| The hygiene landfills have the advantage of low investment, low processing cost, land an make use of after garbage stability.Currently and Long period, it is the main method of the city life garbage processing at home and abroad advantage. Treatment of the landfill leachate is the key link of hyginene landfill.Because of the high concentration of color, CODcr and ammonia-nitrogen ,the treatment of the landfill leachate is difficult and the result is not ideal.Separate leachate treatment can lead to the satisfaction to the national emission standard but bring about high cost, which is not suitable for economic conditions of Kunming. With expansion of urban scale and continuous increase of population, more and more urban refuse is generated. It is imminent to find a treatment way for leachate suitable for local conditions of Kunming. The purpose of this test is to adopt leachate recirculation treatment by making full use of the advantage of Kunming where evaporation capacity is more than precipitation, and there are abundant solar resources. It is proved that the recirculation is the basic way to treat the leachate produced from two waste landfill sites at the east and the west of Kunming.(1) With increase of recirculafion load, the evaporate ratio increases correspondingly. Soil evaporation is even more than evaporation from water surface. It is suggested that recirculation load be 150% of average daily evaporation from water surface of that month. In this way, the maximum evaporation could be reached. (2) The time period when solar radiation is the strongest in Kunming is 10:00-18:00. In this period, the soil evaporation in Kunming occupies 85% of total daily evaporation. Especially during the four hours from 12:00 to 16:00, the evaporation occupies 52% of the daily evaporation. If leachate recirculation is conducted during this period, evaporation could be increased with maximum efficiency. (3) Under certain recirculation load, it is advised to increase times of recirculations and keep soil moisture content always in saturation state so as to improve evaporation. After recirculation have been conducted for four times, however, effect of increasing recirculation times on evaporation becomes weak, which has no obvious effect. In consideration of operation cost and difficulty in management, recirculation frequency shall not exceed 4 times/day. (4) The method of improving evaporation by heating leachate with solar energy is proposed. When the average increased leachate temperature is 31.1℃, the evaporation could be increased by about 30%. (5) When soil moisture content is more than the critical soil moisture content, the ratio of soil evaporation to soil evaporation capacity approximates to 1, i.e. soil evaporation approximates to soil evaporation capacity, which has no bearing on soil moisture content. When soil moisture content is less than the critical moisture content, this ratio shows line relationship with soil moisture content So when moisture percentage of the soil selected for this test reaches 30%, the soil evaporability could be reached. (6) Wind can increase the soil moisture evaporation by about 30% to the maximum extent. However, when soil surface is dry, the effect of wind would become weak obviously. (7) Although the annual relative humidity in Kunming area is 74%, the humidity in the daytime is low. The minimum humidity after noon is only about 30%. Such dry climatic condition is really suitable for evaporation. |
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