Experimental Study On Remineralization Process Coupled With Carbon Dioxide And Lime

The Pearl River downstream water quality presents the characteristics of low hardness and alkalinity, poor chemical stability and highly corrosive. The current water quality stability method can not meet the rising water quality requirements. In this paper, to B raw water as the research object, the study on remineralization technology with carbon dioxide and lime was carried out on the basis of a full investigation for chemical stability of water supply system in Shenzhen, major findings are as follows:1. By the survey and analysis of water quality of five waterworks in the city of Shenzhen for up to two years, it is concluded that the raw water, off-work water and water in pipe network perennial corrosive. The chemical stability of water in pipe network has great relevance of off-work water, so it is very important to control the stability of off-work water.2. The additive lime treatment process, which can improve the stability of water-carbonate system, but the effect is limited, off-work water and water in pipe network is still corrosive and lime dosing alone cannot control water larson ratio.3. Carbon dioxide and lime coupled to remineralization technology can greatly improve the water total alkalinity and calcium hardness. Different dosage of carbon dioxide and lime has significant effects on pH and four judge indexes in water carbonate system as LSI, RSI, CCPP and AI. And the change rule of four judge indexes is similar to pH with the dosing quantity. So it is conclude that the pH is the main influence factor on the water quality stablility of the water-carbonate system. With Carbon dioxide30mg/L, lime34mg/L, Larson ratio will be under control at0.4, each index of water-carbonate system to be inacceptable level, and this dosing quantity suitable for Shenzhen’s raw water.4.The Lime dosing point influence coagulation precipitate great, former additive lime, coagulation precipitate best effect. The dosing of carbon dioxide with lime changes the pH value, thus water of coagulation precipitate and filtering effect affected. When carbon dioxide30mg/L, lime dosing in30-40mg/L, coagulation precipitate and filtering effect is good. The hardness and alkalinity of the water has no obvious effect on the process of water treatment.5.Compared with NaHCO3, NaOH, Na2CO3, Ca(OH)2these four alkali agent dosing method, CO2coupled with lime process be able to meet pH, total alkalinity, water-carbonate system index and larson ratio requirement, technically a considerable advantage.