Biological Activity Multilayer Coverage Technology Repair Contaminated Sediments From The Ancient Canal In Yangzhou

With the rapid advance of China’s industrialization and urbanization and rapideconomic and social development, water pollution is becoming more and more serious,the degree of sediment pollution of surface water bodies is also increasing, with thedevelopment of external sources contamination control technology and the continuousimprovement of the effect of governance, internal sources （sediment） pollutionproblem is outstanding.At present, the methods of reducing internal sources contamination release ofsediment have natural attenuation, dredging and capping. Natural attenuation applies toconditions that sources of contamination have been effectively controlled, andcontaminates can be rapidly sedimented and diluted. Dredging is the most expensivetechnique which results in the greatest mass removal from the aquatic environment,and at the same time it only shifts the contamination problem to another place as theremoved sediment has to be dumped elsewhere and thus requires further management.Capping method has received intensive research, which is developed from traditionalthick physical masking layer to thin hypersorber layer, and the thin hypersorbercapping have such main problems:（1） hypersorber costs high;（2） adsorbent efficiencyis not high;（3） uneven coverage and benthic organism promote the release of sedimentcontamination. To this end, group proposed bioactive multilayer capping technology,using biological zeolite and sand as covering materials, repairiing contaminatedsediments through the synergy of biozeolite and sand. Subject to overlying water andsediments of the ancient canal in Yangzhou, make the field monitoring and laboratorysimulation experimental research.The results show that:（1） Eutrophication in the ancient canal in Yangzhou are serious.Both of low DO and low contamination load of overlying water will promote the release of nitrogen,phosphor, iron and manganese from sediments; when DO <5mg L^-1, ammonianitrogen in Yangzhou old canal is release; when DO <1mg L^-1, phosphorus, iron andmanganese from sediments are release, when DO=2⁵mg L^-1, when DO=2⁵mg L^-1, phosphorus and iron contaminant in the overlying water were absorbed intosediments, however, manganese contaminant behaved alternately released into theoverlying water and absorbed into sediments.（2） Biological activity multilayer coverage technology repair sedimentcontamination in Yangzhou ancient canal is feasible, the best combination is thatbiological zeolite lays under river sand. Mechanism is: through the synergy ofbiological zeolite and upper river sand repair the sediment contamination; The mainfunction of the upper river sand is physical cover, and the lower biological zeolite actswith physical, chemical, and biological function together.（3） Biological activity multilayer coverage technology has better removalefficiency not only to the nitrogen contamination in overlying water but also to ironand manganese; In addition, it has certain reduction efficiency to nitrogen andphosphorus and so on in sediments,in short,bioactive multilayer capping technology isa kind of economic and effective technology in repairing contaminated sediments.（4）Under laboratory test conditions(Temperature is22²7℃,DO=1⁴mg L^-1,pH=7⁸), when the upper river sand covered for the strength of10kg m^-2, thebiological zeolite covered strength for2kg m^-2, the removal rate of total nitrogen andnitrate in the overlying water is separately67.59%and79.53%.