The Study Of Adsorption Characteristics Of Pollutants In Saline Wastewater By Constructed Wetland Substrates

The shortage of fresh water resources is one of the extrude problems whichrestricts the social sustainable development of our country.This phenomenon is muchworse in eastern coastal city which quantity of per capita water is less than60%of ourcountry. The directe utilization of sea water is becoming an effective method ofsolving water shortage in coastal cities. However the salinity of saline wastewater ismuch higher, which increases the difficulty of biological treatment. Constructedwetland is a kind of ecological sewage treatment technology, which has a greatremoval efficiency of nitrogen and phosphorus. This article selects4common fillersthat Constructed wetlands packing (furnace slag, clinoptilolite, ceramsite, modifiedclinoptilolite), study the influence of water salinity on the adsorption properties,provide some theoretical basis for the choice of constructed wetlands fillers, the mainresearch conclusions are as follows:(1) In the condition of25℃and neutral influent, Freundlich equation andLangmuir equation both can be used to describe the static adsorption of ammonianitrogen and phosphorus by these four kinds of filers. The increase of pollutantconcentration led to a decline of removal efficiency while the ceramisite had thelowest level of the decline. The saturation adsorption capacity for ammonia nitrogenof slag、clinoptilolite、ceramsite and modified clinoptilolite were0.091mg/g、0.504mg/g、0.230mg/g、0.912mg/g respectively while their descending order wasmodified clinoptilolite> clinoptilolite> ceramsite> slag. The saturation adsorptioncapacity for phosphorus were0.156mg/g、0.058mg/g、0.133mg/g、0.096mg/grespectively while their descending order was slag> ceramsite> modifiedclinoptilolite> clinoptilolite. Ceramsite can be used to treat wastewater with highconcentration of ammonia nitrogen. Slag was suitable for treating sewage with highphosphorus concentration. Clinoptilolite had a great adsorption capacity of ammonianitrogen and a bad adsorption capacity of phosphorus.The action of modify canimprove the adsorption capacity of ammonia nitrogen to1.8times of clinoptilolite and 10times of slag.(2) The increase of salinity will cause decline in the efficiency on the filleradsorption, the main reason is the disruption of K+, Ca2+plasma in seawater, haydite’sadsorption of ammonia nitrogen and total phosphorus efficiency are greatlyinfluenced by salinity, the influence to furnace slag, clinoptilolite, modifiedclinoptilolite adsorption efficiency of total phosphorus is less, the adsorption ofammonia nitrogen are greatly influenced by salinity, but when salinity is lower than1.5%, all three’s removal rate of ammonia nitrogen drop less than50%.(3) In the dynamic adsorption experiment, slag and clinoptilolite adsorption ofammonia nitrogen, total phosphorus’s efficiency tend to the same with the change ofthe experimental conditions, with the extension of hydraulic retention time theremoval rate increases higher and reduce with the increase of concentration ofpollutants; The dynamic adsorption equilibrium time of two kinds of filler forammonia nitrogen are longer than those of the total phosphorus adsorptionequilibrium time, the clinoptilolite has a higher efficiency on the dynamic adsorptionof ammonia nitrogen, and slag for phosphorus adsorption effect is better; Slag andclinoptilolite adsorption effect of nitrate nitrogen and COD is poor, the removal rate islow, these two pollutants’removal cannot mainly rely on the adsorption effect of fillerin saline wastewater.(4) The modified clinoptilolite and ceramsite in the condition of neutral, roomtemperature and hydraulic retention time of24h, dynamic saturated adsorptionquantity of ammonia nitrogen were0.594mg/g and0.178mg/g, dynamic saturatedadsorption quantity of total phosphorus were4.698×10-3mg/g and7.560×10-3mg/g,the water flow state of dynamic adsorption experiments is more close to thepracticalengineering, so filler’s dynamic saturated adsorption quantity has more referencevalue. Modified clinoptilolite of ammonia nitrogen dynamic and static saturatedadsorption quantity were both bigger than ceramsite ceramsite dynamic and staticsaturated adsorption quantity of total phosphorus were both bigger than themodifiedclinoptilolite.