Optimization Of Sludge Modification In Water Treatment Plant And Its Phosphorus Adsorption Properties For Wastewater Treatment

With the sustained and rapid development of China’s social economy,the demand for industrial and agricultural production and domestic water has increased rapidly,and the number and scale of water purification plants have been increasing.The amount of sludge generated during the water purification process continues to increase.Currently,the annual sludge output of water purification plants has reached millions of tons.Once a large amount of water purification plant sludge is improperly disposed and enters the natural environment,it can damage the ecological environment and pose a potential threat to human health.Therefore,it is necessary to properly treat and dispose of water purification plant sludge.The resource utilization of sludge from water purification plants is an effective approach to its rational disposal.Adhering to the concept of"treating waste with waste",using sludge from water purification plants as an adsorbent for wastewater treatment has become a research hotspot in this field with its broad application prospects in recent years.This topic aims at the low efficiency of directly using sludge from water purification plants as adsorbent for wastewater treatment.Based on in-depth analysis of the composition and characteristics of sludge from different water purification plants,the methods for modifying sludge from water purification plants were systematically optimized,and modified sludge was used for phosphorus removal by adsorption in wastewater treatment plants.The efficiency of phosphorus removal by adsorption of modified sludge was systematically investigated,and its adsorption mechanism was clarified.The research of this topic has enriched the methods and application scenarios of sludge modification in water purification plants,with a view to providing technical support for rational disposal and efficient reuse of sludge in water purification plants.Using field research and literature research methods,12 surface water purification plants were investigated,and two representative water plants,Jinan Fenghuang Road Water Plant and Heze Yellow River Water Plant,were selected to characterize and analyze their sludge composition and characteristics.SEM analysis showed that the sludge from both water purification plants was irregular and massive,with granular,flaky,and porous structures on the surface;The specific surface area and pore volume of sludge in Fenghuang Road Water Plant are larger than those in Huanghe Water Plant,while the average pore radius is smaller than that in Huanghe Water Plant.The above differences are related to the differences in water purification processes,water sources,and types of coagulants;The X-ray fluorescence spectrum analysis results show that the basic components of the sludge from the two water purification plants are similar,both containing a large amount of Al₂O₃,Ca O,Fe₂O₃,as well as a small amount of Mg O,K₂O,Na₂O,etc.,which have the potential to be used as phosphorus removal adsorbent for sewage.The Fe₂O₃content in the sludge from the Yellow River Water Treatment Plant is higher than that from the Fenghuang Road Water Treatment Plant,while the Al₂O₃content is slightly lower,which is related to the use of polymeric aluminum iron chloride as a coagulant.The effects of p H value,dosage,reaction time,initial phosphorus concentration,temperature,mesh count,and other factors on phosphorus removal by adsorption of sludge from wet and powdered water purification plants were investigated.The results of single factor adsorption experiments show that the adsorption characteristics of phosphorus in wastewater by wet and powdered sludge from water purification plants are similar;Sludge adsorption and phosphorus removal performance is better under acidic conditions;With the increase of sludge dosage,the phosphorus removal rate increases and the adsorption amount decreases.When the dosage is large,the change rate of the removal rate and dosage becomes slow;With the increase of initial phosphorus concentration,the adsorption amount of phosphorus by sludge also increased,but the removal rate showed a downward trend;With the increase of reaction time,the phosphorus removal rate of water purification plant sludge shows a trend of rapid increase in the early stage and tends to stabilize in the later stage.Although the phosphorus adsorption capacity of powdered sludge is greater than that of wet sludge,its adsorption speed in the early stage of reaction is lower than that of wet sludge;The mesh number has little effect on the adsorption performance of sludge powder.The results of multi factor orthogonal test showed that there were significant differences in the impact of various factors on the phosphorus removal efficiency of wet and pulverized sludge adsorption in the two waterworks.The fitting results of adsorption kinetics show that the adsorption processes of phosphorus by wet and powdered sludge from the two water purification plants conform to the quasi second order kinetic model and Langmuir isothermal adsorption model,and chemical adsorption plays a major role in the adsorption process.In order to improve the adsorption and phosphorus removal efficiency of water purification plant sludge,comparative experimental studies on acid modification,thermal modification,lanthanum modification,and zinc modification of water purification plant sludge were conducted,and various modification conditions were systematically optimized.The optimal preparation conditions for each modification method were recommended as follows:acid modification of water purification plant sludge,sulfuric acid concentration of0.2 mol/L,solid liquid ratio of 1:15,and reaction time of 1 hour;For thermal modification of sludge from water purification plants,the optimal calcination temperature is 500 degrees Celsius;Water purification plant sludge was modified with lanthanum,with lanthanum chloride concentration of 0.5%,p H of 10,and reaction time of 3 hours;The sludge of the water purification plant is modified with zinc,with a zinc chloride concentration of 0.3 mol/L,a p H of 7,and a reaction time of 2 hours.SEM,BET,and XRF analysis showed that the surface of sludge from water purification plants modified by acid and heat was rougher,while a large number of flake and flocculent structures appeared on the surface of sludge from water purification plants modified by lanthanum and zinc,blocking some pores;After acid modification and thermal modification,the specific surface area of sludge from water purification plants increased significantly,and its pore volume and radius decreased,while the specific surface area of sludge from water purification plants modified with lanthanum and zinc significantly decreased;Acid modification can dissolve the iron and aluminum components in the sludge,significantly reducing the iron and aluminum content.However,lanthanum and zinc have been successfully introduced into the sludge through lanthanum modification and zinc modification,with the content of lanthanum and zinc being 7.98%and27.10%,respectively.The adsorption and phosphorus removal performance of modified water purification plant sludge was systematically investigated.The experimental results show that acid modified water purification plant sludge exhibits good adsorption performance at p H 5-11,and only at extremely low p H does it exhibit poor adsorption performance;The effect of p H on sludge from thermal modified water purification plants is similar to that before unmodification.As p H increases,adsorption performance gradually increases;The adsorption performance of sludge from water purification plants modified with lanthanum and zinc is the best at p H 3.At p H 5-9,its adsorption effect on phosphorus gradually deteriorates,but the range of change is very small.At p H 11,it decreases sharply,and alkaline environment is not conducive to its adsorption of phosphorus.According to the adsorption model fitting,the adsorption process of phosphorus by modified water purification plant sludge also conforms to the quasi second order kinetic model and Langmuir isothermal adsorption model,and chemical adsorption plays a major role in the adsorption process.After acid,heat,lanthanum,and zinc modification,the phosphorus adsorption and removal efficiency of water purification plant sludge increased by 16.78%,23.26%,41.53%,and 42.87%compared to the unmodified sludge,respectively.After zinc modification,the phosphorus adsorption efficiency of water purification plant sludge was the best.