China has achieved extraordinary economic growth during the past twenty years, reducing poverty and raising the standard of living. However, this rapid growth has caused negative environmental side-effects. Industrialization and urbanization have increased water pollution and caused severe surface and groundwater supply problems, especially for rural communities.
Challenge: Many of Zhejiang Province's 35 M Residents Lack Access to Clean Tap Water
The residents of the Zhejiang Province represent one of many rural regions suffering from water scarcity. For decades, tourists from all over the world have paid homage to the ethereal Zhejiang Province, located on the southeast coast of China. Su Shi, an eminent poet of the Song Dynasty (960-1279) once said of Zhejiang, "Rippling water shimmers on a sunny day and misty mountains are wonderful in the rain." Unfortunately, the region's formerly clear waters have become polluted by untreated sewage, pesticides and fertilizers, and have been rendered unsuitable for drinking.
Today, twenty percent of the rivers in the Zhejiang Province have become classified as "severely polluted." In fact, thirty percent of the 35 million residents of the Zhejiang Province do not have access to clean tap water. Consequently, these ten million people in farming communities have to drink untreated water from rivers, lakes, ponds, and wells - water that not only tastes bad, but is also highly contaminated and poses serious health risks.
Solution: Government Funds Largest UF/RO Water Plant in China
To address these issues and satisfy their needs, the provincial government is investing more than 20 billion yuan, or some 2.4 billion U.S. dollars, in new water projects that aim to ensure all of Zhejiang's rural residents have access to clean drinking water by 2012.
The Zhejiang Chixi Hangfeng Water Plant is a major component of this initiative. The water treatment plant, constructed in November 2004, is located in the small city of Chixi, which is 400 kilometers south of Shanghai. The plant is the largest water plant in China to use ultrafiltration (UF) and reverse osmosis (RO) membrane systems for the production of potable water. Built by China BlueStar Water Treatment, Co., Ltd, the Zhejiang plant has a total capacity of 1200 cubic meters/hr.
"This project marks a monumental step in the prevention of water scarcity in China," remarks Mr. Wang Yutong, the General Manager of BlueStar Water Treatment. "We are pleased to leverage the power of membrane technology to provide the Zhejiang Province residents with access to clean drinking water and a better quality of living."
The Technology: UF as Pretreatment to RO
The incoming feed water for Zhejiang Chixi Hangfeng Water Plant comes from a heavily polluted reservoir which is frequently tainted with salt water from the nearby coast. To purify the water, China BlueStar decided upon an advanced UF/RO membrane solution from Koch Membrane Systems, Inc. (KMS), a leading developer and manufacturer of membrane filtration systems.
"We selected KMS for its longstanding expertise in membrane filtration and separation technology, said Mr. Qian Junbao, the Chief Engineer of the Zhejiang Plant. "It was crucial that the membranes be extremely reliable and were constructed with highest quality in order to successfully execute this challenging task."
The combination of RO, with UF pretreatment, is ideal for the treatment of heavily polluted brackish water. For reverse osmosis, the plant installed 192 of the KMS TFC8832-575 Magnum® reverse osmosis elements. These high performance elements utilize a proprietary thin film composite polyamide membrane specially designed for brackish water treatment. Reverse osmosis for brackish water treatment is a moderate-to-high, pressure driven process for separating larger size solutes from aqueous solutions by means of a semi-permeable membrane. Salt rejection with RO can reach or exceed 99.5%. Since most dissolved and suspended material is rejected by the membrane, the RO permeate is purified water.
One of the primary benefits of reverse osmosis when compared to the conventional ion exchange method of desalting water is the reduction in chemical use and waste disposal costs associated with the regeneration of ion exchange resins. Additionally, RO systems are much less labor intensive. However, there is a vulnerability to solids plugging which can be greatly reduced with pretreatment such as ultrafiltration.
Ultrafiltration membrane systems have several attributes that make them ideally suited for the pretreatment of feed water to spiral RO membranes in brackish water treatment plants, such as the Zhejiang Chixi Hangfeng Water Plant. One of the main benefits of UF systems is cost efficiency.
"KMS UF systems are cost competitive with conventional chemical based water pretreatment operations and they require significantly less floor space and can have lower labor, chemical, and waste disposal costs," said Mr. Qian. The use of large diameter UF cartridges with thousands of hollow fibers that pack a great deal of membrane surface area into a small space contributes to the compact system design that takes up less plant space.
KMS UF membranes are able to consistently deliver product water with very low turbidity (to less than 0.1 NTU) and very low Silt Density Index (SDI between 1.0 and 3.0). Moreover, because the filtration is a function of the membrane pore size and particle geometry, consistent product water quality is achieved.
Therefore, KMS UF membranes enable more reliable and less expensive operation of a downstream reverse osmosis system, especially when there are limited operating resources.
UF Membrane Construction
China BlueStar installed 160 hollow fiber TARGA®-10 UF cartridges from KMS, each cartridge measuring 10" in diameter and 72" in length and containing a total of 870 square feet of membrane. The 10" diameter cartridges provide 60% more membrane area than conventional 8" diameter cartridges and produce 60% more product water.
KMS hollow fiber (HF) membranes were selected over spiral membranes for this application because they can operate at higher levels of suspended solids. The HF membranes have open feed channels and are periodically backflushed with clean, filtered water to control the buildup of solids on the surface of the membrane. The flow through KMS hollow fibers is from the inside to the outside, meaning that the filtered water passes through the fiber wall to the outside, while the solids remain on the inside.
The KMS TARGA-10 cartridges utilize polysulfone membrane material, which offers distinct advantages when it is time to clean. It can handle a broad pH range, from 1.5 to 13, and it can tolerate up to 200 ppm of chlorine.
Results: Polluted Feed Water Becomes High Quality Drinking Water
The Zhejiang Chixi Hangfeng Water Plant has been up and running for almost one year. The plant has been highly successful as a cost effective and easy-to-maintain process, turning poor quality feed water into consistently high quality drinking water, and the residents of Zhejiang are very grateful.
"We receive positive feedback on a regular basis," said Mr. Qian. "It's so nice to know that this plant has improved the quality of life for so many people."
Because of its monumental success, the Zhejiang plant now serves as a model for new water treatment facilities throughout China. During the current year, the number of plants using 10-inch UF cartridges in China is expected to more than double, from seven to more than fifteen. The capacity of the Zhejiang Chixi Hangfeng Water Plant alone will be expanded by 300 percent during the next five years, as the province is aggressively working to meet the drinking water needs of its rural residents.
While water scarcity in China is not nearly over, treatment plants utilizing membrane technology are rapidly increasing, and communities like Zhejiang Province are beginning to see a light at the end of the tunnel.
Author/Title: Mr. Ruming Pang, Koch Membrane Systems, Regional Sales Manager, Shanghai, China
For more information contact Mr. Ruming Pang at firstname.lastname@example.org or email@example.com, call 888-677-5624 or visit their website at www.kochmembrane.com.