Example of Wastewater Regeneration and Reuse in St. Petersburg, Florida

St. Petersburg is the fourth largest city in Florida, with 250000 residents and thousands of seasonal visitors. That's rightOne of the ways to reuse urban wastewater. In 1977, the municipal government decided to implement "*" and began using recycled water for non drinking purposes in 1978. A dual distribution system was implemented, which provides users with two different qualities of water (drinking water and non drinking water) through two independent distribution systems. Currently, recycled water is provided to more than 7000 households and office buildings in the city, with a capacity of 80X10m3/d in 1991, for use in scattered households, parks, school playgrounds, golf courses, and apartments as garden irrigation, air conditioning cooling water, and firefighting water·

There are a total of four in this citysewage treatment plantThe treatment plant is located in the four corners of the city, and the recycled water pipes form a large irregular pipeline transportation system in the city center. In this system, the large pipe diameter is about 1067 tnm, most of which are less than 914 mrn. Therefore, large-scale excavation is generally not required, which is also a factor in saving the cost-effectiveness of the recycled water system. Another advantage of discharging all four sewage treatment plants into a large system is that when one or two of them stop running for some reason, there are still two or three that are running normally, which can reduce inconvenience to users. The total treatment capacity is 270X10 ^ 3m3/d, using activated sludge biof technology, and adding aluminum salt coagulation, filtration, and disinfection treatment. The dual pipe water supply system pipeline is 420km long. (Pipe diameter 50~1200mm), use 10 deep wells to feed excess recycled water into the aquifer On average, 60% of recycled water is injected into deep wells during a year, saving water. Therefore, although the daily population in Hai City has increased by 10%, it can still meet the supply of drinking water. Table 10-3 shows the treatment capacity of sewage treatment plants in 1995

In order tosewage treatment plantThe outflow of water into surface water bodies reaches *, and St. Petersburg has built a deep well reinjection system to dispose of the remaining water. According to Florida regulations, these wells are classified in the classification. These wells are only used when the storage tank is full or the produced water does not meet the high-quality reuse standards set by the city, and there is surplus water. The water quality standards for recycling and reinjection well water: free residual chlorine<4.0mg/L, turbidity 2.5NTU, SS5mg/l, C1-600mg/l