Effects Of Utilization Of Municipal Sewage Sludge On Irrigated Desert Soil And Safety Evaluation

Increasing levels of urbanization, the urban population increase caused increasingurban sludge. The treatment and environmental risks of municipal sewage sludge disposalproblem has been widespread concern in today’s society and mankind. City sludge containsa lot of nitrogen, phosphorus, potassium nutrients and other trace elements needed by plants.Municipal sludge in agriculture can not only improve soil nutrients, but also improve soilphysical and chemical properties, it is a very potential organic fertilizer. Heavy metals,toxic compounds and pathogens and other harmful substances in municipal sludge can beabsorbed and enrichment by plant as the sludge into the soil fertilization, then eventuallyharm to human health through the food chain. This paper discussed by pot experiment:(1)the effect on rate of emergence, growth status and yield of different soil sludge mixingratio on wheat;(2) the effect on soil fertility of different soil sludge mixing ratio;(3)theeffect on the levels of trace elements of different soil sludge mixing ratio in soil and safetyevaluation;(4) the effect on heavy metals lead and chromium of different soil sludge mixingratio in soil and safety evaluation;(5) the effect on wheat grains′trace element content ofdifferent soil sludge mixing ratio and safety evaluation;(6) the effect on wheat grains′heavymetals lead and chromium of different soil sludge mixing ratio and safety evaluation;(7) the effect on economic traits and yield of different fertilizer levels of municipal sludgeon wheat by field trials.The main findings are as follows:(1) Different soil sludge mixing ratio have impact on wheat grain germination andgrowth of plant, appropriate sludge fertilizer can promote grain germination and plantgrowth, excessive fertilization will inhibit grain germination and growth of seedlings, urbansludge can the amount of administration. In this experimental study conditions, differentsoil sludge mixing ratio on wheat grain germination and plant survival rate is different, thetest results of3treatment was the highest, the mixing30%of sewage sludge compostingand70%of the soil, the best effect to promote the emergence rate and the wheat growth.(2) Municipal sewage sludge fertilization better than chemical fertilizers on crop yieldsoil. In this experimental study conditions, potting mix fertilizer accounts for70%of thequality have beyond the affordability of the wheat grown, fertilization have inhibition onwheat grain produced. With the increase in the proportion of municipal sewage sludgemixed wheat dry matter accumulation amount is gradually reduced, while mixed municipalsludge ratio exceeds90%of the sample, fertilizer has seriously affected the dry matteraccumulation of wheat shoots; under40%of cases of municipal sludge mixing proportionof the total soil on wheat growth significantly effect the largest; municipal sludge soilmixing ratio exceeds80%of the total, it will seriously inhibit the formation of wheat grain.(3) Urban sewage sludge resource utilization compost to improve soil environment,increase soil nutrients, change soil physical properties and promote the degree ofdecomposition of soil. In this experimental study conditions, with the increase in theproportion of municipal sewage sludge, soil organic matter significantly increased; total nitrogen, total phosphorus, hydrolytic nitrogen, phosphorus and potassium in soil areincreasing obviously; soil pH gradually approaching pH of sludge, have remarkable results;soil total potassium do not change significantly.(4) Effective control of trace elements by national soil classification standard, whenmunicipal sludge mixing ratio exceeds60%, the iron content in soils reached a highstandard; when municipal sludge mixing ratio exceeds20%,soil available copper and zinccontent effectively to achieve a high standard; when potting soil samples have all of thesludge, the manganese content in soils is in the middle of the standard range.(5) With the increase in the proportion of municipal sewage sludge, the total soil ironand manganese amount do not change significantly, the copper and zinc amount isgradually increasing. By comparing soil environmental quality standards (GB15618-1995),the total soil copper and zinc amount is in the secondary standard range, iron andmanganese did not give a corresponding evaluation criteria.(6) Municipal sewage sludge fertilizer affect soil heavy metals lead and chromiumchanges, with the increasing proportion of mixed municipal sludge, soil heavy metals leadand chromium content is increasing, and the results are significantly different. Bycomparing soil environmental quality standards (GB15618-1995), the total soil lead andchromium amount is in the secondary standard range, therefore, under the experimentalconditions studied, all season fertilization treatment is safe, but taking into account thelong-term heavy metal contamination, sludge fertilization should be carefully considered.(7) With the increase in the proportion of municipal sewage sludge mixed, the traceelements iron, copper, zinc, manganese and heavy mental lead, chromium content in wheatgrain are increasing gradually. By comparing soil environmental quality standards(GB15618-1995),when city sludge ratio is more than80%,the copper content in wheatgrain exceed the standard; when city sludge ratio is more than90%,the zinc content in wheatgrain exceed the standard; when city sludge ratio is more than60%,the lead content inwheat grain exceed the standard; when city sludge ratio is more than70%,the chromiumcontent in wheat grain exceed the standard.(8) Field test study proves that municipal sewage sludge fertilizer can promote thegrowth of wheat economic traits of each index, increased fertilizer can promote wheat plantheight, ear length, sterile spike growth, increasing the weight of the wheat grain, reducingpregnant spikelets, grain number and grain weight, increasing grain yield, biological yieldand economic factors of wheat.