Migration And Transformation Of Inorganic Phosphorus In Municipal Reclaimed Water

In recent years,with the increasing shortage of fresh water resources,the reuse of municipal reclaimed water in industrial circulating cooling systems is an important measure to solve the water shortage problem.Municipal reclaimed water has the characteristics of stable water quality,reliable sources and no need of long-distance water diversion,but its complicated water quality will bring serious problems such as fouling,corrosion and microbial growth to the circulating cooling system.Higher content of phosphorus is an important factor in increasing system scaling,corrosion and microbial growth.In this paper,particulate inorganic phosphorus in municipal reclaimed water was taken as the research object.The migration and transformation rules of particulate inorganic phosphorus in simulated circulating cooling system and its influence on scale and corrosion of the system were studied by designing and setting up experimental devices.Molybdenum antimony anti-spectrophotometry and the M-SMT method improved by our group were used to determine the content of dissolved inorganic phosphorus in the system and the morphology and content of particulate inorganic phosphorus in the scale while the scaling and corrosion in the system were also analyzed.Then the rules of migration and transformation of particulate inorganic phosphorus in simulated circulating cooling system and its influence on scale and corrosion of the system were summarized.Migration and transformation studies show that temperature and hardness are the main factors affecting the migration of particulate inorganic phosphorus.With the increase of temperature,the solubility product of insoluble matter decreased and the mobility of particulate inorganic phosphorus increased by about 11%;With the increase of hardness,the scale-forming ion product increased and the mobility of particulate inorganic phosphorus increased by about 17%;Concentration rate,particulate inorganic phosphorus concentration and flow rate had little effect on the migration of particulate inorganic phosphorus,the increase of concentration ratio and concentration of particulate inorganic phosphorus led to a slight increase of the mobility of particulate inorganic phosphorus,the increase of flow rate led to a slight decrease of the mobility of particulate inorganic phosphorus,and the variation of mobility was about 5%.The conversion of granular inorganic phosphorus was affected by different conditions.The conversion rate of weakly adsorbed phosphorus was mainly affected by the flow rate,the increase of the flow rate led to the decrease of the weakly adsorbed phosphorus conversion rate;The conversion rate of aluminum-bound phosphorus was mainly affected by the flow rate and temperature,the increase of flow rate was helpful to promote the transformation of Al-bound phosphorus while the increase of temperature hindered the conversion of Al-bound phosphorus;The conversion rate of Fe-bound phosphorus was not affected by water quality and operating conditions,and its conversion rate was basically stable at about 14%;The Ca-bound phosphorus was mainly affected by temperature and hardness,the increase of temperature and hardness were all conducive to the promotion of Ca-bound phosphorus conversion.Fouling and corrosion in the simulated circulating cooling system were aggravated by migration and transformation of particulate inorganic phosphorus.The migration of particulate inorganic phosphorus promoted the fouling in the system,which led to the increase of the fouling amount in the system.Meanwhile,the system corrosion was aggravated by the increase of the fouling amount.The larger the fouling amount was,the more serious the corrosion was and the maximum corrosion rate was 0.015mm/a fouling amount was 2.76 g when the fouling amount was 2.76 g.The specific mechanism of the effect of particulate inorganic phosphorus on system corrosion was unclear.The change of phosphorus content in Al-bound phosphorus and Ca-bound phosphorus could be one of the influencing factors.The increase of phosphorus content in Al-bound phosphorus and Ca-bound phosphorus could increase the system corrosion.