TOXIC METALS IN REST AREA WASTEWATER Thesis for the Degree of M. S. MICHIGAN STATE UNIVERSITY JAMES RICHARD BERLOW 1976 IIIIIIIIII II IIIII II III III III I LIBRARY UmVa-sity ABSTRACT TOXIC METALS IN REST AREA wASTEwATER By James Richard Berlow Heavy metals can prevent the safe treatment of waste- waters by land system. Since land treatment offers a cost- effective alternative in treating highway rest area waste- waters, it is necessary to determine whether the heavy metal concentrations in those wastewaters will make land treatment impractical. This paper discusses a study of the cadmium, chromium, nickel, and zinc concentrations in the wastewater at a highway rest area near Coldwater, Michigan. These metal concentrations are compared with those found by other researchers in studies of domestic sewage. The data obtained in this study showed that toxic metals are not present in sufficient concentrations to inter- fere with land treatment of highway rest area wastewaters. In addition, this data suggests that the domestic fraction of municipal flow is similarly acceptable for treatment by land systems. If excessive metal concentrations exist, it is IIIer t industrlI tian-col' James Richard Berlow likely that the domestic wastewater is being contaminated by industrial discharges, stormwater, or leaching from distribu- tion-collection systems. in DGpa TOXIC METALS IN REST AREA WASTENATER By James Richard Berlow A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Civil and Sanitary Engineering T976 Dr. Mack he provi Dr. Davi finement for her port dur ACKNOWLEDGMENTS The author wishes to extend special thanks to Dr. Mackenzie L. Davis for the patience, advice, and support he provided during the research and writing of this paper. Thanks must also go to Dr. Earl Erickson and Dr. David Cornwell for their aid in the production and re- finement of this thesis. To Ms. Sue Smith goes a special note of appreciation for her skill as typist and editor of this manuscript. Finally, I must thank my family for their moral sup- port during my college career. ii IITRODUC La To PI Sc MI RI c. APPENDI APPENDI. APPENDI APPENDI APPENDI REFEREN TABLE OF CONTENTS Page INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . 1 Land Disposal Techniques Toxicity of Heavy Metals Phytotoxicity . WONG-D- Aquatic Toxicity . . . . . . . . . . . . . . l Zinc Toxicity . . . . . . . . . . . . . . . . 16 Cadmium Toxicity . . . . . . . . . . . . . . l9 Nickel Toxicity . . . . . . . . . . . . . . . 2l Chromium Toxicity . . s . . . . . . . . . . . 21 Previous Studies . . . . . . . . . . . . . . . . . 23 Sources . . . . . . . . . . . . . . . . . . . . . 27 Methods . . . . . . . . . . . . . . . . . . . . . 29 Experimental Methods . . . . . . . . . . . . . . . 32 Results . . . . . . . . . . . . . . . . . . . . . 34 Discussion . . . . . . . . . . . . . . . . . . . . 36 Conclusions . . . . . . . . . . . . . . . . . . . 39 APPENDIX A . . . . . . . . . . . . . . . . . . . . . . . 40 APPENDIX B . . . . . . . . . . . . . . . . . . . . . . . 49 APPENDIX C . . . . . . . . . . . . . . . . . . . . . . . 52 APPENDIX D . . . . . . . . . . . . . . . . . . . . . . . 54 APPENDIX E . . . . . . . . . . . . . . . . . . . . . . . 56 REFERENCES . . . . . . . . . . . . . . . . . . . . . . . 61 Table ~43 23 H 22 Table LIST OF TABLES Comparative Characteristics of Irrigation, Infiltration-Percolation, and Overland Flow Systems for Municipal Nastewater Maximum Recommended Concentrations of Trace Metals in Irrigation Waters used Continuously on all Soil . . . . . . . Water Quality Criteria for Freshwater Systems Metal Concentration in Domestic Nastewater in Three Urban Areas Metal Concentrations in East Lansing, Michigan Michigan . . . . . . . . Theoretical Metal Concentration in Rest Area Mastewater Cd, Cr, Ni, and Zn at the Coldwater Rest Area iv Page 14 TS 25 26 35 37 ere I. Metab 2. Rest Se Figure l. 2. LIST OF FIGURES Metabolic Mineral Balance Rest Area Water Flow Schematic Page 30 33 Federal Section designi the act treatme ticable dischar eIImlna been c the ap Eff1C1 SUPDli 98h, I etePS. groUnI PTESQI the S grazj tamin INTRODUCTION The "zero pollution discharge“ provision of the Federal Water Pollution Control Act Amendments (P.L. 92—500 Section lOl(a)(l)) presents a severe challenge to engineers designing wastewater treatment facilities. The timetable of the act requires secondary treatment from all publicly-owned treatment works by l977 and implementation of the best prac- ticable treatment for these sources by 1983. In l985, the discharge of all pollutants to navigable waters is to be eliminated. In order to achieve this goal many alternatives have been considered. One of the more promising methods has been the application of wastewater to land. Its advantages include efficient renovation of water quality, recharge of groundwater supplies, and in many cases, relatively low cost.1 Limiting factors in land application systems are nitro- gen, phosphorous, pathogens, and heavy metals.2’3 These param- eters, if uncontrolled, can result in public health hazards, groundwater contamination, and odor nuisances. Heavy metals present a unique problem. These metals will accumulate in the soil and can eventually present a danger to plants, grazing animals, and indirectly to man through potential con- tamination of the good chain.2 tothat fyent i am quit emicipa flow var Iy patte ficantly Mgh daj wants I Average 1,000 g these f generat to 200 munici‘ SYStem exPEns PoundE prOCe: Cant]! trial heavy The wastewater from highway rest areas is similar to that from municipal systems in some ways and quite dif- ferent in others. The flow characteristics of a rest area are quite variable with time as are municipal flows. while municipal flow ikfllows weekly as well as daily patterns of flow variation, rest areas Show a much more exaggerated week- ly pattern. As could be expected, rest area flow is signi- ficantly lower during midweek than on weekends. However, high daytime flow and low nighttime flow shown at municipal plants does also occur at rest areas to a lesser extent. Average flows in rest areas in Michigan vary from a low of 4 While l,000 gallons per day (gpd) to a high of 50,000 gpd. these flows would correspond to the municipal wastewater generated by 10 to 500 persons respectively, they carrespond to 200 to 25,000 rest area users; Current treatment alternatives include discharge to municipal systems, stabilization lagoons, and land treatment systems. The extreme variability of rest area flows makes efficient treatment by on-site physical-chemical facilities expensive. The wastewater in municipal plants can contain com- pounds not found in rest areas. The wastes from industrial processes, commercial facilities, and stormwater can signifi— cantly change the characteristics of the wastewater. Indus- trial wastes in particular can contain large quantities of heavy metals. purely oi toxi domesti gators. all pur these I haPS er Upon a namic i the Tar total exPens other are of COSts. PIESEn SiteS Derty COSt-e It is apparent from the previous discussion that municipal effluents containing a significant fraction of metal-bearing industrial wastes would be unsuitable for land treatment without extensive industrial pretreatment or total elimination of the industrial fraction of the flow. Concern has been expressed as to whether or not even purely domestic wastewaters might contain dangerous levels 5,6 of toxic metals. Significant levels of heavy metals in domestic wastewaters have been reported by several investi- gators.5’6 If these metal concentrations are representative of all purely domestic wastewaters, then the land treatment of these wastes will become less economically attractive and per- haps environmentally impossible.. This would cast a shadow upon a system which shows great potential for providing eco- nomic and efficient treatment of rest area wastes. Since the land aquisition cost is usually a major portion of the total system cost in land treatment, the availability of in- expensive land can result substantial savings as compared with other types of treatment. Rest areas, by their very nature, are often located in remote areas with relatively low land costs. In addition, median strips lands and unused areas of present rest area property can be converted to land disposal sites at many locations. Utilization of already owned pro- perty for land disposal makes this type of system highly cost-effective. eater d areas " and bar way res the lam irrigat‘ nun pur gen-dema fiished processe applicat‘. qmlity h generatio SISpended distribut' WIISyste WDHde go OIIhMSSy Infiltrati PhISicaI, Suiting fr matrix as betWeen i Land Disposal Techniques There are four basic types of land application waste- water disposal systems which are applicable to highway rest areas - irrigation, infiltration-percolation, overland flow, and barriered landscape water renovation systems (BLNRS). Irrigation system (as applied to the scale of a high- way rest area) involve the application of the wastewater to the land by spraying or surface spreading techniques. This irrigation_water is used to support plant growth which in turn purifies the water by nutrient removal. Removal of oxy- gen-demanding organic materials and suspended solids is accom- plished by a combination of physical, chemical, and biological processes as the water seeps in the soil. Pretreatment before application is usually necessary to control bacteriological quality where the potential for direct human contact or aerosol generation is high. Reductions in insoluble organics and suspended solids may be required to prevent clogging of the distribution system or generation of offensive odors. The soil system should have reasonably good drainage qualities and provide good productivity upon irrigation. Minter operation of this system in cold climates is generally not acceptable.3 Infiltration-percolation involves the utilization of the same physical, chemical, and biological treatment processes re- sulting from the percolation of wastewater through a soil matrix as in the irrigation systems. The primary difference between infiltration-percolation and irrigation is the lack of a vegetation system for nutrient removal. As applied to highway system U fiepage to aPPH dogging reduced soil use prevent this sys draulic tion of able soi cover 51 Physical the Hate used at IIdstewat and grit either b 0logical of Men acceDtab prOVIded The crit highway rest area effluents, the infiltration-percolation system usually involves the discharge of the wastewater to seepage pits. Suspended solids removal is recommended prior to application to prevent clogging of the soil matrix. Such clogging would force the rate of wastewater application to be reduced to prevent ponding and eventual system failure. The soil used for such a system should be highly permeable to prevent excessive land requirements. Winter operation of this system in cold climates is possible but at reduced hy- draulic loading rates.3 I Overland flow treatment systems involve the applica- tion of wastewater to sloped terraces of relatively imperme- able soils. These terraces must support a hardy vegetative cover since renovation of the water is dependent on the physical, chemical, and biological processes which occur as the water flows through the vegetation. If sprinklers are used at the upper end of the system for distribution of the wastewater, pretreatment to prevent clogging by large solids and grit is necessary. Disinfection is sometimes necessary either before or after overland flow treatment if bacteri- ological purification is not sufficient. Minter operation of overland flow systems in cold climates is generally not acceptable. Storage or alternative treatment systems must be provided to handle flows generated during this period.3 The BLNRS is very similar to an irrigation system. The critical difference is the placing of an impermeable layer at a d9; act as a the wate or molaS irrigatl pended S The barr cient re and deni of addit groundwa‘ have a gc ditions II should be condition nut attem closure aI I Provides Sh ties of he and BL‘rIRS Surface ve would be p at a depth of five to seven feet below the soil surface to act as a moisture barrier. This barrier is sloped to direct the water to a supplemental carbon source (such as feed corn or molasses). This system retains all the benefits of the irrigation system with respect to removal of nutrients, sus- pended solids, pathogens, and oxygen-demanding materials. The barrier provides the proper environment for highly effi- cient removal of nitrogen through a biological nitrification and denitrification. This system provides a valuable amount of additional protection against nitrate contamination of groundwaters. The upper layer of soil in this system should have a good permeability to insure maintenance of aerobic con- ditions while the lower layer, ideally but not necessarily, should be of somewhat lesser permeability to provide anaerobic conditions. Minter operation in cold climates is generally not attempted, although it is possible if a temporary en- closure and a sufficient heat source can be provided.7 Table l provides a summary of these four land treatment systems. Should rest area wastewater contain significant quanti- ties of heavy metals, the success of irrigation, overland flow, and BLNRS would be threatened. Severe damage to the essestial surface vegetation could occur and a sterilization of the soil 2,12 would be possible. 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Toxicity of HeavngetalS Zinc, nickel, and chromium are all considered neces- sary micronutrients which are utilized in the metalloenzymes 8’9’10 Cadmium and hexavalent chromium are of most animals. toxic at relatively low concentrations while zinc, nickel, and trivalent chromium must be present in much greater quanti- ties.8’9’]0 The acute human symptom from the ingestion of cadmium and hexavalent chromium (usually as chromate) is severe emesis.8 Chronic diseases usually connected with environmental exposure to these four metals include hyperten- sion, cardiovascular disease, Itai-itai disease, and derma- tiers.” Phytotoxicity The toxicity of heavy metals to plants growing on land treatment systems is dependent on several factors. Soil pH is significant in controlling the toxicity. The toxic 2 By metals are much more available at pH's below 6.5-7.0. maintaining pH control through the addition of lime or magnesium carbonate, the toxic effects of heavy metals are not evident until much higher soil metal concentrations are attained. The following table shows the influence of pH on metal toxicity: Zn Addr I179; l 32 6E l3l 262 aYie bAss Hso af' to chela Proper n ant to lused t Organic inaddit I53 mam toxic mei the heavy T We in d We relat be as fol. N' For Chrom IS RISO S 10 Effect of Zn Added and Soil pH on Zn Content and Yield Reduction of Chard Leaves2 Soil pH Added Zn 6.4 7.2 mg/t b pg Zn/g dry weight l.3l 210 ll6 l2 32.7 754 237 74 65.4 l058(7)a 337(5) 100 13l. 2763(4l) 765(9) l77 262. 2692(95) l678(22) 406(27) aYield reduction in parentheses (%) bAssumed to be in irrigation water The quantity of organic matter present in the soil also affects metal toxicity.2 Organic matter has the ability to chelate heavy metals making them unavailable to plants. Proper management of the organic matter in the soil is impor- tant to insure that chelated metals are not subsequently re- leased through a depletion of this fraction of the soil. Organic matter can also provide cation exchange capacity (C.E.C.) in addition to that supplied by the clay colloids. The C.E.C. is a measure of the soil's ability to bind cations, including toxic metal cations. This capacity reduces the toxicity of the heavy metals to plants.2 The actual toxic metal present also plays an important role in determining the degree of phytotoxicity which will occur. The relative toxicity of nickel, zinc and chromium was found to be as follows:40 .++ + = +++ Nl >> Zn > CrO4 >> Cr For chromium, it is apparent that the form in which it occurs is also significant to its relative toxicity. to heavy basis ITIU5 between 5 Garden VE crops ICC grasses I perennial metal tox I both the has the a of metal ciency Ch I Chlorosis 30d dwarf fhlorosis the first Ieaves, CI Mary damas Systems he t0xic "IEta IeaVeS.2,4 Th and (ham ll The variation between plant species in susceptibility to heavy metal toxicity in general and on an individual metal basis must also be considered. A three to tenfold variation between species to heavy metal toxicity is quite possible.2 Garden vegetables are generally extremely sensitive, farm crops (corn, small grains, soybeans) moderately sensitive, and grasses (fescue, lovegrass, Bermudagrass, orchardgrass, and perennial ryegrass) are extremely tolerant with reSpect to heavy metal toxicity.2 The phosphate content of the soil can be important to both the degree and type of phytotoxicity exhibited. Phosphate has the ability to reduce the dwarfing of plants as a result of metal toxicity, but it also tends to accentuate iron-defi- ciency chlorosis.2’4] The most common symptoms of heavy metal toxicity are chlorosis, necrosis, deformation or discoloration of foliage, and dwarfing of the roots and aerial portions of the plant. Chlorosis resulting from an iron-deficiency is usually one of the first observed symptoms. Even through it occurs in the leaves, Chlorosis is actually thought to be the result of pri- mary damage to the roots.2 The highly metal-sensitive root systems have been found to receive the most severe damage from toxic metals, preventing transport of the metals to the leaves.2’42’43 The symptoms of zinc toxicity are chlorosis, necrosis, and dwarfing. Iron-deficiency Chlorosis is especially evident in Ca have I thresI Hunter at 25 Barnet dSI Ib Iaam. concen‘ nate tI those I ported The vi: marginI 0f cadn Posed t be set aPPIied Chain C “Unter, be ITO” bIeachi * ASSUme Tied. 12 41 in cases of zinc toxicity. Some examples of zinc toxicity 41 have been reported. Millikan found 5 mg/£* to be the toxic threshold causing a deleterious effect on the growth of flax. 43 Hunter and Vergano found dwarfing and chlorosis to be slight * at 25 mg/2 and severe at 100 mg/2* for oats. Gall and Barnette44 found the toxic limit for zinc to corn to vary from 451 lb/acre on acid sandy soil to 1402 lb/acre on neutral clay loam. Cadmium can be very toxic to plants at relatively low concentrations. However, it poses a severe threat to contami- nate the food chain at concentrations significantly lower than those required to produce phytotoxicity. Page, gt_al.45 re- ported that 1.2 mg/e* produced at 50% growth reduction in corn. The visual symptoms were reddish-orange coloration of the leaf margin, chlorosis, and necrosis. IThey also found concentration of cadmium in the leaves of corn, beets, beans, and turnips ex- posed to cadmium. EPA13 has proposed that a limit of 0.01 mg/R be set for cadmium concentration of irrigation waters to be applied continuously to soils in order to protect against food chain contamination. Nickel toxicity in oats was described by Vergano and 42 46 They found the symptoms to Hunter, and Halstead, et a1. be iron-deficiency chlorosis. White longitudinal striping or bleaching of chlorotic leaves, necrosis (possibly the result * O O O Assumed to be concentration in irrigation water, time unspec1- fied. ' - 'let'cwfl ‘ ,4: of a save 5;“- ch. dary T'OO' oats we“ on growtl * 60 mg/2 chIorosi: growth ar t9 5 mg/I C action by toxocity to Cr+3 i to Show t sis}3 H chromium I Growth of exhibited Mtter yfe 30-50 mg C 13 of a severe iron-deficiency), and stunted growth. At 1.0-1.5 mg/t* chlorosis appeared. Following exposure to 2 mg/L* secon- dary root growth was affected. Root growth halted when the oats were exposed to 20 mg/e*. The repressive effect of nickel on growth of oat straw occurred at 28 mg/2* and to oat grain at * . . 41 60 mg/2 . Millikan reported that flax Showed evidence of chlorosis and root growth retardation at 0.5 mg/t*. Aerial growth and necrosis of the plant top occurred after exposure to 5 mg/t*. Chromium toxicity to plants generally is the result of action by the hexavalent chromate form of this metal. This toxocity is generally temporary since cromate is rapidly reduced 3 to Cr+ in soil.2 When chromium toxicity occurs it is reported to show the symptoms of root damage, dwarfing, and some chloro-f sis.43 Hunter and Vergano43 found that in oats 15 mg/2* of chromium resulted in root growth retardation and 25 mg/2* stunted growth of the plant t0ps. Turner and Rust47 found that soybeans exhibited the symptoms of wilting at 5 mg Cr/2*; reduced dry matter yields at 10 mg Cr/e*; and death within three days at 30-60 mg Cr/R*. Table 2 summarizes the recommended values for these metals in irrigation water. Aquatic Toxicity Heavy metal toxicity in aquatic systems has been the subject of much research. The recommendations for fresh water systems are as stated in Table 3. * O O Assumed to be concentration in irrigation water, time unspeCi- fied. 14 TABLE 2.--Maximum Recommended Concentrations of Trace Metals in Irrigation Haters used Continuously on all Soil.13 Metal Concentration (pg/l) Cd 10 Cr .100 Ni 200 Zn 2000 Metal Cd Cd Cd Cd Cr Ni Ni Zn Zn Metal Cd Cd Cd Cd Cr Ni Ni Zn Zn 15 TABLE 3.--Nater Quality Criteria for Freshwater Systems.13 Concentration (pg/1) Conditions 30.0 >100 mg/l Hardness as CaCO3 4.0 <100 mg/l Hardness as CaCO3 3.0 Salmon Spawning Grounds, Hardwater 0.4 Salmon Spawning Grounds, Softwater 50.0 General Aquatic Community 100.0 20 mg/l Hardness as CaCO3 860.0 360 mg/l Hardness as CaCO3 4.0 20 mg/l Hardness as CaCO3 165.0 360 mg/l Hardness as CaCO3 Zinc II at 40 I sponse action: and iml renoveI only h to norI gill s ronmen ness, that t 15 Sig 1n 501 carbon TedUCe Solved relati “955 v 16 Zinc Toxicity The symptoms of acute zinc toxicity to rainbow trout at 40 mg Zn/l were described by Skidmore et al.14 The re- sponse was in the form of three successive and easily timed actions: deep respiratory distress and surfacing, overturn, and immobilization of the gill opercula. When the trout were removed from the toxic environment at the surfacing stage, only half were able to recover. Breathing patterns returned to normal after several days but a complete recovery of the gill structure did not occur. Acute toxicity of zinc is dependent on several envi- ronmental factors. Most influential was the level of hard- ]5 also showed ness, especially the calcium hardness. Lloyd that the salt in which the calcium was input to the system is significant. He found that zinc is markedly less toxic in solutions of calcium chloride than in those of calcium carbonate. Solbe16 suggested that the explanation for the reduced toxicity could be a decreased concentration of dis? solved zinc due to the presence of the hardness cations. The relative toxicity of zinc to rainbow trout for various hard- ness values is stated in the following table: 17 Median Survival Period Versus Hardness and pH for a Zinc Concentration of 7 mg/l16 Hardness pH Median Survival Period (mg/l as CaC03) (minutes) 12 6.6-6.7 220 50 7.0-7.2 300 320 7 6-7.8 470 504 7 7-8.0 660 The experiments shown in the table were not conducted at a uniform pH. However, Mount17 showed in his experiments that zinc toxicity intensified with an increase in pH from six to eight. The reduced toxicity indicated by the above table would appear to show that the effects of the hardness cations were more than sufficient to overcome the increased toxicity due to the pH rise.16 Variation in the zinc toxicity was also found to vary 112 found that certain "coarse" with species. In fish, Bal species such as bream, roach, and perch were four or five times more resistant to zinc toxicity than trout. Lloyd and Herbert19 found that decreases in the dis- solved oxygen content in water elevated the zinc toxicity to fish. They theorized that a diminished dissolved oxygen concentration increases the flow of water over the gills. Since the gills seem to be the site of action of zinc toxicity, this additional flow of water would bring more zinc in contact l5 with the fish in a given period of time. Lloyd also re- ported that water temperature rises resulted in changes in ‘42.. 7 ...o€3..‘r.¥ab. .. 1.: r"! 18 the toxicity of zinc. The threshold value appeared to remain constant but the survival time was reduced more than half af- ter a temperature variation from 12 to 22°C. In contrast to other toxic metals, Pickering and 20 found little variation in median tolerance limits Henderson for zinc with time. The differential between the 24 hour and 96 hour median tolerance limits for fathead minnows and blue- gills was not found to be significant. When the concentration of zinc is not sufficient to produce acute toxicity, significant chronic manifestations in the aquatic community may still occur. One of the more important aspects of chronic zinc toxicity is the accumulation of the metal by aquatic organisms. Lloyd15 reported significant concentrations of zinc in the tissues of rainbow trout exposed to zinc sulphate preceding 21 death. Jensen et al. found cell concentrations of Phaeodactylum tricornutum grown in water containing 10 mg/l of zinc showed a ZOO-fold increase in zinc content in comparison with a con- trol group. Some Atlantic coast hard and soft-shelled clams were found to contain as high as 4100 ppm zinc.22 Another chronic interference of zinc is manifested in reduced reproductive ability of several organisms. Signifi- cant inhibition with the hatching of eggs laid by fathead 23 minnows at a threshold value of 0.18 mg/l. In diatoms the rate of growth during the exponential phase was diminished, and the ultimate population during the stationary phase was lowered.21 19 Chronic toxicity can also occur in the form of avoid- ance reactions. Sprague24 reported strong avoidance reactions by rainbow trout at a threshold value of 5.6 ug Zn/l. This was 1% of the lethal threshold for these fish. The avoidance intensified as the zinc concentration rose to a limiting value at which there was 100% avoidance. No significant variations in the threshold avoidance reaction were noticed due to tem- perature changes or increases in the background zinc concentra- tion of the "clean" water. Cadmium Toxicity The symptoms of acute cadmium toxicity to bass and bluegills have been best described by Cearly and Coleman.25 Loss of muscular control in swimming, muscle spasms, and convulsions were the first manifestations of cadmium poison- ing. These disorders were followed by loss of equilibrium and periodic paralysis. At death the fins were fully spread, the opercula were expanded, and the body was arched laterally be- tween the base of the pectoral fins and the middle of the dorsal fin. These investigators felt that this behavior sug- gested that the vital damage occured in the nervous system. Variation in cadmium toxicity has been attributed to changes in the length of exposure time. In experiments with several types of fish, important differences between the 24 hour and 96 hour median threshold limit for cadmium were ob- 20 tained. However, very little deviation in the guppies, and goldfish was found. 20 Cadmium is a dangerous cumulative poison. Since excretion rates for cadmium are often very low, dilute con- centrations of the metal can accumulate to produce an acute ‘3 Ball] response after a relatively long period of time. has shown that a lethal threshold of 0.01 mg/l to rainbow trout is not discernable until after seven days exposure. It is suggested in the literature that cadmium toxi- city is related to water hardness,13 however, no formal find- ings of such results are available. Descriptions of chronic toxicity of cadmium to aquatic organisms took several forms in the literature. Accumulation of cadmium by fish, as already mentioned, is an important problem. Bass and bluegill exposed to sublethal concentra- tions of 0.85 mg Cd/l showed lS-fold and 210-fold magnifica- tions in cadmium content respectively after two months.25 Subsequently, an equilibrium appeared to be established and further magnification did not occur. In the freshwater pondweed southern naiad, concentra- tion by over lOOO-fold occured in water containing from 0.007 mg/l to 0.83 mg/l cadmium.26 Such biological magnification poses an extreme hazard to the environment of high-level re- leases of cadmium into the food chain. Reproductive interference with the developing embryos 7 The site of the of the fathead minnow occured at 57 ug/l.2 toxicity was the circulatory system. Although the heart was beating there was no circulation of blood. Those fish that survived were inactive and deformed. 21 Brook trout exposed to 25 ug/l cadmium for 24 hours showed damage to their steroid enzyme system. Testiscular vascularization and discoloration were the apparent symptoms of this toxicity.28 Nickel Toxicity The data concerning acute toxicity of nickel to aquatic organisms have provided some insights into toxicity trends. Hardness appears to play an important role. Pickering and Henderson20 have shown that the median lethal concentration for fathead minnows varies from 5 mg/l in soft water (20 mg/l as CaCO3) to 43 mg/l in hard water (360 mg/l as CaC03). The median threshold limit is significantly lower for 96 hours than 24 hours.20 The data for fathead minnows, blue- gills, guppies, and goldfish appear to indicate a time de- pendence for nickel toxicity. I Chromium Toxicity Trivalent chromium acute toxicity has been shown to be highly variable with concentration. In experiments by 20 the 48 hour mortality of bluegills Pickering and Henderson, exposed to a test concentration of 10.41 mg Cr/l was 90%. For two higher concentrations it was only 20%. The authors explained this data as the result of formation of various types of hydrated chromic sulfate, each of a differential toxicity. In addition, water hardness decreased the toxicity of trivalent chromium.20 22 Species sensitivity to potassium dichromate varied from 17.6 mg Cr/l for the fathead minnow to 118 mg Cr/l for the bluegill.20 Hexavalent chromium toxicity as chromate is dependent on the pH of the system and on the form in which it is intro- duced. This can be demonstrated by the ionic equilbria for monochromate and dichromate: 4 2 Thus, one form of chromate does not exist along in solution. 2 CrOZ + 2 II”—‘—=—-> 2 HCrO :uzo; + H 0 When added as a salt, the buffering system created and the resultant pH play an important role in determining the ionic partition which results. Experiments by Trama and Benoit48 have shown the hydro- chromate ion to be significantly more toxic than either diva- lent form of the chromate ion. They point out that this should be expected since monovalent ions would be more readily ab- sorbed by fish tissues than divalent ions. Their theory sug- gests that a greater proportion of the more toxic hydrochro- mates will be formed when the hexavalent chromium enters the aquatic system as dichromate instead of chromate. The result is a 96 hour median threshold limit in soft water of 110 mg Cr/l for dichromate and 170 mg Cr/l for chromate.29’48 Alkalinity and hardness have been shown to signifi- cantly reduce the hexavalent chromium toxicity.48 In addition, 96 hour median threshold limits are considerably lower than 23 20 the 24 hour limits for several freshwater fishes. Acute chromium toxicity has been shown to occur freshwater algae and marine plants and animals by several investigators.‘3 Accumulation of chromium by trout has occured from water containing as little as 0.001 mg/l.30 The uptake of this chromium was passive, i.e., the amount accumulated was a function of the chromium concentration in the water. In studies of the accumulation of toxic metals by trout with 3] found that only chromium showed respect to age, Tong et al. a significant correlative magnification. The fish studied showed an increase from 5.2 ppb at one year to 90 ppb at twelve years of age. The concentration jumped from 11 ppb at 10 years to 90 ppb at age 12 years. Previous Studies In another study of heavy metals in wastewater, Davis and Jacknow5 isolated the industrial, stormwater, and domestic fraction contributions to the flow in three urban areas. The domestic flow data for New York City and Muncie, Indiana, was based on sampling directly from collector sewers. Pittsburgh's domestic flow data was an approximation based on estimated metals contributions from small commercial establishments? who combined flow was less than 10% of the total at the sampling points. No discussion was given with regard to analytical methods or number of samples collected in the Davis and Jacknow paper. The New York City data is based 24 on an extensive survey conducted during July and August 1972 by the New York City Environmental Protection Administration. The Pittsburgh survey was conducted by Environmental Quality Systems Inc. at six sampling sites from January to June 1973. Muncie's domestic wastewater metals study was based on data collected intermittently during August, 1973, by the Muncie Division of Water Quality. The data is presented in Table 4. Two other studies of highway rest area treatment sys- 32,33 tems have been reported. Neither report considered the potential toxicity of the heavy metals in the domestic flow segment of the wastewater. Lindmore32 considered the potential toxicity of zinc compounds entering the treatment system from camper holding tanks and portable toilet tanks used to inhibit microbiological growth in these systems to prevent odors. A check of several stores in the East Lansing, Michigan area in May, 1976, showed that these zinc compounds have now been re- placed by biodegradable organic acids. In a study of the influent heavy metals to the East Lansing Wastewater Treatment Plant by analytical procedures identical to those utilized in this study, Scott34 found con- centrations comparable to those reported by Davis and Jacknow5 ‘earlier in this paper. Those results are summarized in Table 5. It should be noted that the East Lansing wastewater, while primarily domestic, is subject to accidental discharges from the many laboratories at Michigan State University and to stormwater entering combined sewers. 25 TABLE 4.--Metal Concentration in Domestic Wastewater in Three Urban Areas.5 Metal New York City Pittsbur h, Pa Muncie, Ind (pg/1) (HQ/II (u9/1) Cd 19 13 7 Cr 90 22 8 Ni 90 14 24 Zn 250 200 250 26 TABLE 5.--Metal Concentrations in East Lansing, Michigan Wastewater Metal Concentration (pg/1 i l std. dev.) Cd (28 samples) 55 i 5 Cr (21 samples) 63 i 50 Ni (28 samples) 53 1 57 Zn (35 samples) 239 i 119 27 Sources There are three potential sources of heavy metals in domestic wastewater - human excretion, commercial household products, and leaching from piping and fixtures. All of the four heavy metals under consideration are excreted by the human body. While such mechanisms as perspiration and hair growth can carry out heavy metals ab- sorbed by the body, the Significant body processes in terms of direct contribution to water pollution are urination and defecation. A review of the current literature shows that zinc, cadmium, nickel, and chromium are excreted in both urine and feces. Zinc excretion is primarily by way of the feces. Only a small fraction (about 500 ug) of the 10 to 15 mg of zinc in the average daily intake is excreted in the urine. This is usually assumed to be the result of poor absorption 8,11,35 of zinc in the gastro-intestinal tract. Cadmium ab- sorption from oral ingestion is limited as a result of cadmium's emitic properties.8 Once absorbed, cadmium is retained for 8,36 long periods and excretion is quite slow. The average daily excretion in urine is reported to be approximately 1.5 ug, while fecal excretion is about 31 ug.]]’36 The levels of nickel excreted by people exposed to relatively low amounts of environmental nickel is reported to be 258 ug/day in feces and 2.5 ug/day in urine. The relatively small fraction of urinary nickel is attributed to a low rate of absorption of orally ingested nickel.9 28 The primary source of metal intake for man is through the food chain.8’9’10’36 Many foods such as meat, fish, and grains contain significant levels of the metals considered here. Other examples of dietary sources are listed in Appen- dix E. Inhalation of airborne metals is not significant under normal environmental conditions. Cadmium, chromium, nickel, and zinc inhalation usually accounts for less than 10% of the 8,9,10,36 total daily intake. Cigarette smoking is a signifi- cant source of inhaled metals, but it still adds only a small amount when compared to foods and water.8’9’]0’36 Chromium excretion in urine is estimated to be 8.4 ug/day. Absorption rates of less than 1% to a maximum 25% of ‘0 The remaining portion of the oral does have been reported. the chromium in the diet is excreted in feces. This fecal excretion is much larger than the urinary component since the average daily intake of chromium in the diet is reported to be almost 280 pg/day.]0 Most of the chromium ingested orally and almost all of the excreted chromium is in the much less loxic trivalent form. Commercial household products are another potential source of heavy metals. However, since the potential dis- ruptive effect of heavy metals to septic tank systems has become known, manufacturers have switched to other compounds. A survey of a local grocery store showed no products with any significant amount of heavy metals reported on the labels. 29 The dilution factor for any heavy metals from this source would make any contribution to domestic wastewater essentially negli- gible. The contribution of zinc, nickel, cadmium and chromium added to the water by leaching from piping and fixtures is very difficult to estimate. Due to the various compounds which these metals can form, the solubility is difficult to determine. In addition, the concentration of metal available to be leached is also quite variable. For rest areas it will be assumed that this contribution is negligible due to the short contact time possible in this relatively small piping system. Also, at the pH of rest area wastewater (generally between seven and eight37) the leaching activity of these metals should be quite low. Methods Theoretically, a determination of the metals content of domestic wastewater should be possible based on a mass balance calculation. A mass balance is similar to an account- ing ledger in that all contributions are calculated individual- ly and totalled to produce the composite sum. The "sums" being sought in these mass balances are the concentrations of zinc, nickel, cadmium, and chromium in wastewater containing only human urine and feces. All other potential sources have been assumed to be negligible. A complete mass balance to determine these concentrations is summarized in Figure 1. 30 INTAKE FROM FOOD, WATER AIR, ABSORPTION THROUGH SKIN ‘ EXCRETED ‘ URINE FECES HAIR, FINGERNAILS, PERSPIRATION TOENAILS, ETC. r CONTRIBUTION TO WATER POLLUTION I ABSORBED I STORED IN BODY TISSUES FIGURE 1.--Metabolic Mineral Balance 31 This type of mass balance is not feasible since it would have to be carried out on each person utilizing the rest area toilet facilities. Instead, a literature review was conducted to Obtain representative concentration of each of the metals in urine and feces. The values obtained were discussed earlier in this paper. Next a compensation is made to account for the un- equal quantities of feces and urine in a unit volume of rest area wastewater. Finally, a dilution factor is used to account for the water entering the system, assumed to be metals-free except for the tap water background, which will dilute the urine and feces. The final equations will appear as follows: Eggggsgigil = [(Urine Conc Wt Factor);+(Feces Conc Wt Factor)] (1) Concentration [Dilution Factor] where: (Avg Excretion Volume)-F(Avg Dilution Volume) Dilution Factor = (Avg Excretion Volume) In addition, determination of the theoretical metals concen- tration was utilizing measured water consumption data instead of an average dilution factor. This analysis was performed on two representative sets of hourly data. The equation used to make the calculation was as follows: IQEIESIISII = [(Urine Conc Wt Fact)-+(Feces Conc)(Wt Fact)][No of Usersl Concentration (Volume of Water Used) (2) 32 The major weakness of this method is that each person counted as they entered the restroom is assumed to have uri- nated or defecated. Since such activities as combing hair or washing face do not involve addition of metals to the waste- water, a potential source of error can be created. In addi- tion, it is possible, and perhaps likely, that users might urinate without defecating but not vice versa thereby biasing the results. Experimental Methods Raw wastewater samples were obtained from the wet well at the Northbound rest area of Interstate 69 at Coldwater, Michigan. This rest area has been operated since 1969 as a combination information-welcome Station and modern restroom facility. On-site wells supply the water for the rest area, and wastewater treatment was provided by a two-cell faculta- tive lagoon system operated in parallel. A schematic plan for the water flow is provided in Figure 2. The sampling was done primarily from July 16-21, 1975. Samples were taken and immediately acidified with nitric acid. After collection, the samples were refrigerated until examina- tion. The 22 samples examined for metals content were selec- ted (see Appendix B) so as to minimize the bias of the time of day when they were taken. This was important due to the T HOT WATER HEATER I SINK FAUCETS 33 ’WELL I WATER METER I WATER STORAGE PRESSURE TANK f I COLD WATER I SINK FAUCETS, DRINKING FAUCETS TOILETS, URINALS I COLLECTOR SEWER I WET WELL I EJECTOR PUMP I ***SAMPLING POINT LAGOONS I COUNTY DRAIN Water Piping - Copper Wastewater Piping - Cast Iron Wet Well - Epoxy Resin and Coal Tar Coated Steel FIGURE 2.--Rest Area Water Flow Schematic 34 significant variation in rest area usage, and therefore, wastewater flow, between the daytime and early morning hours. Because of the dilute quantities of heavy metals in raw sewage, it was necessary to concentrate them to levels more easily measured. This concentration was accomplished by evaporation of 200 m1 of raw sewage to between 5-15 m1 on a steam table. The volume was then made up to 20 ml with distilled, de-ionized water. Following concentration, the samples were digested in a hot dilute hydrochloric-nitric acid solution (see 38 Following Appendix A for digestion-analysis procedure). vacuum filtration through a #42 Whatman filter, the samples were examined by atomic absorption spectroscopy on an Instrument Laboratories Model 251. Tap water and reagent blanks were run through the same procedure with the excep- tion that the reagent blanks were unfiltered. Results The theoretical calculations (see Appendix C) pro- duced the concentrations found in Table 6. These theoretical calculations are quite sensitive to changes in several assump- tions made, i.e., excretion volume and metals concentration, relative use weighting. Since significant variation in these parameters could occur between different individuals, the theoretical metals concentration could reasonably be expected to vary by a factor of ten. The calculated values shown in 35 TABLE 6.--Theoretical Metal Concentration in Rest Area Wastewater Metals Theoretical Concentration ngll) Avq. Flow Basis Instant HourLL=flgw Basis Cd 0.5 0.2 - 1.0 Cr 4.2 ' 1.8 - 8.9 Ni 4.0 1.7 - 8.3 Zn 190.4 84.1 - 400.6 36 Table 6 should be considered to be average concentrations only. The comparison of this theoretical range with the actual observed concentrations (see Appendix B) is made in Table 7. The measured values of water use per capita during the sampling period did not compare favorably with those pro- 4 This vided by the Michigan Department of State Highways. difference was probably due to the small number of random measurements on which this study's values are based. A more comprehensive study could easily match the Highway Department values. Discussion The theoretical calculations based on Equations 1 and 2 correspond to the actual observed concentrations for cadmium and nickel. The observed chromium concentration was slightly higher than expected, but this could have been the result of experimental error. One standard deviation of the wastewater chromium concentrations (see Appendix 8) extends into the theoretical range. The observed concentrations of zinc did not compare favorably to the theoretical calculations. There was almost certainly experimental error. The quantities of zinc in the blanks may have been the result of insufficient ion exchange in the distilled water apparatus. This contamina- tion should have pushed the zinc concentrations to much greater levels. Instead, no human excretory zinc contribution was 37 .m xwucmaa< cw cm>wm mew mpwo 3mm ..am» I 3mm u :o_u:nrspcou cowpumcpazm qumm mcomumcucmucoo cams mew mp o P\m: cowuaawgucoo ovummsoo 8;“ m m ep m— m_ mm —v _v p\m: _\m: ecmum: amp «cmpmzwummz 3am mmg< ammm gmpmzupou an :N van .mz .cu .uuuu.n m4mFucF «mev mEFF memo .ucou cN .ucou Fz .ucou cu .ucou cu opFamU\mm: mm: cmum: ngzo: mmg< ummm mewzuFou um mama um>gmmnori.Fm m4mFucF rammmv oEFF mama .ucou 2N .ucou Fz .ucou to .ucou vu mpFawuxmm: mm: Lopez ngso: Fu.p=ouv Fm mFaEF 51 TABLE 82.--Statistica1 Results (Mean :lSTD. Deviation) Tap Water Raw Wastewater Metal Concentrations (pg/t) Concentrations (pg/t) Cd <1 <1 Cr 20 i 3 35 _+_ 21 Ni 14 i 6 19 i 2 Zn 106 i 8 106 _+_ 40 Hourly Water Use = 195.2 : 157.5 gal 55 i 46 5.95 i 9.45 Individuals per Hour Water Use per Capita APPENDIX C APPENDIX C Calculation of Theoretical Metal Concentrations by Equation 1: (Angxcretion Volume)(Ayngilution Volume) (Avg Excretion Volume) Dilution Factor (Feces Conc Wt Factor)-I(Urine Conc Wt Factor) (Dilution Factor)(Avg Excretion Volume) Theor W.W. Conc = Assumptions: Average Water Use15 = 2.5 gallons/capita or 9.5 liters/capita Weighting Factors (for relative use)]5: 15% Defication 85% Urination Average Volume of Excretion16: Urine - 1400 mt/day Assume 300 melexcretion Based on 5 excretions/day Feces - Assume 300 mt/excretion Based on 1 excretion/day Dilutioanactor = (9°50+3g'312 = 32.7 a 33 Theor Cd Conc.: (31 pg/excr -O.l§)-+(O.3 nggxcr- 0.85) 33 (0.3 R/excr) = 0.5 uQ/B 52 53 Theor Cr Conc.: (270 ug/excr- O.15)(1.7 ug/excr- 0.85) 33 (0.3 t/excr) = 4.2 ug/t Theor Ni Conc.: (258 ug/excr- O.15)(O.5 pg/excr- 0.85) 33 (0.3 t/excr) = 4.0 pg/B Theor Zn Conc.: (12,000 ug/excr -0.l§)(100 ug/excr -O.85) 33 (0.3 t/excr) = 190.4 ug/t APPENDIX D APPENDIX 0 Calculation of Theoretical Wastewater Metal Concentrations by Equation 2: Theor W W Conc = [(Feces Conc -Wt Fac;)-I(Urine Conc-IWt Fact)][# Users] (Volume Water Used) Example 1: Upper Limit Hourly Water Use = 184 gallons = 696.4 liters Number of Users = 148 Theor Cd Conc.: [(31 pg/excr -O.15)-+(0.3 ug/excr- 0.85)][148] (696.42) = 1.0 ug/C Theor Cr Conc.: [(270 ug/excr- 0.15)+-(l.7pg/excr- 0.85)][1481 (696.42) = 8.9 ug/B Theor Ni Conc.: [(258 ug/excr- O.15L+-(0.5 ug/excr- 0.85)][1481 (696.4C) = 8.3 ug/R Theor Zn Conc.: [(12,000 ug/excr -O.15)-+(1OO ug/excr- 0.85)][1481 (696.41) ' = 400.6 ug/B 54 55 Example 2: Lower Limit Hourly Water Use = 178 gallons = 672.8 liters Number of Users = 30 Theor Cd Conc.: [(31 ugjexcr o0.15)-+(0.3_pg/excr -O.85)][30] (672.82) = 0.2 ug/B Theor Cr Conc.: [(270 pg/excr -0.15)-+(l.7 pg/excr- 0.85)][301 (672.82) = 1.8 ug/B Theor Ni Conc.: [(258_pg/excr -O.15)-+(0.5pg(excr- 0.85)][301 (672.82) = 1.7 ug/2 Theor Zn Conc.: [(12,000_pgjexcr -0.15)-+(1OO pg/excr- O.85)1[30] 672.82) = 84.1 ug/B APPENDIX E FeoFva oFoEexem use .estmsxus .erNFsmF FoFva seoqm use apnea F0~0Fv seFm use smsms Ammva .Fe um mcwmmu AFeva 0.6.00me 0:0 Lmumogcum mmusmsmwwm 0m m00.0 Fo.o 000.0 000.010F00.0 xFFz mmo.0 No.0 F00.0 eo.e EsoFe sees: Nm0.0 mFo.o mF0.o 0 oueEOF mmo.0 FF0.0 00.0 0m0.0 Foo.o ouepos Fmemse umgsFFosisosv seaeu eressom eer>oFmosum~0 asessmu ssmummz .<.m.0 Asussou .mmFsusuou mzoFse> sF Fpsmsz um: Easy uoou m>Fuumem sF Estue011.Fm 000