The Degradation Of Polyacrylamide In The Sludge And Soil And Its Impact On Ryegrass And Soil Enzyme

Polyacrylamide (PAM) is a linear water soluble polymer which is widely used in oil extraction,water treatment,papermaking,textile and dyeing,and mining fields,etc.By2010the usage amount reached306,900t/a.PAM is mainly used as flocculant of municipal sewage treatment plant.Lots of PAM is added during the process of sludge dehydration so that there is certain amount PAM leftover in the dewatered sludge.It results poor permeability,high hardness after drying,and is not conducive to the subsequent treatment of the sludge. Meanwhile the degradation of PAM is about10%each year in the natural environment,so there will be a lot of PAM residue in the environment, and gradually accumulate to a rapid growth rate, which is bound to cause a series of environmental problems.The paper systematically summarizes the types,characteristics,application status and degradation research progress of PAM,introduces the disposal status and existing problems of sludge.As now the main disposal ways of sludge are direct land-use and land-use after composting.In this paper,the dewatered sludge used for experiment taken aerobic composting is from the municipal sewage plant,observing sludge composting changes in temperature,humidity and pH,measuring changes of PAM content during the sludge composting process and investigating PAM degradation rate simultaneously. The paper studies the different applying proportion of dewatered sludge and composting sludge affect ryegrass physiological indicators which mainly refer to chlorophyll, soluble protein, SOD, MDA and compare the pros and cons of the two utilization ways.PAM is a good soil conditioner.The paper studies low dosage PAM applied to the soil which ryegrass grows in influencing ryegrass physiological indicators and soil enzyme activities.In the end, the conclusions of the experiment are followed:(1) PAM of sludge under natural conditions is very difficult to degrade, only degrading1.3%in43days.The sludge in the composting process due to microbial biodegradation effects and high temperature caused by thermal degradation, so that40.07%of PAM was degraded within43days of composting time.The degradation efficiency much higher than the rate of natural degradation of the environment, which can effectively reduce the hardness of the sludge and improve sludge permeability, to make it more suitable for land use.The degradation of PAM applied in the soil is from1%to1.5%,the degradation rate is lower.(2) The application of dewatered sludge and composted sludge can improve soil fertility and promote ryegrass growth.Comparison the two applications, dewatered sludge’s fertility is higher.As the increase of sludge proportion, the toxic substances will produce certain toxic effects to ryegrass.The severer poison dewatered sludge produces,the more toxic contents it has.(3) The PAM dosage of this experiment is small,as the gradual increase of it,the inhabitation of soil urease is enhanced. PAM applied lifted moisture retention and fertilizer of the soil, thus promote the growth of ryegrass. Applied PAM has no significant influence to soil catalase activity.