Organic Phosphorus Removal By Chemical Precipitation Method From Circulating Water

In order to prevent the produce of scale and pipes corrosion in the circulating water system,the scale and corrosion inhibitor is commonly added to the wastewater,generally,the mostly choice is organic phosphorus corrosion inhibitor.However,it brings a new problem that the TP concentration in the effluent increases which leads to beyong the discharge standards.Therefore,some measures should be taken to remove organic phosphorus from circulating water.Nowadays,first step is that degrade the organic phosphorus into inorganic phosphorus by methods of photocatalytic degradation,ozone degradation and so on,and then add the corresponding chemicals,which is the common way used by the factories.But this method is characterized by narrow range of applications and complex steps,also with high cost.Considering that,a chemical precipitation method is proposed to treat the organic phosphorus wastewater in this research,that is,directly addition of calcium salt,iron salt or aluminum salt to remove organic phosphorus.The optimal conditions were determined by comparing and analyzing the effect of different chemicals on phosphorus removal,and the mechanism of phosphorus removal was analyzed.The main conclusions are as follows:1.The study on effect of five kinds of chemicals which include ferrous sulfate,ferric chloride,aluminum sulfate,polyaluminum chloride,calcium hydroxide on organic phosphorus removal was conducted.The experimental results shown that calcium hydroxide was eliminated first due to the concentration in the effluent reached to 3.826mg/L,much higher than 0.5mg/L.The first four chemicals performed well,and the effluent concentrations of 0.489,0.462,0.423,0.460mg/L,respectively,were standard.2.Improve the test method by combining calcium salt with iron salt or aluminum salt,as a result,water concentrations were standard,and the numerical difference was small.Considering the cost-effectiveness of phosphorus removal,the cheaper ferrous sulfate was selected as the best chemicals.Based on the studies of affecting factors,including dosge and reaction time,optimal conditions were confirmed as follows:the addition of calcium hydroxide was 0.052g,the concentration of ferrous sulfate 1.0 g/L,and reaction time 8 min,with high removal rate which could reach to 95.9%.3.Under the optimum condition,the removal effciency of organic phosphorus wastewater mixed by ATMP,HEDP and PBTCA in proportion was more than 94%,and the effluent concentration was less than 0.5mg/L.It was well demonstrated that the optimum reaction conditions were equally applicable to the treatment of wastewater containing multiple organophosphates.4.According to infared spectrum,the structure of the precipitate was analyzed and the mechanism of phosphorus removal was explored.The conclusion was that the organic phosphorus was physically adsorbed.5.A series of experiments on actual wastewater were conducted under the optimum condition,in order to enhance removal efficiency.Two ways,addition of hydrogen peroxide or aeration,were tried.It was found that when the hydrogen peroxide was 36mg/L or the aeration time was 8min,the effluent phosphorus concentrations were less than 0.5mg/L,meet discharge standards.6.The effects of common co-existing ions on the removal efficiency of organic phosphorus were studied.It was showed that Mg²⁺?NH⁴⁺ and SO₄^2-in high concentration had definitely inhibiting function on removal efficiency.While Cu²⁺ could promote the removal of organic phosphorus.And Zn²⁺ and Cl^- had on influence.In summary,the means by combining calcium hydroxide with ferrous sulfate,without pre-oxidation,is adopted to deal with organic phosphorus wastewater,which effect of wastewater treatment are both significant regardless of synthetic wastewater or actual wastewater.This method has the advantages of simplification,low cost,and no secondary pollution,which provides a new method for the removal of organic phosphorus and has practical significance and application value in industrial circulating water treatment.