At 8:30 a.m. November 4, 2017, Saturday, the students of the Department of Civil Engineering, International Campus, Zhejiang University assembled on the bus in front of the Residential College for a half-day trip to a waterworks. Some might wonder, “What is worth seeing at a waterworks?” Initially, many of us had the same question. However, the result of this trip was far beyond our imagination.
After getting off the bus, we were warmly received by the Manager of Guanjinggang Waterworks, who could hardly wait to brief us on the waterworks. We came to know from his words that there are two waterworks with deep treatment and purification processes in Jiaxing, with a daily water supply capacity of up to 550,000 tons. Guanjinggang Waterworks is one of them. It won the honor “Modern Waterworks for Urban Water Supply in Zhejiang Province” in 2009, and was selected as a national “Project for Drinking Water Guarantee Integration Technology and Comprehensive Demonstration in the Lower Reaches of the Yangtze River”. We also learnedfrom the Ministry of Housing and Urban-Rural Development that the “Jiaxing Model” has become a role model in China for water resource management. It is indeed difficult to identify another waterworks in China,which is comparable to Guanjinggang Waterworks in both technology and management.
Why is a national role model of waterworks located in Jiaxing, a city much less known than other cities in Zhejiang, such as Hangzhou, Ningbo, and Wenzhou? In fact, the water in Jiaxing ismuch inferior to that in the Qiandao Lake region in terms of quality, and is slightly-polluted water of Category IV or V. The major water source is the Guanjinggang Canal, which runs through the local wetland. Due to the scarcity of water resources and the increasingly severe environmental problems, the people in Jiaxing carried out in-depth research into water purification and management. They introduced the state-of-the-art technologies and purchased equipment from other countries, and then adapted them to the local context. Eventually, through their hard work, the water in Jiaxing, after deep treatment and purification, has reached the WHO standard.
After the briefing, we began with the visit. The Manager showed us every step of the water treatment procedures at the waterworks. The high-end industrial equipment and the Manager’s vivid description made the visit very fruitful for us. In Jiaxing, other waterworks employ the composite process of bio-pretreatment—enhanced treatment—ozone—biological and activated carbon filtration pool. However, Guanjinggang Waterworks has courageously made innovations by introducing the new composite process of ozone catalysis and oxidation—upward flow biological activated carbon—post-positioned micro-flocculation enhanced sand filtration, thus effectively reducing the leakage risk of disinfection by-products and microorganisms.
Our first stop wasthe suspended carrier biological contact oxidation pool of the bio-pretreatment process. What came into view was the large number of small black balls floating in the pool, which were filled with suspended carriers. On one side of the pool, a water pipe was pumping compressed air into the pool. Thus, the suspended carrier was in the fluid state during aeration. This not only increases the oxygen utilization rate and mass transfer efficiency, but is also conducive to evenly distributing water and air, enhances reaction efficiency, and reduces the retention time as the carrier separates air and water. In addition, the waterworks also applies additional grid design in the surrounding area, achieving higher efficiency, but has the defect of breeding green algae, which requires regular cleaning. The waterworks combines the two methods, with the attitude of seeking truth from facts and maintaining flexibility at the same time.
The next stop was the intermediate high-density sedimentation tank in the enhanced traditional process. This process is a unique feature of Guanjinggang Waterworks. The equipment was imported from abroad, and the localization was done by the waterworks. The small area of this pool and the short flocculation sedimentation time reduce the consumption of alum. What is more important is that there may be no need for concentration pool. At the bottom of the sedimentation tank, sludge is concentrated and scraped. The sludge is automatically removed, dramatically saving the relevant costs.
In addition to the intermediate high-density sedimentation tank, in its second-phase project, Guanjinggang Waterworks also employs the traditional horizontal sedimentation tank. Although it covers a large area, it does not require people’s supervision. The mixed use of these two types of tanks helps to guarantee the water supply in Jiaxing.
Regarding the deep treatment process, the core is the ozone—biological and activated carbon process, which can efficiently remove the soluble small molecule organics. This effectively promotes the oxidation and degradation of the organic substances in the water, further reducing the residue ozone in the oxidation water, increasing oxygen dissolved in the effluent. As a result, aerobic microorganisms form a biomembrane of microbes on the top of the activated carbon particles, significantly enhancing the ability of the activated carbon bed and prolonging the lifespan of activated carbon.
Due to the time limit, we left the waterworks, all yearning for more. Guanjinggang Waterworks may be considered as an epitome of China’s infrastructure construction. It flexibly combines the traditional methods and automation and IT technologies. The flexible combination and local adaptation embodies CPC’s spirit of “seeking truth from facts”. Following this spirit, the waterworks has been actively leveraging the state-of-the-art technologies and emerging technologies to benefit the people and the society. It is truly a role model of China’s infrastructure construction in the new era.
