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by B .G . Lotterm oser and G . M orteani Sew age sludges:T oxic substances,fertilizers,or secondary m etal resources?

toxic substances that require dum ping in special w aste repositories but also as high-quality fertilizers or very interesting secondary m etal resources. This paper sum m arizes the environm ental regulations for sew age sludge treatm ent and disposal, and it discusses the potential 称aehgnew tSreelduadt mcgmesnic tae cpncltaruamntisod,ia iaste nq dafs to hivreagYas tnecio cpm r1om)odolutlciult-i sa, ncitois ns tweawild-l of sew age sludges as fertilizers and secondary m etal resources. heavy atid noble m etals. The m ethody_ of Ylw}Qe

Sew age sludge disposal

as Sludge disposal methods include (1) Its,com posting and use m‘ fertilizer on agricultural land, (2) o c e a n dum ping, (3) disposal garbage dum ps and landfi lls, and (4) incineration or pyrolysis and subsequent burial of slags and ashes in suitable w aste repositories.

U se a s fertilizer

Sludges from m unicipal sew age treatm ent w orks, m ainly those from plants that rem ove phosphates from w astew ater, are know n to be very good phosphate fertilizer (Furrer, 1980 , 1981; H dni, 199 1). A considerable am ount of sew age sludges is used as fertilizer on agri- 级 cultural land; in G erm any, this takes 35 percent of the annually accum ulating sludges. For such use, several governm ent authorities pmreoevletlaunltusae,n st sflaorovaimdnsg stah seo f ex rteirxlaipzcetinrosSni vo enof a whgearaisctveuY l tuarnreapdlo snlai.ot nobdrlYe, have set the m axim um acceptable heavy m etal concentrations in sew age sludge, m axim um values for m etals in sludges applied to land, and annual loadings of m etals and total m etal concentrations in sludge-am ended soils (L ester, 1987a). M etals for w hich the m axi- simpoaupcracece,t sc, oanns dceor pvnartietnivoeennt taoifol na p nrodifm m paoraysrsi nigbeloe el coeognsiv.cvi,} rItonetcinmtuse.l声 m um acceptable levels are set include cadm ium , chrom ium , , m ercury, nickel, lead, selenium , and zinc, and in som e countries, m axim um acceptable values have been given as w ell for organic In tro d u ctio n pollutants. In order to defi ne the im portance of the problem , w e should note that w aste production and sew age sludges are not the Sewage sludges are anaerobically digested or aerated end products m ost signifi cant source of heavy m etal soil pollution, but atm os- of w astew ater treatm ent and purifi cation. I hey represent about 10 pheric deposition is. For exam ple, in G erm any, atm ospheric deposi- percent of m unicipal w aste production (Forstner and others, 1991). tion of the elem ent cadm ium is on the order of 90 tons (t) per year, These sludges are know n for their nonbiodegradable and conse- w hereas sew age sludge contributes only 13 t per year (H im i, 199 1). quently persistent, potentially elevated contents of organic pollutants (for exam ple, phenol, polychlorm ated hiphenyls, and phthalates) and of heavy m etals and m etalloids (for exam ple, lead, cadm ium , chro- T able I一 Typ ical hea vy m etal contents in sew age sludge m ium , copper, nickel, zinc, m ercury , , and selenium ) (Lester, [U nits are in m g/kg of dry m atter;一,not significant] 1987a, b) (table I). R elease of part ia ll y treated, or even untreated, m unicipal w aste- E lem en t U n ite d S tate s G reat Britain' Sw eden' ItalY 2 w aters and sew age sludges into continental and m arine ecosystem s L e ad 1,380 8 2 0 2 8 1 2 10 m ay cause environm entally and politically unacceptable problem s, C ad m ium 7 4 13 2 including the contam ination of w ater supplies, endem ic diseases, C hrom ium 2,031 9 80 8 7 2 62 offensive sm ell, eutrophication of lakes and rivers, and phytotoxicity C opper 1,024 9 7 0 7 9 1 36 0 and zootoxicity, along w ith subsequent possible effects to anim al or N icke l 3 7 1 5 10 1 2 1 4 2 hum an food chains. T he problem is grow ing because of increasing Z inc 3,315 4 ,100 2 ,0 55 1,540 population and industrialization, especially in the less developed 4 c o u n tr ie s M ercury

D epending on the com position of the sew age sludges and on H an i, 199 1 pertinent legislation , these sludges m ay be considered not only as 2 G . M orleani, unpublished data

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T h e m axim um perm issible concentrations for individual heavy Table 2. - M axim um heavy m etal concentrations in sewage sludge m etals in sew age sludges used as fertilizer differ by as m uch as 100 that are considered p erm issible for use as agriculturalf ertilizer percent (see table 2). T his clearly dem onstrates that the behavior of (U nits are in m g/kg of dry m atter;一,not significant. A bbreviations: E .C ., heavy m etals in soils, w eathering profi les, ground-w ater aquifers, European C om m unity] and plants is largely unknow n. Insufficient also is the know ledge ot G G erm any the potential toxicity problem s and bioaccum ulation of heavy m etals E le m e n t E .C . e rm a n y Italy Sweden' that arise in food chains from the application of sew age sludges 1984 ' 1 9 9 2 份0 0 20 ,n 00 750 、 Un to agricultural land. This uncertainty is highlighted by the very L e a d 40 20 1 0 20 1 勺工 different m axim um perm issible heavy m etal concentrations in C ad m ium 20 n 00 760 1 000 sludge-am ended soils, such as those given by G enrian and Italian , C h ro m iu m 一 , 0 0 八 00﹄ 50 20 0 0 、 U regulations (table 3). 八 Copper 1, 1 , , 40 20 2 00 30 勺1 00 N ickel 0 0 勺 工 00 0 l 0 八00 口

O cean dum p ing Z in c 3, ︸. J 3, ‘

For disposal of sew age sludges at sea, several countries have signed M ni, 19 9 1 agreem ents called the O slo C onvention, Paris C onvention, and L on- don C onvention, w hich regulate the dum ping of w aste into m arine T able 3. - M axim um perm issible heavy m etal w aters (Lester, 1987a). H ow ever, the declarations com m only have concentrations in sludge-am ended soils not been m et by the signees, and w astew aters and sludges carrying [U n its a re in m g /k g o f d ry m a tter] pollutants continue to be released into the aquatic environm ent at ocean and shoreline outfalls. 'I hese pollutants subsequently accum u- E le m e n t G erm an y Italy late in sedim ents and m arine organism s. 气0 L e a d 10 0 ︸ Q uantitative estim ates for heavy m e ta l accum ulations in w aste- 1 C ad m iu m 1 . 5 w aters have been perform ed for global, and for som e local, m etal 0 -伟 、 J C h rom ium ~ releases to the environm ent. The ocean outfall system s for the south- 60 、﹄0 ︶ em C alifornian coast in the U nited States represent an extrem e C opper 50 ,0 N ick el J exam ple for the w aste of heavy m etals into the hydrosphere. There, ,0 M ercury 1. the com bined annual discharge has been estim ated at 1,022 t of zinc, 月 ~0 卫 勺 539 t of chrom ium , 402 t of copper, 182 t of nickel, 165 t of lead, 22 Z in c 2。001 二 t of cadm ium , and 20 t of (G allow ay, 1979). Sim ilar ocean outfall system s and associated m etal releases are present in other parts of the w orld, as, for exam ple, in Sydney, A ustralia. G lobal m etal iRiections into the oceans and atm osphere from m unicipal Sludges as secondary m etal resources sew age have been estim ated to be 3,000 t of cadm ium , 55,000 t of chrom ium , 42,000 t of copper. 15,000 t of lead, 440,000 t of iron, 7,400 t of m anganese, 17,000 t of nickel, 2,300 t of silver, and B ecause of the above-listed environmental concerns and the possi- 100,000 t of zinc each year (G allow ay , 1979; N riagu and Pacyna, ble bioaccum ulation of pollutants in food chains, sew age sludges are 1988). regarded m ostly as w aste products. H ow ever, sew age sludges show not only the high contents of heavy m etals m entioned above, but they also possess im portant noble m etal concentrations ( and plati- L a n d fi lls noids) in m ost of the exam ined cases (com pare Furr and others, 1976; M um m a and others, 1983 , 1984, 1988; L otterm oser, 1993). In A s a result of the decreasing acceptance of the use of sew age sludges particular, the gold contents of som e sew age sludges are sim ilar to, in agriculture, an increasing percentage of the sludges w ill be depos- ited in urban solid w aste landfills or in "m onolandfi lls," that is, or even higher than, those of geologic ore deposits that are m ined for gold. landfi lls reserved entirely for sew age sludges. A landfill containing only sew age sludges represents a less com plicated system than a m unicipal solid w aste landfill, w hich generally holds a range of H eavy m etals w aste products (L ichtensteiger and others, 1987; F6rstner and others, 199 1). H ow ever, pollution cases associated w ith landfills have re- T he total heavy m etal content of sew age sludges is about 0 . 1 to I suited in negative publicity, and the developm ent of future w aste w eight percent on a dry w eight basis. Individual heavy m etal con- disposal sites has becom e a m ajor public issue. tents are highly variable; how ever, zinc, lead, chrom ium , and copper are generally present in higher concentrations than are nickel, cad- In c in era tio n m ium , and m ercury (table 1). H eavy m etals appear in a v a ri ety of household products, such as Incineration and pyrolysis of sew age sludges result in signifi cant cleaners, cosm etics, sham poos, and toothpastes, all products that are reductions in volum e, and the m ain residues ot incineration or pyrol- disposed of dow n the drain. H um an excreta, industrial efl uents, ysis of sew age sludges are the slags or the pyrolysis "peat." In both road-runoff w ater carrying traffic pollutants, rainw ater. drinking w a- cases, heavy m etals are highly im m obile. so the slags are w ell suited ter, from w ater-supply piping system s, and ground w ater for disposal in norm al landfills (F6rstner and others, 199 1), or they infiltrating into sew age piping all contribute to the heavy m etal can be used as road-building m aterial (V ogg, 199 1). H ow ever, a contents in w astew aters and sew age sludges. The concentration of problem is posed by the fly ashes, w hich contain easily leachable heavy m etals in sludges varies according to the type of w astew ater heavy m etals and also dioxins and furanes that are produced by treatm ent, the presence of specific m etal- processing industries in the reactions at tem peratures betw een 250 T and 450 T (V ogg, 199 1). area, the lifestyle ot the population, the road-runof contam ination, Such ashes require disposal in special w aste repositories. and the state ot the drinking w ater supply system s.

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Table 4. - R ange of noble m etal conten ts of m unicip al sewage Ir sludges in the U nited States and the F ederal R ep ublic of 05 G erm any [U nits are in m g/kg of dry m atter; num bers in parentheses show num bers of Rh sam ples. D ata w ere taken from F urr and others (1976), M um m a and others (198 3 , 19 84 , 19 88 ), a nd L o tterm oser (19 93 )] Ru U S A G erm an y Pd M in im u m M a x im u m M in im u m M a x im u m

0 00 2 90 了 0 71 一 6 0 0 ‘ 2 6、 八 ‘ 八 、 气 G o ld 0 .2 8 ︸ :

0~ 74 ‘ ‘ 1 1、 1 0 7 了 ,6、 勺 且 勺 . Pt P latinu m < .0 1 几 1 伪勺 ‘ 20 f 4 41 4 7 O ‘ 2 6、 ‘、 U P a lla d iu m ︶ 0 4 可 0气 7 05 f 4 j , C 了 1 ,、 斗! J 、, ︺ , 吸 户 AU R u th e n iu m < 0 1 . 00 勺 70 ‘ 勺 1 气 ︸ 1 , 八 、 .! 、 、 f 、, 1 上 ︶ 1 R h o d iu m ︶ ︶ < .O l 母 ︸ ︶ 0了 今 18 f 且‘ 气、 0 卜一 J 1 勺 n 、 . 胜J1 O sm iu m . ︺ < 0 1 : ︸ 、 1 0气 46 ‘ 1 ︸1 0 飞 f 1 ,、 、 、 0 , 2 3 4 5 Irid iu m 甘 1 J < .O l ︶ ︶ P P M Possible sources of noble m etals in sew age sludges include F igure L - A verage noble m etal contents of m unicipal sewage industrial discharges (for exam ple, dental surgeries, jew elry indus- sludges. D ata refer to dried sew age sludge m atter and w ere taken try), dom estic additions (for exam ple, abrasion of jew elry). autom o- 户om F arr and others (1976), M um m a and others (1983, 1984, 1988), and L otterm oser (1993). A bbreviations: Ir, ; O s, bile em ission control system s (platinoid-bearing catalysts), and to a osm ium ; R h, ; R u, ; P d, ; Pt, plati- lesser degree, background concentrations w ithin dom estic w ater sup- num ; A u, gold; pp m , parts per m illion. plies, surface-runoff w ater, sew er infiltration w ater, and corrosion of w ater pipes (L otterm oser. 1993). H um an excreta have low gold and contents, and they account to an insignificant degree (ap- H eavy m etals w ithin w astew aters are fo u nd as dissolved, colloi- proxim ately 0.0 1 percent) for high noble m etal values in sew age dal, and solid species. Partitioning of dissolved m etals onto solid sludges (L otterm oser, 1993). particles in m unicipal sew ers, especially during w astew ater treat- m ent, takes place by a num ber ot chem ical and biochem ical m echa- T ransport ot these m eta ls w ithin sew er system s possibly takes nism s, including binding to extracellular polym ers; active m etabolic place as solid particles (from industrial sources and dental surgeries), intracellular uptake of soluble m etals by bacteria; absorption by as absorbed elem ents on suspended particulate m atter, as colloids, bacteria] cells, organic particles, and clays; and form ation ot insolu- and as dissolved organic and inorganic com plexes. M ost of the gold ble hydroxides, carbonates, phosphates, sulfates, and sulfides (see in m echanically treated w astew aters appears to be associated w ith C herem isinoft, 1989). Subsequent physical entrapm ent of the heavy m icrom eter-sized suspended particles, and to a lesser degree, the m etal precipitate m ay take place in the biofloc of w astew ater treat- gold is present as a dissolved species (K im and others, 1982). m ent plants. Furr and others (1976) proposed that the elevated gold co n t e nt of the sew age sludges of San Francisco , C alifornia. U SA (7 ppm A u), is a result of gold-enriched w aters from the w atershed area of N ob le m eta ls the city. H ow ever, natural w aters are capable of transporting only very low concentrations of noble m etals, and hence, the gold and Sew age sludges com m only possess high noble m etal contents, in- platinoid enrichm ent of sew age sludges cannot be due sim ply to gold- eluding gold and palladium values w ithin the parts per m illion (ppm ) and platinoid-enriched natural w aters. range (table 4). Som e exceptionally high precious m etal concentra- Precipitation caused by m icrobiol o g ic al activity, reactions w ith tions also have been reported for individual sew age sludges (for organic m atter, decreases in the ligand concentration (sulfur), and exam ple, 56 ppm of gold, Lotterm oser. 1993). Low er concentrations absorption onto sulfides and organic m aterial are likely to be respon- generally have been detected for platinum , ruthenium , rhodium , sible for the rapid and efficient concentration of gold and platm oids osm ium , and iridium (table 4, fig. I). onto organic sew age particles in m unicipal w astew ater system s. T he The highest noble m etal contents ha v e been determ ined in slud- precipitation and enrichm ent processes in the sew ers m ust take place ges accum ulating in cities that have a pronounced jew elry industry. rapidly , as w astew aters generally need only a few hours to reach the E levated noble m etal values also can be expected in sludges produced treatm ent w orks. Sim ilar to the genesis of hydrotherm al gold depos- in localities of recent and ancient noble m ining activities (for exam - its, the destabilization at gold and platm oid com plexes and colloids ple, B enchgo and B allarat in A ustralia). A ll sew age sludges possess from large w astew ater volum es having low contents at the noble higher palladium than platinum values. T he palladium to platinum m etals (parts per thousand to parts per billion levels) could be ratio in sludges in the U nited States is about I I .and in G erm an ones, responsible for the accum ulation at relatively high noble m etal con- it is 4 .5 (fig. 1). T he crustal palladium to platinum ratio is only 1.5. centrations (parts per billion to parts per m illion levels) in the solid T his strong palladium enrichm ent is likely the result of platinoid m atter at sew age sludges. differentiation during transport in m unicipal sew er system s and the Q uantitative estim ates a t gold , platinum , and palladium m asses subsequent preferential deposition of palladium onto organic-rich accum ulating in sludges of the industrialized countries have been m aterial, a feature that com m only is observed in analogous geologic obtained as follow s (see B ow en, 1985): Sludge production has been environm ents. H igh palladium sludges w ill get particular econom ic estim ated at 180 gram s of dry m atter per person per day. It w e interest if the palladium -based exhaust catalysts developed by the assum e a w orld population of 5 billion, of w hich 25 percent is Japanese N ational Institute for R esources and Environm ent prove to industrialized and has m unicipal sew er system s and sew age treatm ent be successful (A nonym ous, 1992). w orks, the production of dry sludge am ounts to approxim ately 82

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m illion t per a n n um (B ow en, 1985). M ean noble m etal contents have In anaerobically digested sew age sludges, m ost base m etals been calculated from published analyses as 1.85 ppm gold, 0. 13 ppm exist in the reduced and insoluble sulfide form . B acterial leaching platinum , and 3.03 ppm palladium . T hese estim ates likely are too causes ox id ation of th e in so lu b le m etal sulfi d es to th e solub le m e tal high because of the lim ited num ber of analyses (gold, 113 analyses; sulfates. Thus, bacterial leaching has been used to extract m etal from platinum , 4 1 analyses: and palladium , 70 analyses; Furr and others, anaerobically digested sludges (for exam ple, see T yagi and C ouil- 1976; M um m a and others, 1983, 1984 , 1988; Lotterm oser, 1993). lard , 1987; T yagi and others, 1988). C urrently, bacterial leaching is Thus, for conservative estim ates, the m ean contents have been as- used to extract copper and uranium from low -grade ores in industrial surned to be 1.25 ppm gold , 0 .10 ppm platinum , and 1.00 pprn heap, dum p , and in-place leaching processes. T he m ajor advantage palladium . Such average noble m etal contents w ould im ply that of bacterial leaching over acid extraction is that good m etal rem oval approxim ately 100 t of gold, 8 t of platinum , and 80 t of palladium can be achieved along w ith a low requirem ent for acid (T yagi and are accum ulating in sew age sludges each year. In com parison, the C ouillard , 1987; Tyagi and others, 1988). Sim ilarly, the requirem ent annual global m etal production from geologic ores am ounts to m ore for lim e to neutralize the sludges is reduced. In addition, the treated than 1,653 t of gold , 100 t of platinum , and 100 t of palladium sludges are easy to fi lter, the sludge nutrients are not dim inished, (M urray, 1990 ; B achm ann, 1990). is not released , and the decontam inated sludges produce less odor (T yagi and C ouillard, 1987 ; T yagi and others, M etal recovery from sew age slu dges 1988). Th e e xtraction of noble m etals from sew age sludges is possible M etals of geologic ores are m ined , extracted, and used for industrial through the use of solutions (com pare M arkels, 1977; products, w hereas m etals in sew age are w asted, dum ped on land or at K rofchak , 1979; and W hitew ay, 1986). A C anadian m ining com pany sea, or even released to the environm ent. R ecycling of m etals con- has been involved in the recovery of gold from sew age-sludge ashes serves prim ary geologic resources, and in som e cases including of the city of Toronto by using cya m d e-ext raction techniques (W hite- sew age sludges. it w ould avoid the uncontrolled release of m etals w ay , 1986). T he effectivity, that is, the extraction rate of hydrom et- into the environm ent. M etals can be, and are, recycled. and this allurgical techniques, is dependent on the reaction tim e, tem perature, secondary industry is of increasing im portance in the developed leaching agent concentration , and pH conditions. 'Ihe possible lixiv- c o u n tr ie s . iation agents for gold are cyanide , thiourea, thiosulfate, polysulfide, A no b le m etal ore that requires no m ine, no explosives, no , or organic brom ine com plexes. Som e of these agents are crushing, and no trucking, that averages values of parts per m illion of not selective and also form com plexes w ith sulfides and other m etals- gold and palladium , w hose annual w orldw ide production am ounts to 'Ihis results in high reagent consum ption and low recoveries. In approxim ately 100 t of gold and 80 t of palladium , and w hose addition, m ajor health and environm ental problem s are associated production is secured as long as the hum an race exists. this represents w ith the cyanide and organic brom ine processes. an "attrac tive o re. , N o satisfying process seem s to exist today fo r th e extraction of T he extraction o f n oble m etals from sludges can be justifi ed as heavy and (or) noble m etals. T herefore, m ajor research efforts are an environm entally acceptable process, but the econom ic potential necessary一and w ill be w orthw hile一for achieving the extraction of for the developm ent of a viable extraction m ethod also is consider- m etals from sew age sludges. able. The disposal of I t of sew age sludge that has m etal contents above land- application lim its (sludge that cannot be used for agricul- rural purposes) costs at the m om ent in G erm any about D M 250-500- T he prices for dum ping are supposed to increase at a rate of D M 25-50 each year. In contrast, I t of w aste to be treated by com posting costs only D M 30. T hus, the extraction of m etals from C o n c lu sio n s sew age sludges w ould be repaid not only by the value of the m etal but also by the costs that w ould be saved for the disposal of the sludges in w aste repositories. In addition. decontam inated sludges M unicipal wastewaters and sewage sludges contain large amounts having reduced pollutant loads could be disposed of as fertilizer on of heavy and noble m etals. H ow ever, none of these m etals are being agricultural land , and the existing and potential environm ental prob- extracted now from the sludges, and m etals continue to be released lem s could be addressed before they cause toxicity sym ptom s in into the environm ent or literally are w asted in garbage dum ps or plants, anim als, and hum ans. incinerated-ash repositories. O ur "efl uent" societies cannot afford to Several m ethods have be e n u nder investigation for the rem oval w aste raw m aterials, and sew age sludge should not be regarded as of m etal and phosphorus from sew age sludges and incinerated ashes w aste but as a secondary resource for m etals and nutrients for plant (for exam ple, see Scott and H orlings, 1975; O liver and C arey, 1976; g row th . M arkels, 1977 ; K rofchak, 1979; Tyagi and C ouillard, 1987; T yagi Inv e st ig ations by geoscientists could add significantly to the and others, 1988). T hese m ethods include hydrom etallurgical extrac- know ledge on the sources, transport, deposition, concentration, and tion and bacterial leaching. H ow ever, one should rem em ber that the speciation of heavy and noble m etals in m unicipal w astew ater sys- current m etal-extraction techniques do not reduce the concentrations tem s and sew age sludges. O re deposit geologists are confronted by of organic pollutants. A reduction in the organic pollutant loads m ay challenging research opportunities. For exam ple, anthropogenic no- be achieved only by vigorous control of the sources of industrial ble m etal deposits are being form ed now in areas of ocean-outfall efl uents. system s, such as that of A thens, G reece. and these m etal accum ula- B ase m e tals can be rem oved from sew age sludges by acidifying tions m ay be analogous to the ancient black-shale noble m etal the sludges by the use of m ineral acids. H ow ever, acidification is deposits. H ow ever, the noble m etal sources, transport ligands, and associated w ith the consum ption of large am ounts of acid. and at the precipitation and enrichm ent m echanism s that are responsible for the end of the treatm ent, a large am ount of lim e is needed in order to high values in sew age sludges rem ain largely speculative; the posi- raise the pH of the sludge to neutral. A lthough good m etal rem oval tions of noble m etals in the sludges are still unknow n; and the reasons can be achieved in som e cases. the econom ical and operational for the pronounced differences in platinoid distribution in sludges constraints have m ade the practical application of these m ethods from the U nited States and G erm any have yet to be found, true u n a ttra c tiv e . challenges for the future.

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R e f er en c e s O liver, B .G ., and Carey, J.H ., 1976, A cid solubilization of sew age sludge and ash constituents for possible recovery: W ater Research, v. 10, no A nonym ous, 1992, Platin: Erzm etall, v. 45, no. 11, p. 556. 12, p. 1077-1081. Bachm ann, H .-G ,1990, Precious m etals in and for new technologies, in Scott, D .S., and H orlings, H ,1975, R em oval of phosphates and m etals from K iIrsten, M ., ed., Raw m aterials for new technologies, International sew age sludges: Environm ental Science and Technology, v. 9, no. 9, p. 84 9 - 8 5 5 . Sym posium , 5th, H annover, G erm any, 1988, Proceedings: Stuttgart, E. Tyagi, R .D ., and Couillard, D ., 1987, Bacterial leaching of m etals from Schweizerbart'sche V erlagsbuchhandlung, p. 61-70. digested sew age sludge: Process Biochem istry, v. 22, no. 4, p. 114-117. Bow en, H .J.M ., 1985, The cycles of copper, silver and gold, in Hutzinger, Tyagi, R .D ., Couillard, D ., and Tran, F .T ., 1988, H eavy m etals rem oval 0 ., ed ,The natural environm ent and the biogeochem ical cycles, in the from anaerobically digested sludge by chem ical and m icrobiological collection The handbook of environm ental chem istry: B erlin, Springer- m ethods: Environm ental Pollution, v. 50, no. 4, p. 295-316. Verlag, v. 1, part D , p. 1-27. V ogg, H ., 1991, A bfallverbrennung- Fakten und Perspektiven: D e A rbeitge- Cherem isinciff, P.N ., ed., 1989, W astew ater treatm ent technology, volum e 3 her, v. 22, p. 870-873. of Encyclopedia of environm ental control technology: H ouston, Texas, W hitew ay, P., 1986, Lasir to recover gold from Toronto's sew age: The U SA , G ulf Publishing C om pany, 684 p. N orthern M iner M agazine, January, p. 1一 El Fbrstner, U ., Colom bi, C ., and Kistler, R ., 1991, D um ping of w astes, in M erian, E ,ed., M etals and their com pounds in the environm ent: W ein- heim , V CH V erlagsgeselIschaft, p. 334-355 D r. B .G . L otterm oser, born in 1961, Furr, A .K ., Lawrence, A .W ., Tong, S.S.C ., G randolfo, M .C ., H ofstader, studied geology in G erm any and R .A ., Bache, C .A ., G uterm ann, W .H ., and Lisk, D .J ,1976, M ultiele- A ustralia. H e w orked as an exp lora- m ent and chlorinated hydrocarbon analysis of m unicipal sew age sludges tion geologist/consulling m ineralogist ofA m erican cities: Environm ental Science and Technology, v. 10, no. 7, in the m ining industry, p ublished over p. 683一 87 . 25 scientific p ap ers on m ineralogy, Furrer, O .J., 1980 , L andw irtsch aftlicher W ert des K 11irschlarrun s: EA S S em - ore deposit geology, and environ- inar, B asel, Sw itzerland, p. 24-28. m ental geochem istry, and is a post- - 1981, Siedlungskom poste in der Schw eiz- positive und negative doctoralfellow at the School of E arth A spekte: l7th V ortragstagung, Deutsche G esellsehaft ftir Q ualitdtsfors- Sciences, The U niversity of M el- chung, Speyer, G erm any, 26-27 M drz bourne, P arkville 3052, A ustralia. G allow ay, J.N ,1979, A lteration of trace m etal geochem ical cycles due to the m arine discharge of w astew ater: G eochim ica et C osm ochim ica A cta, v. 43, no. 2, p. 207-218. H }ni, H ., 1991, H eavy m etals in sew age sludge and tow n w aste com post, in M erian, E ., ed., M etals and their com pounds in the environm ent: W ein- heim , V C H V erlagsgesellschaft , p. 357-368. D r. G . M orteani born in 1935, stud- K im , J.l., Lux, D ., and Fiedler, 1., 1982, M ultielem ent trace analysis for ied m ining engineering and geology. inorganic species in large-volum e w ater sam ples by m ono-standard H e is currently professor for applied neutron-activation analysis: M ikrochim ica A cta, part 1, p. 137-153. m ineralogy and geochem istry at the K rofchak, D ., 1979, Process for the treatm ent of incinerated sew age sludge Technical U niversity of M anchen ash: European Patent 0,004,778. (G erm any) and author of m ore than Lester, J.N ,ed ,1987a, Sources, analysis, and legislation, volum e I of 150s cientificpapers inp etrology, geo- H eavy m etals in w astew ater and sludge treatm ent processes: B oca Raton, Florida, U SA , CR C Press, 183 p. chem istry, and m ining geology. _ 1987b, Treatm ent and disposal, volum e 2 of H eavy m etals in w aste- w ater and sludge treatm ent processes: B oca R aton, Florida, U SA , CR C Press, 155 p. Lichtensteiger, T ., Brunner, P.H ., and Langm eier, M ., 1987, EW AG -Project N r. 30-681, K lNrschlam m in D eponien: Cost 681-Forschungsprojekt. Lotterm oser, B .G ., 1993, G old and platinoids in m unicipal sew age sludges: Environm ental Science and Technology, subm itted. M arkels, M ., Jr., 1977, Process for the recovery of selected m etal values from w aste w aters: U .S . P atent 4 ,0 33,763 . M um m a, R .O ., R ashid, K .A ., R aupach, D .C ,Shane, B .S., Scarlet-K ranz, J.M ., B ache, C .A ., G utenm ann, W .H ., and Lisk, D .J., 1988, M utagens, toxicants, and other constituents in sm all city sludges in N ew Y ork State: A rchives of Environm ental C ontam ination and Toxicology, v. 17, no. 5, p. 657一63 M um m a, R .0 ,R aupach, D .C ., W aldm an, J.P., H otchkiss, J.H ., G uten- m ann, W .H ., B ache, C .A ., and Lisk, D .J., 1983, A nalytical survey of elem ents and other constituents in central New Y ork State sewage slud- ges: A rchives of Environm ental Contam ination and Toxicology, v. 12, no. 5, p. 581-587. M um m a, R .O ., Raupach, D .C ., W aldm an, J.P ., Tong, S.S.C ., Jacobs, M .L ., B abish , J.G ., H otchkiss, J.H ., W szolek , P .C ., G utenm an , W .H ., Bache, C .A ., and Lisk, D .J., 1984, N ational survey of elem ents and other constituents in m unicipal sew age sludges: Archives of Environm en- tal Contam ination and Toxicology, v. 13, no. 1, p. 75-83 M urray, Stew art, 1990, G old, in M etals and M inerals Annual Review : Lon- don, M ining Journal, p. 9-15. N riaeu . J.0 二and P acvna. J.M .. 1988 . O uantitative assessm ent of w orldw ide

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