Pliamina, Oleg Lebedev, Dina Lukichyova, Valeriy Doilnitsyn, Andrey Akatov and Leonid Leonov quartz sleeves is not required, which decreases maintenance costs and promotes environmental safety. In some studies it is stated that the combined wastewater disinfection is more cost efficient [2,3,6,13]. In recent years the combined procedure has been tested several times proving its high efficiency [2,3,13-16]. Moreover, Novotech-ECO (Vologda, Russia) and SVAROG (Moscow) manufacture assemblies for combined UV and ultrasonic water disinfection. The technology developed by Novotech-ECO on the basis of piezoceramic radiators is the most promising at present. The number of assemblies delivered from 2006 on the basis of this method is more than three hundred. Such assemblies are successfully applied both in Russia and in neighboring countries. 2. MATERIALS AND METHODS The UOV-SV-5 assembly (Figure 1), designed and manufactured by Novotech-ECO (Russian Federation), applies the aforementioned approach. It is comprised of pre-cavitator connected with disinfection chamber and provides wastewater treatment at the flow rate up to 5 m3/h. Figure 1 UOV-SV-5 assembly at testing site The UOV-SV-5 was tested at SWWTP (SUE “Vodokanal of St. Petersburg”, Russian Federation) from October 2015 to December 2016. The assembly was installed at the station of UV treatment, where wastewater was supplied after preliminary mechanical and complete biological cleaning. According to chemical analysis the content of suspended substances in this water was in the range of 6.7-17 mg/dm3, and chemical consumption of oxygen was 24-61 mg/dm3. (It should be mentioned that after water treatment using this assembly these figures remained nearly the same). Water prior to UV treatment was taken from trough by pump, then conveyed through the assembly and discharged back to the channel. Bacteriological analysis of water sampled at the assembly input and output was performed in Water Research and Control Center (St. Petersburg, Russian Federation). The following indicators were controlled: Coliphage, Total coliforms, E. coli, Enterococcus, Staphylococcus. The tests were comprised of three stages. The first stage (I) was devoted to various disinfection variants at low flow rate of wastewater via the assembly (0.5-0.7 m3/h), herewith, http://www.iaeme.com/IJMET/index.asp 1568 editor@iaeme.com
Testing Combined Application of Ultraviolet and Ultrasonic Disinfection of Wastewater the UV lamp sleeves were clean upon sampling, without traces of salt deposition or biological fouling. The second stage (II) was characterized by increased water flow rate (8-10 m3/h). And finally, the third stage (III) implied study of intensity of biological fouling and salt deposition on UV lamp sleeves during long-time operation of assembly at low wastewater flow rate (0.5- 0.7 m3/h). The details of the stages are summarized in Table 1. Table 1 Operation modes of UOV-SV-5 assembly at various testing stages Stage Mode Description I II III All ultrasonic radiators are active (8 units) (both in pre- US + cavitator and in disinfecting chamber) US-k Ultrasonic radiators are active only in pre-cavitator (4 units) + UV lamps and ultrasonic radiators are active only in US+UV-1 + disinfection chamber (4 units) US+UV-2 UV lamps and all ultrasonic radiators are active (8 units) + + + Only UV lamps are active, all ultrasonic radiators are UV-k + + + deactivated 3. RESULTS AND DICUSSION The results of the first testing stage are summarized in Table 2, where either logarithmic coefficients of inactivation (LCI) are shown, or complete treatment for the indicator is indicated. The LCI is calculated as decimal logarithm of the ratio of living cells content in a unit of wastewater volume before and after its treatment. Table 2 Results of the first testing stage (flow rate: 0.5-0.7 m3/h) LCI or result of operation in mode Indicator Initial range US US-k US+UV-1 US+UV-2 UV-k 400-1000 Coliphage 0 0 Complete treatment BFU/100 cm3 32000-62000 Total coliforms 0 0 1.85 2.78 2.34 CFU/100 cm3 29000-42000 E. coli 0 0.23 2.18 4.51 4.62 CFU/100 cm3 15000-32000 Enterococcus 0 0.32 Complete treatment CFU/100 cm3 45-150 Staphylococcus 1.65 0 Complete treatment CFU/100 cm3 It is obvious that ultrasonic treatment alone does not provide significant disinfection. Weak intensification of UV disinfection by ultrasound was observed, where the most significant contribution was made by pre-cavitator, whereas ultrasonic radiators in disinfection chamber exerted even negative effect. Probably, crushing of suspended particles and microorganism clusters with subsequent removing of their protection against UV radiation was the dominating mechanism. In addition, low wastewater flow rate via the assembly predetermined high efficiency of UV disinfection and minor contribution of ultrasonic treatment. Thus, at the second stage it was decided to reject purely ultrasonic modes (US, US-k), as well as the mode without pre-cavitator (UV+US-1), and to increase water flow rate via the assembly. The results are summarized in Table 3 and in Figure 2. http://www.iaeme.com/IJMET/index.asp 1569 editor@iaeme.com
Nikolay Lebedev, Vladimir Grachev, Olga Pliamina, Oleg Lebedev, Dina Lukichyova, Valeriy Doilnitsyn, Andrey Akatov and Leonid Leonov Table 3 Results of the second testing stage (flow rate: 8-10 m3/h) LCI or result of operation in mode Indicator Initial range US+UV-2 UV-k 330-1200 Coliphage Complete treatment (> 3.08) 2.07 BFU/100 cm3 30000-83000 Total coliforms 2.25 2.75 CFU/100 cm3 29000-49000 E. coli 3.57 3.20 CFU/100 cm3 4700-25000 Enterococcus 4.03 3.06 CFU/100 cm3 140-270 Staphylococcus Complete treatment (>2.14) 2.09 CFU/100 cm3 Figure 2 Results of the second testing stage (flow rate: 8-10 m3/h) Ultrasonic treatment of wastewater flow via the assembly obviously increases (by several times in terms of absolute values) disinfecting effect of UV radiation actually in terms of all considered properties, whereas ultrasound itself at the first stage did not demonstrate disinfecting action. At the third stage the capability of ultrasound to prevent biological fouling and salt deposition on UV lamp sleeves was studied. The flow rate was again decreased to 0.5-0.7 m3/h, but samples were taken after long-term continuous operation (at least one month). Thus, the assembly operation stability was tested. The flow rate was reduced to maintain the experimental integrity and to exclude possibility of discharge of depositions and impurities on the lamp sleeves as a consequence of high linear flow rate. The results are summarized in Table 4 and in Figure 3. Table 4 Results of the third testing stage (flow rate: 0.5-0.7 m3/h) http://www.iaeme.com/IJMET/index.asp 1570 editor@iaeme.com
Testing Combined Application of Ultraviolet and Ultrasonic Disinfection of Wastewater LCI or result of operation in mode Indicator Initial range US+UV-2 UV-k 580-970 Coliphage Complete treatment (>2.99) Complete treatment (>2.76) BFU/100 cm3 110000-190000 Total coliforms 4.11 3.70 CFU/100 cm3 49000-72000 E. coli 4.90 3.70 CFU/100 cm3 22000-56000 Enterococcus 4.20 3.90 CFU/100 cm3 45-270 Staphylococcus Complete treatment (>2.43) Complete treatment (>1.65) CFU/100 cm3 Figure 3 Results of the third testing stage (flow rate: 0.5-0.7 m3/h, long-term continuous operation in corresponding mode) The advantages of ultrasonic intensification were confirmed at the third testing stage: the disinfection efficiency in terms of all considered microorganisms increased by several times (in absolute values). In addition, surfaces of UV lamp sleeves were visually inspected after long-time operation in each mode, and intensity of deposits was studied by gravimetric method. The second indicator was measured as follows: the deposits were removed from the sleeves by wiping their surfaces using polyester rayon fabric. The wiping was performed after predetermined time of the assembly operation in respective mode. The rate of biological fouling and salt deposition was estimated by weight difference of air dry fabric before and after wiping of UV lamp quartz sleeves. This difference is proportional to total weight of deposited impurities and products of biological fouling of the assembly during operation. Total weight of air dry deposits on three sleeves with respect to 1 m3 of conveyed wastewater in UV+US-2 mode (operation of all three UV lamps and eight ultrasonic radiators) was 45 µg/m3, and in UV-k mode (operation of only three UV lamps) – 300 µg/m3. Therefore, http://www.iaeme.com/IJMET/index.asp 1571 editor@iaeme.com
Nikolay Lebedev, Vladimir Grachev, Olga Pliamina, Oleg Lebedev, Dina Lukichyova, Valeriy Doilnitsyn, Andrey Akatov and Leonid Leonov ultrasonic treatment made it possible to decrease the intensity of biological fouling and salt deposition by 6.7 times. 4. CONCLUSION The test results proved the efficiency of combined UV and ultrasonic treatment of wastewater both in terms of improved disinfection and in terms of assembly operation stability by prevention of deposition of biological films and salts on lamp sleeves. The latter fact initiated advanced project of improvement of existing system of UV disinfection of waste water at SWWTP. This implementation by the leading company would permit to recommend the combined disinfection approach for wide scale application [17-19]. REFERENCES [1] Degremont, G. Water Treatment Handbook, Vol. 2, 6th edition. Newtown, UK: Intercept Ltd, 1991. [2] Sokolova, N. F. Means and methods of water disinfection. Review. Medical Alphabet, 1(5), 2013, pp. 44-54. [3] Ulyanov. A. N. Lazur technology – a new step in water supply and sewage decontamination. Water: Chemistry and Ecology, 3, 2009, pp. 11-15. [4] Sevryukov, I. and Afanaseva, E. Some aspects of the security of the population in emergency situations with the pollution of the hydrosphere. Civil Security Technology, 10(1/35), 2013, pp. 22-25. [5] Osman, Н., Lim, F., Lucas, M. and Balasubramaniam, P. Development of an ultrasonic resonator for ballast water disinfection. Physics Procedia, 87, 2016, pp. 99-104. DOI: 10.1016/j.phpro.2016.12.016. [6] Akhmedova, O. O., Stepanov, S. F., Soshinov, A. G. and Bakhtyarov, K. N. Efficiency improvement of local water treatment stations by means of integrated electrophysical procedures. Sovremennye Problemy Nauki i Obrazovaniya, 5, 2009, pp. 56-60. [7] Sesal, N. C. and Kekeç Ö. Effects of pulsed ultrasonic on Escherichia coli and Staphylococcus aureus. Transactions of the Royal Society of tropical medicine and hygiene, 108(6), 2014, pp. 348-353. DOI: 10.1093/trstmh/tru052. [8] Lebedev, N. M., Lebedev, O. Yu., Grachev, V. A., Pankova, G. A., Rublevskaya, O. N., Vasiliev, A. P. and Doilnitsyn. Device for water disinfection in the stream. Patent RU 2664920 C2. Date of filing: 05.02.2016. Date of publication: 23.08.2018 Bulletin No. 24, 2017. [9] Cui, X. F., Talley, J. W., Liu, G. J. and Larson, S. L. Effects of primary sludge particulate (PSP) entrapment on ultrasonic (20 kHz) disinfection of Escherichia coli. Water Research, 45(11), 2011, pp. 3300-3308. DOI: 10.1016/j.watres.2011.03.034. [10] Jin, X., Li, Z. F., Li, Y. L. and Xu, C. Improved wastewater ultraviolet disinfection by ultrasonic pre-treatment. Proceedings of 2009 Beijing International environmental technology conference, Beiging, PRC, 2009, pp. 498-505. [11] Zhang, S. and Wu, C. Effect of Wastewater Ultraviolet Disinfection of Power Ultrasonic Enhancement. 3rd International Conference on Bioinformatics and Biomedical Engineering, 1(11), 2009, pp. 4890-4895. DOI: 10.1109/ICBBE.2009.5162720. [12] Bolotova, Yu. V. and Karelina, K. A. Legionella bacteria in water supply system. Pathogenic organisms control. Bulletin of Perm National Polytechnic University, 3(19), 2015, pp. 43-59. [13] Lebedev, N. M., Kazukov, O. V., Vasiliev, A. P. and Pronin, G. K. Combined ultrasonic and ultraviolet water treatment facilities for disinfection of drinking water, water of pool and wastes: experience of application. Proceedings of the 8th Interregional conference: http://www.iaeme.com/IJMET/index.asp 1572 editor@iaeme.com
Testing Combined Application of Ultraviolet and Ultrasonic Disinfection of Wastewater Geology, resources and issues of Bashkortostan, Ural and adjacent regions, Ufa, Russia, 2010, pp. 275-276. [14] Lyamtsov, A. K., Kuz`michev, A. V., Tikhomirov, D. A. and Lamonov, N. G. Water treatment facility at cattle farms by ultrasonic cavitation and ultraviolet radiation. Innovatsii v selskom khozyaistve, 3(13), 2015, pp. 90-93. [15] Sosnin, E. A., Leepatov, E. I., Skakun, V. S., Panarin, V. A., Tarasenko, V. F., Zhdanova, O. S. and Goltsova, P. A. Ultraviolet radiation and ultrasonic oscillations impact on wastewater. Sovremennie nauchnie issledovania i innovatsii, 3(59), 2016, pp. 125-131. [16] Torres-Palma, R. A., Gibson, J., Droppo, I. G., Seto, P. and Farnood, R. Surfactant-assisted sono-breakage of wastewater particles for improved UV disinfection. Water, Air and Soil Pollution, 228(3), 2017, pp. 106. [17] Karmazinov, F., Onishchenko, G., Grachev, V., Rakhmanin, Yu. and Nefedova, E. Drinking water quality benchmarking. St. Petersburg: Novyi Zhurnal, 2010. [18] Karmazinov, F., Onishchenko, G., Grachev, V., Rakhmanin, Yu., Kirillov, V., Rublevskaya, O., Kirillov, D., Volkova, I., Plyamina, O., Zholdakova, Z. and Sinitsyna, O. Channelization system benchmarking, Vol. 1. St. Petersburg: Novyi Zhurnal, 2011. [19] Karmazinov, F., Onishchenko, G., Grachev, V., Rakhmanin, Yu., Kirillov, V., Rublevskaya, O., Kirillov, D., Volkova, I., Plyamina, O., Zholdakova, Z. and Sinitsyna, O. Channelization system benchmarking, Vol. 2. St. Petersburg: Novyi Zhurnal, 2012. http://www.iaeme.com/IJMET/index.asp 1573 editor@iaeme.com