Reclaimed water is called "reclaimed water" in sewage engineering and "reclaimed water" in industrial utilization, which mainly refers to non-potable water that can be reused within a certain range after urban sewage or domestic sewage reaches a certain water quality standard after treatment, and its water quality is between tap water and sewage discharge. Reclaimed water reuse can reduce the discharge of treated urban sewage and correspondingly reduce the pollution load on the water environment, which is the manifestation of cleaner production, and is also the concrete embodiment of sewage recycling, and is an important way to solve the shortage of water resources. Because the water source treated by reclaimed water is urban sewage and domestic sewage, the content of phosphorus, ammonia nitrogen, organic matter, and some even heavy metals is high, and the water quality of reclaimed water fluctuates greatly with seasonal changes. Reclaimed water reuse Reclaimed water can be used as circulating cooling water, mainly with the following characteristics:
1) The suspended solids in the water have a large change amplitude, and it is easy to deposit and form dirt in the circulating water system, which promotes the deposition of dirt and leads to local corrosion. Therefore, the requirement for circulating water and make-up water is that the lower the turbidity, the better.
2) The water hardness is large, especially the calcium hardness is high, which brings great difficulties to the operation of the high concentration rate of circulating water. When the hardness of circulating water is too high, it will interact with carbonate, phosphate or silicate in the water to form calcium carbonate, calcium phosphate and magnesium silicate scale. The calcium ion content in the water accounts for a large proportion, because the calcium ion is a scaling ion in the circulating water system, and the calcium carbonate precipitate can be formed after heating, so when the circulating cooling water is treated, the concentration rate needs to be controlled, and the acid addition method is adopted if necessary to reduce the possibility of scaling as much as possible.
3) The total phosphorus content of the reclaimed water is between 2 and 3 mg l, so the phosphorus content should be controlled during the screening of water quality stabilizers.
4) The organic matter content in the water is high, and the content of CODCR is 3 60 mg L. The control of organic matter in circulating water should not be too high, and the treatment of microorganisms should be strengthened to control the growth of organic matter and prevent the growth of slime from causing corrosion under scale. Sterilization should be considered when the organic content is high.
5) The content of sulfate and chlorine in the water is very high, and the sum of these two ions is generally controlled to be less than a certain value, otherwise the attachment will be locally concentrated on the surface of the heat exchanger, resulting in local corrosion.
According to the characteristics of the above-mentioned reclaimed water, and according to the water quality, it was decided to use its low phosphorus agent for treatment, and the scale inhibition focused on the formation of CaCO3 scale, and at the same time, due to the large range of turbidity change of the make-up water, it was necessary to choose the scale inhibitor and dispersant with good dispersion effect on the scaling factor and slime. Through the results of the screening test of antiscalant monomers, it was found that PBTCA, phosphosulfonic acid and AA-AMPS copolymer antiscalants showed good dispersion, which would be of great help to overcome the problem of high turbidity of circulating water, and the phosphorus content of PBTCA and phosphosulfonic acid was low, so these three monomers were selected as the compound antiscalant monomers.
According to the results of the antiscalant monomer screening test, AA-Amps copolymer was selected: 10 mg L; pbtca：3mg/l；Phosphosulfonic acid: 45mg/l。The phosphorus content in this complex formula is 1 15mg/l。Through a certain scale inhibition and corrosion inhibition measurement, it is recommended to add acid to adjust the pH of the water sample to 83~8.8. Consideration of safety should be in 3Run at concentrations of less than 5x.