10 years anniversary celebration in China: Constant Waterlevel Sequencing Batch Reactor (CWSBR)
CWSBR “Constant Waterlevel Sequencing Batch Reactor” is an innovative biological treatment technology for municipal wastewater. The application of the CWSBR technology started in 2000 in order to lower the costs of wastewater treatment plants significantly. After an intensive period of quality assurance by the patent holder “Gesellschaft für Abwasser- und Abfalltechnik mbH” (G.A.A) in Germany the international acceptance of CWSBR increased rapidly. In China the sole authorized technology holder and promotion representative, Dalian MEC Environmental Technology & Engineering Co., Ltd. (Dalian MECETC) realized the successful implementation of CWSBR in the market and achieved high social and economic benefits.
(01.06.2010) CWSBR is a low energy SBR process with an optimized biological activity which grants Class A of Integrated Wastewater Discharge Standard without the third stage treatment process. The structural shell is based on a constant water (CW) level pond system, which contains the low cost sequential batch reactor (SBR) process. As shown in picture 1, the main body is divided into three zones by two hydro sails. The zones represent the holding for wastewater influent, the SBR zone for wastewater treatment and the balancing zone respectively.
CWSBR accepts a continuous or imbalanced inflow due to variations of daily water utilization respectively. The SBR process works at regular cycles and independently from changes of the water volumes. These volumes may change continuously and are followed by a passive movement of the hydro sails. As a result, the water level of system is always constant.
The development of CWSBR was focused on the demand to reach Class A discharge standards under good economic conditions. Additionally the plant design had to be adaptable on the dynamic changes of urbanization in cities. Modern wastewater treatment has to support the implementation of new industrial locations in its surrounding and to balance even short term changes of wastewater composition.
In Europe such situation is given due to the rapid growth of electrification from biogas. If such technology will be established in front of older wastewater treatment plants the change of wastewater composition is able to disturb the microbiology of wastewater treatment intensive and sustainable. During the development of CWSBR these possibilities of dynamic wastewater quantities and qualities were already taken into account. In this context it has to be pointed out that CWSBR is the sole SBR technology which allows a dynamic change of water volume in the SBR zone under reliable maintenance of all technical equipment like blowers or pumps. This advantage results from the constant water level and allows a wide range of different water-sludge ratios according to the influent qualities. The result is, that CWSBR is able to deliver Class A discharge standards even if the ratios of organic and inorganic wastewater compounds do not fit the traditional values of urban wastewaters. Therefore CWSBR is a good choice for industrial locations with dynamic changes in wastewater quality as well for regions with an expectable increase of urban or industrial growth. Today different CWSBR frame sizes from 5.000 up to 50.000 tons/day are realized and they belong to the commissioners choice if a total treatment volume shall be established in one step or in accordance to the real growth of a region. CWSBR delivers this choice by its capability of a modular construction of the single pond systems, which can be arranged in parallel. Thus an enhancement of an CWSBR plant does not result in a complete new plant, it only demands another pond system.
Today, total treatment capacity of CWSBR process includes approx. 330.000 ton/day in the world. Especially in China an amount of 105.000 tons/day has been completed in four projects. Additionally, there are nine projects under construction in China, and it is estimated that the treatment amount will increase to 216.000 tons/day.
Dalian MECETC, a company with 20 years experience of waster water treatment, adopted the CWSBR technology in 2008 in close cooperation with G.A.A for the Chinese market. As a result a regionalized product was supplied at the beginning of 2009. With advanced production equipment, meaning material from Germany and processing technology from G.A.A, the quality of the regionalized product met the requirement of German quality completely. Meanwhile Dalian MECETC adapted characteristics of CWSBR to the demands of wastewater treatment in China.
The recent project (Wudalianchi WWTP of Heilongjiang Province in China) shows impressively why MECETC chose the CWSBR principle for China. The implementation of the modern SBR process in the shape of a pond system allows an operation even under extreme climatic conditions. The presented plant was commissioned on October 31, 2009 and major pollution indicators met the discharge limits steadily in the cold climate of –30 °Celsius.
No question that such extreme climatic conditions are critical for biological processes and it is necessary to safe the wastewater temperature from the influent over the whole water body. In comparison to conventional SBR plants, which are separated in three different over ground tanks, the pond system is much better isolated against extreme temperatures. Therefore the assembly of isolation material can be reduced on the short piping system between the single pond zones. This advantages result not only in a reliable wastewater treatment but also in the low cost structure of this technology. The total investment of plant is 29.00 million RMB Yuan and the treatment amount is 10.000 tons/day. The water quality of effluent complies with the Class A of Integrated Wastewater Discharge Standard.
With the rapid development of economy and the improvement of people’s living, the construction of sewage treatment devices has become one of the government’s most important methods to improve people’s life and to protect the environment by raising the water quality. Today’s sewage treatment requires an enhanced removal of nitrogen and phosphorus not only in new treatment plants but also in already established ones. CWSBR opens this way due to its ability of retrofitting in older plants without regulated biological activity. Following this aim the technology was developed in 2000 in Germany. However the utilization of CWSBR for large scale applications was initialized in China due to the international cooperation between G.A.A. and MECETC.
Authors: Zhan Ji Ling, Chief Engineer, Dalian MEC ETC Co., Ltd., Dalian 116001, China
Dr. Tim Koeckritz (CKO) and Axel Dederichs (CEO), G.A.A., Gesellschaft für Abwasser- und Abfalltechnik mbH, 23879 Mölln, Germany
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