| With the water consumption increasing quickly,the sewage treatment plants construct rapidiy and yields huge sludge.In recent years,the annual production of sludge is about 30 to 40 million tons,but its resources utilization rate is only 10%.Sewage sludge is very suitable for using as a soil conditioner,it contains a lot of nutrient elements and organic substance,could promote the growth of plant.It also contains large amounts of toxic and hazardous substances,like heavy metals and organic pollutants.It will cause serious ecological and environmental problems if processed improperly.Aerobic composting is an effective method to harmless treat,reduce and reuse sewage sludge,and sewage sludge compost is a promising means of disposal,could achieve considerable economic benefit.To study the effect of different proportions of bentonite and different kinds of alkali solids on aerobic compost,this experiment selected the sewage as raw material,sawdust as amendments,and amended with 2.5 %,5.0 %,7.5 % calcium based bentonite,and with straw biochar,hardwood biochar,fly ash and lime by 10% addition ratio in dry weight during the 52 days aerobic composting process.The main research conclusions are as follows:?1?Additives amendment prolonged the thermophilic phase,accelerated the decomposition of the organic matter.Compared with non-amended treatment,amended with proportions were more conducive to compost maturing?2?The compost p H increased at the beginning and then gradually decreased.At the end of compost,the range of p H for all treatment is 6.76-7.05.The bentonite amendment reduced the salinity of the compost and the values of EC were all less than 600 ?S·cm-1 in the end,and the GI of compost finally >0.5,achieved the maturity standards.The results showed that,the bentonite adding reduced total nitrogen loss and accelerated organic carbon mineral for more than 15.27%-19.71%,the percentages of DTPA extractable heavy metal?Cu,Zn,Pb,Cd?in compost piles were decreased,which improved the heavy metal passivation.Adding bentonite also reduced the content of E1 in the compost.At the end of the compost,the content of E1 in 5% bentonite treatment was only 28.27 ?g·kg-1,reduced the environmental risk of estrogen.The study found that adding less than 5% bentonite to sludge compost was more suitable.?3?The p H of alkali solids amendment compost and CK treatment decreased at the beginning and then gradually increased before reached values of 6.78-7.33.The straw biochar amendment reduced the salinity of the compost with final products EC was just 623.00 ?S·cm-1,lower than other reatments.Fly ash and lime amendments had slight inhibitory effect on plant germination.Compared to the beginning stage of compost,the alkali solids amendment could increase the total nitrogen content.The addition of straw and hardwood biochar could reduce the ammonia loss at the beginning,while the fly ash and lime amendments would result in ammonia loss in the beginning stage.Straw and hardwood biochar amendment would increase NH4+-N in the beginning stage.Despite the composting variation,the contents of nitrate increased and reach 765.3 mg·kg-1,723.4 mg·kg-1 in straw and hardwood biochar final products.?4?The results of brassica pot experiment with alkali solids amendment composts showed that: Compost addition increased the soil organic carbon content,as well as soil N,P,and K contents.Applying compost products significantly improved the brassica growth and improved chlorophyll content,and straw biochar amendment compost worked best.Compared with the non-amended compost,the alkali solids amendment slightly reduced the Cu and Zn micronutrients accumulation,while the fertile potentials were acceptable.In conclusion,straw biochar was more suitable as compost amendment,and the related compost products had great potential on infertile soil amelioration. |
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