(1) The nitrogen, phosphorus and potassium nutrients in the compound fertilizer are greatly reduced. Because the main component in the sludge is soil particles, it is grayish black, mainly a reducing product, which will become light after drying at high temperature. Adding 50%-70% of the compound fertilizer is equivalent to adding 50%-70% of loess, and the nitrogen, phosphorus and potassium nutrients are below 15%.
(2) There is no special microbial activity in this fertilizer. If the pretreatment is improper (such as incomplete drying), some pathogenic bacteria may be brought in.
(3) Sludge is often a carrier of heavy metals, especially cadmium, mercury and lead are several times to several tens of times higher than the allowable content of soil. We have analyzed the so-called organic active fertilizer that is free in the United States. Containing 2.5% nitrogen, containing 0.8% phosphorus pentoxide, but its heavy metal content is more than 3-11 times that of Shanghai Suzhou River bottom sludge. It can be said that this kind of active organic fertilizer sent by some developed countries is actually a sewage disposal measure.
Problems with active compound fertilizer
Active compound fertilizer refers to sludge or garbage as the main component. The so-called activated sludge refers to the sludge deposited in the municipal sewage treatment plant or the sedimentation tank of the sewage disposal device. It contains certain nitrogen, phosphorus and potassium nutrients and organic matter, and has the biological activities of various microorganisms (including pathogenic bacteria). The industry believes that the main problems of this product are:
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