Research On The Application Of Residue&Soil Phosphorus Removal Composite In Advanced Treatment Of Eutrophic Water

Eutrophication has become a global environmental problem.Exploring the causes of eutrophication,researching treatment strategies and developing new treatment technologies have important practical value and significance for the treatment,maintenance,and sustainable development of eutrophic water bodies.The development of economical,efficient and recyclable adsorbent materials for the deep dephosphorization of eutrophic water bodies is of great significance for controlling the eutrophication degree of rivers,lakes and other waters,reusing industrial waste residues,and realizing the recycling of phosphorus resources.We mixed the activated clay with two kinds of industrial waste residue(steel slag and fly ash)as adsorption substrate,with binder and porogen to make the Residue & Soil Phosphorus Removal Composite(RSPRC).The main research results of this article include:(1)We studied four methods for modifying industrial waste slag substrates(steel slag and fly ash).The results show that the best method for steel slag was 800 ℃ high temperature modification,and 0.3 mol/L Fe Cl3 solution modification for fly ash.And after adding activated clay,the material’s decolorization,phosphorus removal performance and the optimal ratio were studied,and the optimal mixture ratio of RSPRC was determined to be 74.5: 10.5: 10: 5(fly ash: steel slag: activated clay: cement).(2)Static adsorption and dephosphorization experiments were carried out.The results showed that the maximum saturated adsorption capacity of RSPRC at 15 ℃,25 ℃ and 35 ℃ was 6.652 mg/g,6.987 mg/g and 7.405 mg/g,respectively.And the adsorption process conforms to Langmuir isotherm adsorption model;ΔG0<0 indicates that the adsorption on phosphorus spontaneously occurs,ΔH0>0,indicating that the adsorption on phosphorus is an endothermic process.At different temperatures and different initial concentrations,the adsorption process conforms to the quasi-second-order kinetic model better.(3)The influence of temperature,particle dosage,initial phosphorus concentration,p H,adsorption time and ammonia nitrogen is the on the dephosphorization of RSPRC were studied,and the stability of adsorption was investigated.The results showed that the adsorption capacity of RSPRC increased with increasing temperature;The adsorption capacity of RSPRC increases with the increase of the initial phosphorus concentration;and the adsorption capacity increases with the increase of the adsorption time.At the beginning,the adsorption rate is very fast,and then the adsorption rate gradually slows down until the adsorption equilibrium;The removal rate was increased with the increase of dosage.With the phosphorus concentration of wastewater is 5 mg/L,the optimal dosage is 2.5g/250 mL;compared to neutral conditions,the removal rate is higher in acidic solutions,but in general,p H has little effect on the adsorption of phosphorus;ammonia nitrogen also has basically no effect on the adsorption of phosphorus,and RSPRC has a certain adsorption capacity for ammonia nitrogen.(4)Dynamic adsorption and dephosphorization experiments were carried out.The influence of inlet flow rate,concentration and filler mass on bed penetration time were studied.The penetration time becomes shorter as the inlet water flow increases.The amount of treated water in the adsorption column before the penetration increases first and then decreases with the increase of the inflow rate.The maximum amount of treated water is 2.5 m L/min;the higher the influent concentration,the shorter the penetration time of the adsorption column and the less the treated water;the more the filler mass,the longer the penetration time of the adsorption column and the more the treated water.PRSPRC runs more stably under lower load and is suitable for processing low-concentration phosphorus-containing waters.Under the conditions of initial phosphorus concentration of 5 mg/L,inlet flow rate of 2.5 m L/min and filler mass of100 g,the RSPRC adsorption column has a good adsorption performance for phosphorus during the operation period,and the phosphorus concentration in the effluent was kept below 0.2 mg/L within 59 days.(5)A laboratory simulation of the real water phosphorus reduction experiment was conducted.The results showed that under the simulated river flow conditions,when the particle dosage was 250 g and the hydraulic retention time was 3 d,the phosphorus removal rate fluctuated in the range of 20% to 27%.The phosphorus concentration in the effluent can be stabilized at about 0.2 mg/L.At this time,increasing the hydraulic retention time has little effect on the phosphorus removal effect;When the dosage of RSPRC is 500 g,the removal rate of phosphorus is kept at around 30%,and the removal rate is improved compared with the dosage of 250 g.The phosphorus concentration in the effluent is basically maintained below 0.18 mg/L,which was lower than the threshold value of 0.2 mg/L for the total phosphorus in category III water quality specified in The Surface Water Environmental Quality Standard(GB 3838-2002).Then 500 g RSPRC were placed in two groups in series.Under the same conditions,the effect of removing phosphorus was increased by about 11% compared with that of non-series.In practical applications,the removal rate of phosphorus can be increased in series;(6)An material safety analysis experiment of RSPRC was carried out.The leaching of three heavy metal ions of Zn,Cu and Fe in the water after treatment was tested,and all of three reached the discharge standard.The wastewater treated by RSPRC will not produce secondary pollution of heavy metals and can be safely discharged;and experiments were carried out on the stability of adsorption.Through the desorption experiment under the conditions of clean water,hot water and strong acid,it was found that the desorption rate of RSPRC in hot and clean water is extremely small.In sulfuric acid solution,phosphorus is easily desorbed from RSPRC.The desorption rate is increased with the enhencement of sulfuric acid concentration,which can reach more than 99%.The results provide a reference for phosphorus desorption and recovery.