| The excess sludge and the fly ash are the most common solid wastes in the world.Both of them are the inevitable products in the process of urban industrialization.The huge production of them does imcalcuable threat to the ecological environment,climatic conditions and even human health.At the same time,the eutrophication of water environment in China still exists while becoming more serious,and the poor quality of environment directly restricts the sustainable development of society and economy.The first priority of the governance and even the avoidance of urban eutrophication of water is to reduce the N,P and other elements of the content.Therefore,this paper was based on the huge discharge of the sludge and coal fly ash,the urgence to treat as well as the treatment situation of the low concentration of ammonia nitrogen wastewater.In view of the requirements of the filter,unburned and burned ceramsite were prepared by sludge from Wuhan Shahu water plant and fly ash from Qingshan thermal power plant.According to the difference of the performance of the two different sludge ceramic filters,the burned sludge ceramsite was modified for the treatment of medium-low concentration ammonia nitrogen wastewater,and the feasibility of agriculture of the unburned after absorbing the waste water was also studied.The organic combination the above aspects not only solve the outbound pressure of the excess sludge and fly ash,but also alleviate the harm casused by the emission alone,the high costs of the filter applied to the treatment of the ammonia nitrogen waste water and even alleviated the problem of the disposal of the ceramsite waste after saturated saturation.More importantly,to a certain extent,the realization of the remaining sludge of the resource,reduction and stabilization,successfully explored an effective way of t "waste to waste,turning waste into treasure",the specific conclusions are as follows:1.The formula and performance indicators of the homemade ceramsite.1)The best recipe for unburned ceramste was fly ash 70.9%,calcium oxide 7.1%,sludge 7%,NaHCO31%,cement 9%,34g water/100g dry material,and water glass 5%.After granulation the maintenance method used in this experiment was:wet gauze for 24h at room temperature,then steam curationg for 16h at 80?,and finally used the oven to dry at 105?.The main performance indexes of the products were as follows:the specific surface area was 17.038m2/g,the crushing rate and the wear rate were 2.2%,the bulk density was 729kg/m3,the apparent density was 1140kg/m3,the hydrochloric acid solubility was 1.66%,porosity was 41.67%,water absorption rate was 38.44%.2)The optimum formulation of burned ceramsite was fly ash:sludge:clay=3:6:1,preheated at 350 ? for 30min,and sintered at 800 ? for lOmin.The main performance indexes of the prepared burned ceramsite were as follows:the specific surface area was 2.40m/g,the sum of the crushing rate and the wear rate was 0.82%,the bulk density was 581.9kg/m3,the apparent density was 1020.41kg/m3,the hydrochloric acid solubility was 1.81%,porosity was 44.12%,water absorption rate was 60.37%.The physical and chemical indexes of the two kinds of sludge ceramsite all meet the "water treatment artificial ceramic filter"(299-2008 CJ/T),and the amount of heavy metal dissolved in the soaking solution was also related to the "Hazard Identification Criteria-Leaching Toxicity Identification"(GB5085.3-2007).Therefore,it is safe to use it as a water treatment filter.2.The optimum adsorption conditions and adsorption models of homemade ceramsite on ammonia nitrogen.1)The optimum conditions for the static adsorption of ammonia of the unburned were as follows:the dosage was 5g,the initial concentration of ammonia nitrogen was 225mg/L,pH=7,the adsorption time was 12h and the temperature was 30?.The adsorption capacity of the unburned ceramsite is 4.25mg/L.It could be seen that the Langmuir adsorption isothermal model can better describe the isothermal adsorption effect on ammonia nitrogen of the unburned ceramsite.And the adsorption process of ammonia nitrogen was in accordance with quasi-second-order kinetic model.The kinetic equation of ammonia adsorption was:t/qt=0.2003t+0.846.2)The best conditions for the adsorption of the burned was:the pottery dosage was 10g,the concentration of ammonia is 100mg/L,pH=9,the adsorption time was 18h and the temperature was 30?.The sintered ceramsite is slightly 0.481mg/L.The Langmuir adsorption isothermal model can also better describe the isothermal adsorption effect on ammonia nitrogen.And the adsorption process of ammonia nitrogen was as well as in accordance with quasi-second-order kinetic model.The kinetic equation of ammonia adsorption was:t/qt=0.83 78t+4.0899.3.Study on modification and treatment of burned ceramsite in low concentration ammonia nitrogen wastewater.1)The optimum modification scheme of burned ceramsite was determined by orthogonal test.The concentration of the NaOH solution was 2mol/L,the solid-liquid ratio was 1:6,the modified temperature was 70? and time was 2d.2)The optimum static adsorption conditions of the modified ceramsite were as follows:the dosage of the filter was 10g,the initial concentration was 300mg/L,pH =3,the adsorption temperature was 20 ? and the adsorption time was 8h.Compared with the unmodified ceramsite,the adsorption capacity was greatly improved,reached 2.25mg/g.The adsorption of ammonia nitrogen is in accordance with Langmiur isothermal model and quasi-second order kinetic model.The isothermal equation was1/Qe=68.505 1/Ce-0.2614,and the kinetic equation was t/qt=0.035 + 0.45t?3)The optimum regeneration conditions of the ceramsite treating 25mg/L ammonia nitrogen wastewater were as follows:the regeneration agent was NaCl and NaOH with the ratio of 1:2,the solution was of 5g/L,the regeneration temperature was 75 ?,the pH was 7 and the time was 6h.4)The dynamic treatment effect,penetration and its regeneration rate were studied by using 25mg/L ammonia nitrogen wastewater.the effective treatment of water from the first 6.4L to the second 4.6L and then reduced to the third 2.9L,penetration time from 8h to 6.5h and then to 5h,the modified sludge ceramsite reproduction rate decreased from 71.9%to 45.5%.4.Feasibility study on agriculture of ceramsite residue after treating the domestic sewage.In order to explore the feasibility of the homemade unburnedceramsite(SSA=17.038 m2·g-1)after processing the sewage for agriculture,they were used as cultivation substrate to cultivate brassica chinensis.At the same time the influence of seed germination rate,the growth and the yield were studied.First,the results showed that the heavy metals such as Cr?Cd?Hg?As?Pb and the nutrients like TN?TP?TK and the organic matter were within the national standard GB8172-87,which proved the waste ceramsites could be recycled.Then,the ceramsites were mixed with the soil according to the six different proportions:0%?10%?20%?30%?40%and50%.The influence is obvious,the brassica chinensis become more pest-resistant and lodging-resistant.It increased as high as 59.69%when the proportion was 20%.However the higher the proportion is,the weaker the drought-resistance is,and would also inhibits the seed germination as well as growth. |
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