UNITANK is a new wastewater treatment technology combining the advantages of Sequencing Batch Reactor, normal aeration tank and 3ditch oxidation treatment systems. It has been considered as an attractive pathway to be applied in small or middle wastewater treatment plants. It was chosen as the main process in Xingtai Wastewater Treatment Plant, Hebei Province, PR China. In this paper, the operation process, operation mechanism and features of UNITANK process were discussed in detail on the basis of the basic structure and the application in engineering.
Research on Operation Mechanism and Application in Engineering of UNITANK Process Dong-jie BAO 1, a,* , Jing LI 2,b and Peng ZHANG 3,c 1 Xingtai Polytechnic College, Xingtai, Hebei, 054035, China 2 Xingtai Polytechnic College, Xingtai, Hebei, 054035, China 3 Xingtai Polytechnic College, Xingtai, Hebei, 054035, China a bdjer330@163.com, b 1391369317@qq.com, c zhangpeng-jx@163.com *Corresponding author Keywords: UNITANK Process, Operation Mechanism, Wastewater Treatment. Abstract. UNITANK is a new wastewater treatment technology combining the advantages of Sequencing Batch Reactor, normal aeration tank and 3-ditch oxidation treatment systems. It has been considered as an attractive pathway to be applied in small or middle wastewater treatment plants. It was chosen as the main process in Xingtai Wastewater Treatment Plant, Hebei Province, PR China. In this paper, the operation process, operation mechanism and features of UNITANK process were discussed in detail on the basis of the basic structure and the application in engineering. Basic Structure of UNITANK Reactor UNITANK process, named the alternating biological treatment technology, is also called the single pool system. It is the patent technology of Seghers Engineering Water NV in the late 80’s. There are three lattices (also known as tank A, B and C) in one pool. The tanks share the public wall and hydraulic connect with each other through the public channel at the bottom. Outlets of the public channel belonging to the side tanks are located in the center of the tanks. Stabilizing covers are set above the outlets to prevent the disturbance of the sludge. There is a set aeration system in each tank. The fixed effluent weirs and sludge slots are arranged in the outside two tanks (A, C tank) .Tanks A and C are used as the aeration tank and the settling tank alternately, while tank B is only used as a aeration tank [1-3]. It is a continuous influent and alternate working system, which is shown in Fig.1 Engineering Application in Xingtai Wastewater Treatment Plant Overview of the Project In the secondary project of Xingtai Wastewater Treatment Plant，the capacity of UNITANK process is 10xl0 4 m 3 /d. The quality of influent and the designed quality of effluent is shown in Table 1. The designed quality of effluent achieves the secondary standard of "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant" (GB18918-2002,China). Table 1. The Quality of Influent and the Designed Quality of Effluent items BOD 5 COD SS T-N NH 3 -N T-P influent [mg/L] 123~229 267~376 105~245 33~52 22~41 1.91~3.99 average influent[mg/L] 186 326 201 46 33 3.3 effluent [mg/L] ≤30 ≤100 ≤30 ≤30 ≤25 ≤3.0 Advanced Materials Research Vol. 937 (2014) pp 370-374 Online available since 2014/May/07 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.937.370 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 130.159.18.180, University of Strathclyde, Glasgow, United Kingdom-06/10/14,05:21:40) Technical Process The technical Process is shown in Fig.2. The layout of the tanks is shown in Fig.3. Parameters of the Project There are four groups of UNITANK reactor, each group contains three rectangular tanks marked A, B and C. Parameters of the project is shown in Table 2. Fig. 1. Basic Structure of UNITANK Reactor Fig. 2. The Technical Process of the Secondary Project Advanced Materials Research Vol. 937 371 Fig. 3. The Layout of the Tanks Table 2. The Parameters of the Project Tank A Tank B Tank C size [m] 32x32x5 (depth) 32x15x5 (depth) 32x32x5 (depth) effective depth [m] 4 4 4 treatment capacity [m 3 /d] 2.5xl0 4 volumetric load [kg BOD/ (m 3 ·d)] 0.33 sludge load [kgBOD/(kgMLVSS·d)] 0.104 surface load [m 3 /(m 2 ·h)] 1.02 weir load [L/(s·m)] 1.55 sludge concentration [kg/m 3 ] 4 aerobic sludge age [d] 9 hydraulic retention time [h] 9.7 Operation Mechanism and Features Operation Cycle and Timing of the Reactor The alternating biological reactor operates according to the period of cycle. Each cycle comprises two main operation stages and two transition stages [4-6]. The two main operation stages are mutually symmetrical and connected through the transition stage. The operation cycle and timing of the reactor in Xingtai Wastewater Treatment Plant is shown in Table 3. There are 12 hours in per cycle including 2×4 hours of the main stages and 2×2 hours of the transition stages. Table 3. Operation Cycle and Timing of the Reactor stages time [h] tank A tank B tank C main stage 1 stage 1 4.0 influent, aeration aeration settling, effluent stage 2 0.5 aeration influent, aeration settling, effluent stage 3 1.5 settling influent, aeration settling, effluent main stage 2 stage 4 4.0 settling, effluent aeration influent, aeration stage 5 0.5 settling, effluent influent, aeration aeration stage 6 1.5 settling, effluent influent, aeration settling 372 Material Science and Environmental Engineering Operation Mechanism and Feature The Operation mechanism is shown in Fig.4. In Fig.4, the stages and the state of each tank are displayed in detail. The System Has Characteristics of High Efficiency The system is more suitable for treating wastewater with high concentration than the general activated sludge methods. The sewage flowing into the side tank will be better handled because there is a great quantity of activated sludge with high concentration in the tank [7]. This is due to the operation as a sedimentation pool in the last stage of the cycle. With continuous flowing, concentration of pollutant in liquid phase increases while the absorption and oxidation capacity of activated sludge is also constantly strengthened. Pollutant is adsorbed and degraded in a relatively short time. The System Has a Certain Removal Function of Nitrogen and Phosphorus The system would have nitrogen and phosphorus removal function by setting the non aeration stage during the aeration period in order to form the alternate states of anaerobic, anoxic and aerobic and by controlling the technical conditions such as the flow, time and cycle. The System Has the Advantages of Compact Structure, Less Land Occupation and Cost-efficient The structure of UNITANK process is compact because the tanks connect with each other through the public wall. The influent flows through the punches which reduces the head loss. Compared with the common activated sludge process, it does not need another secondary sedimentation tank and facilities for sludge returning. The system has the advantages of less land occupation, cost-efficient, reliable operation and convenient maintenance because of fewer types of equipment. Fig. 4. The Operation Mechanism Advanced Materials Research Vol. 937 373 Conclusion UNITANK is an effective technology for wastewater treatment with the advantages of high efficiency, certain removal function of Nitrogen and Phosphorus, compact structure, less land occupation, cost-efficient, reliable operation and convenient maintenance. It has been considered as an attractive pathway to be applied in small or middle wastewater treatment plants. Acknowledgements This work was financially supported by Science and Technology Support Program of Hebei Province (13273605), the Higher School Science and Technology Foundation of Hebei Province (QN20131178), Xingtai Science and Technology Support Program (2013ZC234). References [1]Henze M, Grady C P L, Gujer Jr et al., in: IAWPRC Scientific and Technical Report No.3,London, UK,1987. [2]Henze M, Gujer W, Mino T et al., in: Water Sci Technol, Issue1,Vol.39 (1999), p. 165-182. [3]Vriens L et al., in: Water,1990, p.52. [4]Dongjie Bao, Zhanmeng Liu and Jing Li, in: Applied Mechanics and Materials, Vols.361-363 (2013), p. 640-643. [5]V. N. Samokhin: Design Handbook of Wastewater Systems (Allerton Press, Inc., New York 1997). [6]Jeffrey A. Nathanso: Basic Environmental Technology: Water Supply, Waste management, and Pollution Control (Pearson Education., publishing as Prentice Hall 2003). [7]Fagen Zhang, Junxin Liu, in: Journal of Environmental Sciences, Issue2, Vol.19 (2007), p. 142. 374 Material Science and Environmental Engineering Material Science and Environmental Engineering 10.4028/www.scientific.net/AMR.937 Research on Operation Mechanism and Application in Engineering of UNITANK Process 10.4028/www.scientific.net/AMR.937.370 DOI References [2] Henze M, Gujer W, Mino T et al., in: Water Sci Technol, Issue1, Vol. 39 (1999), pp.165-182. http://dx.doi.org/10.1016/S0273-1223(98)00829-4 . Science and Environmental Engineering Material Science and Environmental Engineering 10.4028/www.scientific.net/AMR.937 Research on Operation Mechanism and Application in Engineering of UNITANK. Research on Operation Mechanism and Application in Engineering of UNITANK Process Dong-jie BAO 1, a,* , Jing LI 2,b and Peng ZHANG 3,c 1 Xingtai Polytechnic College, Xingtai,. 0.5 settling, effluent influent, aeration aeration stage 6 1.5 settling, effluent influent, aeration settling 372 Material Science and Environmental Engineering Operation Mechanism and Feature