垃圾滲濾液廢水站設計研究-資料下載頁

　　

【正文】 29 / 43附錄 2：外文原文Design of leachate water stationingJournal of Hazardous Materials Stripping/ ?occulation /membrane bioreactor/reverse osmosis treatment of municipal land?ll leachate1． IntroductionLeachate is a high strength waste water formed as a result of percolation of rainwater and moisture through waste in land?lls ．During the formation of leachate， anic and in anic pounds are transferred from waste to the liquid medium and pose a hazard to the receiving water bodies． Production of land?ll leachate begins with introducing moistured waste into disposal area and continues for several decades following the land?ll closure．Leachate contains high anic matter and ammonium nitrogen and its position depends upon the land?ll age， the quality and quantity of waste，biological and chemical processes that took place during disposal， rainfall density， and water percolation rate through the waste in the land?ll． Depending upon what was placed in the land?ll， leachate may contain many types of contaminants， and if not removed by treatment， these contaminants may be toxic to life or simply alter the ecology of receiving streams． Leachate should be treated before reaching surface water or ground water bodies， because it can accelerate algae growth due to its high nutrient content， deplete dissolved oxygen in the streams， and cause toxic effects in the surrounding water life． Since the position of a leachate consists of a wide range of contaminants， it cannot be easily treated by conventional methods． Therefore， a number of scientists around the world have intensively focused on the bination of biological and physicochemical treatment systems for effective leachate treatment． The physical and chemical treatment processes include chemical oxidation， coagulation–?occulation， chemical precipitation， activated carbon absorption， ozonation， and pressuredriven membrane processes． Ozonation and reverse osmosis could be considered following an effective biological treatment to reach a better ef?uent quality． In general， physicochemical units are not enough to remove anics from leachate． The disadvantage of treating leachate with coagulation and precipitation process is that excess sludge is produced after the treatment application， which is dif?cult to manage． On the other hand， biological treatment alone does not achieve high removal ef?ciency due to inhibition effect of some contaminants such as ammonium and heavy metals． For example， as physicochemical treatment ensures the removal of metals and partially ammonium， biological treatment is necessary for the stabilization and degradation of anic matter， and also for the nutrient removal． Among advanced biological treatment processes， membrane bioreactor (MBR) is the most important process ，which consists of a membrane module and a bioreactor containing generally activated sludge with high mixed liquor suspended solids (MLSS) of greaterthan10，000mg/l． The application of membrane bioreactor as a main treatment after physicochemical application seems to be promising due to the expected high ef?uent quality． However， ozonation and reverse osmosis could be used as a posttreatment following biological treatment to remove the residual anic matters． This study presents an effective treatment con?guration for land?ll leachate． The objectives of this study are to investigate：(1) the performance of coagulation as a pretreatment for leachate， (2) the potential of ammonium stripping for ammonium removal under different conditions， (3) the performance of membranebioreactor placed after the coagulation and ammonium stripping， (4) the effect of solid retention time on the aerobic/anoxic MBR (Aer/An MBR) performance， (5) the relationship between viability and inert COD in Aer/An MBR， and (6) the ?nal ef?uent quality if reverse osmosis is used as an optional posttreatment for the removal of residual anic matter after aerobic/anoxic MBR． 2． Mini review on treatment trials Unfortunately， most of the land?lls in the world do not have an appropriate leachate treatment system． Although some treatment options are available， treatment alternatives for leachate are very limited because they are not usually designed by considering the leachate characteristics． Hence， it is necessary to develop leachate treatment systems with reduced footprint and effective ef?ciency． High ammonium and phosphorus de?ciency in young leachate constrain the biological treatment applications such as nitri?cation denitri?cation processes following phosphorus addition．Some researchers received nitri?cation ef?ciency higher than95% for leachates containing high ammonium by using some expensive biological methods． It has been realized that biodegredation mechanism depends upon the age and origin of the land?ll， and the type and operation of the treatment system． In general， almost all treatment schemes used for land?ll leachate consist of a bination of physicochemical and biological treatment units． In order to asses the performance of biological treatment； COD ef?ciencies have generally been evaluated according to the intensity of leachate， number of treatment steps， hydraulic retention time (HRT)， and anic loading rate． AlvarezVazquez et al． estimated that the percentages of treatment systems used for leachate treatment were 72% biological processes， 11% ?occulation/coagulation， 5% ?ltration， 4% air stripping， 4% chemical oxidation， 2% activated carbon， and 2% ionexchange．2．1． Biological treatment for land?ll leachate Biological processes are very effective when applied to young leachates， but their ef?ciency decreases with an increased leachate age． In particular， conventional biological systems cannot signi?cantly treat old leachates， which contain contaminants resistant to biodegradation． Furthermore， old leachates have inhibition effect on