How to ensure the quality of urban water supply

Days of high heat, so that the city's electricity consumption record, at the same time, water consumption is also rising. On July 31, the daily water supply of seven water plants under Nanjing Water Group reached 2.115 million tons, the highest ever in summer. How to guarantee both quantity and quality of urban water supply under "baking test"?

Is the water supply keeping up? Not only "enough", but also "space"

Last year, the city's daily summer water supply peaked at 1.89 million tons. Since July 15 this year, the daily water supply of the main city has exceeded 1.9 million tons for several consecutive days, especially recently, it has exceeded 2 million tons for many times. On July 31, Nanjing's daily water supply reached 2.115 million tons, including 2.052 million tons in the main city, a record high.

There are 7 water works under the Municipal Water Group, namely Beihekou Water Works, Chengnan Water Works, Shangyuanmen Water works, Chengbei Water Works, Longtan Water works, Yanyao Water Works and Pukou Water Works. The service scope covers the main city, Baguazhou, part of Jiangbei area and Gaochun. Chen Zhenhai, minister of production management, said that the design capacity of the seven water plants is currently 2.412 million tons per day, which can not only meet the current demand, but also has some space for storage. Moreover, from last year to this year, the Water Group has successively implemented the advanced treatment and renovation of the Shangyuanmen Water Plant, the advanced treatment and expansion of the Chengbei Water Plant, the advanced treatment and expansion of the Pukou Water Plant, and the advanced treatment and renovation of the Beihekou Water Plant. When these projects are completed, the daily water supply capacity will increase by another 250,000 tons. At present, the supply pipelines of major water plants have realized interconnection, and the dispatching center can scientifically dispatch and timely supply according to the demands of each district, so as to realize the balance of water supply.

Beihekou Water Plant, the city's largest water plant, has a total design scale of 1.2 million tons, and half of the main city's water supply comes from here. The daily water supply of the plant in summer is generally more than 900,000 tons, the highest last year was 980,000 tons, and on July 31 this year, it broke through one million tons, reaching the highest in the past year. The person in charge of the water plant told reporters that although the water supply of 1 million tons has not reached the limit of the design scale, but Nanjing water was "in the morning and evening concentrated outbreak, noon and early morning gentle" pattern, up and down, in the peak period of water, water plant filter, sedimentation tank, clear pool has been close to full load. To this end, they plan ahead, dig deep, as early as the beginning of the year launched the summer guarantee program. In March, the valve failure was checked, and the filter valve was replaced with electric valve. In May, the old units in the pump room were updated, and various electrical appliances were maintained and tested to ensure that the machine could withstand the test when summer came.

On August 2nd, the reporter saw in the Beihekou Water plant control center that all the plant rooms were in the monitoring range, and the fault alarm immediately notified maintenance. The large screen showed 19 failure points. "Most of them are minor. Now the control equipment is generally intelligent, sensitive to high temperature, as long as the manual reset is no problem." In addition to daily inspection, the plant also set up an emergency center, the implementation of 24 hours on duty.

Flood season water turbid, Yangtze River intake safe? 24 hours monitoring, adjust the process at any time

During the flood season this year, heavy rains have been falling in the middle and upper reaches of the Yangtze River. Beihekou water plant is located at the intake of Jiajiang River. The turbidity of water quality is 50-60NTU at ordinary times, and it is normal to exceed 80NTU after entering flood season. Turbidity can reach 100-200ntu during rainstorm or flood discharge from the Three Gorges Dam. Does rising turbidity affect the quality of tap water?

"No matter how high the turbidity is, it will not affect the quality of tap water entering people's homes." Beihekou water plant responsible person said, in order to ensure the safety of water quality, each water intake has video monitoring, accept the center control platform online monitoring. The automatic transmission equipment detects the water quality continuously for 24 hours, and the test data is displayed on the smart monitoring screen in real time. The turbidity was 60NTU at the time of the interview.

"Testing turbidity and ammonia nitrogen content is based on these two data to determine the construction process. For example, if it exceeds 80NTU, it is necessary to increase the frequency of sludge discharge, increase the amount of alum, and increase the process to ensure that the water quality is always above the national standard." "In recent years, with the increasing protection of the Yangtze River and the relocation of production units and buildings along the river, the water quality of the source area has been effectively guaranteed. The water quality of the water intake along the river is maintained at the level of the second-class surface water all year round, which is better than the national standard."

Is there room for further improvement of tap water quality? The reporter learned that by the end of this year, the seven major water plants will complete the deep treatment transformation, promote the water quality of our city on a higher level.

The 200,000-ton advanced treatment project of Shangyuanmen Water Plant has been tested. Project leader told reporters, in the past process, the water out of the sedimentation tank directly into the V-shaped filter, deep treatment and transformation, between the two new ozone contact pool, activated carbon filter, to achieve higher purification, "now the tap water has become from 'qualified water' into 'quality water'".

How to ensure that the main pipe is clean? Replace the new material and clean the end

High-quality tap water from the water plant, through the extensive water supply network before delivery to each household taps. However, due to the different materials and years of water supply pipes, the quality may be different. How to ensure safety in transportation?

City water group pipeline management director Pan Yuling told reporters, the past municipal water pipe materials including old cast iron pipe, cement pipe, galvanized pipe, PVC pipe, etc., these materials with the increase of service life, underground changes, there may be corrosion, leakage, damage and other problems, resulting in secondary pollution of water quality. Therefore, they will arrange personnel inspection every day, including the inspection of dark spots, timely repair damage.

Combined with the construction of municipal roads and the environmental improvement of old residential areas, the water group will replace about 40 kilometers of old water mains every year. Up to now, the new material water main pipe has accounted for more than 80 % of the total amount of the city. These pipes are mainly ductile iron pipes and PE pipes. Ductile iron pipes have the essence of iron, the performance of steel, corrosion resistance, sealing performance and compression resistance. As a kind of plastic material, PE tube has high toughness, chemical corrosion resistance, and is not easy to scale and breed algae bacteria. This year, the city also plans to clean the end area of the old pipe network. For the pipe network that has not been planned for the time being or cannot be replaced for other reasons, the first batch of more than 20 residential areas have been scheduled to be cleaned and the old scale removed.

Online articles said that every morning should open the tap empty for a period of time before use, pipe overnight water had better not drink. But is it really the case? Pan said that the water supply pipe is an airtight space, and the water quality will not be a problem because chlorine gas is added to kill bacteria. Our city factory water and water quality to the household are in the forefront of the country, with the main water pipe replacement of new materials, in the future, it is not impossible to turn the tap to drink directly. Given that the pipes installed after the water meter enters the household are installed by residents themselves, he advised citizens to buy materials with guaranteed quality, ask for product certificates and health permits from businesses, and pipe materials need to meet drinking water standards.

When does the old community need to drink water tank? Secondary water supply upgrading has been completed in 572 residential areas

Water supply enterprise network water first flow into the community tank, pool, and then through the pump pumping pressure to each household, known as the "secondary water supply". In old residential areas, due to the water supply facilities did not comply with the standard construction, or late maintenance and management, or cleaning and disinfection is not in place, there are widespread internal pipe network leakage, water pressure instability phenomenon, but also there are water quality secondary pollution hazards. Water supply transformation and direct water supply have become urgent needs of residents in these communities. Did they get their wish this summer?

The reporter learned that, in order to completely solve the "urban disease" of secondary water supply, let the people drink the "relaxation water", the municipal Party committee and the municipal government attach great importance to the reconstruction of secondary water supply facilities in the old residential areas as an important matter of people's livelihood to promote, the development of the six districts of the main city "secondary water supply transformation of the three-year action plan". From 2015 to 2017, the city has carried out secondary water supply renovation in 572 old residential areas, involving about 200,000 households and 600,000 residents.

The transformation of this round of secondary water supply facilities is a comprehensive transformation from the secondary water supply pipeline to the pool (box) and pumping station: the old concrete pool and water tank are abolished, and the corroded and aging cast iron pipes, galvanized pipes and other outdated pipes are replaced by new healthy and environmentally friendly pipes. If the conditions for direct water supply are met, water supply shall be provided by direct pumping; New water tank all use food grade stainless steel water tank; If the conditions are met, the water meter shall be used at the same time; Stainless steel water tank by the water group organized personnel regularly cleaning, testing water quality, water safety of residents has been effectively guaranteed.

Due to the high terrain or in the end of the pipe network, there are still some residential areas in the main city in the low water supply area. By the end of 2018, the city had completed the renovation of 30 low-pressure areas, benefiting more than 10,000 households and realizing the double improvement of water pressure and quality.

We will continue to strengthen areas of weakness in improving people's wellbeing. Reporters learned that this year, the water group will also promote the scope of Jiangbei New Area within the secondary water supply renovation work, a total of 9 residential areas, involving about 5500 households. At present, part of the community has completed the project and will start construction soon, so as to benefit the residents.

Article source: Nanjing Daily