Heavy metal and volatile organic chemical removal and treatment in on-site wastewater systems

In Wisconsin, motor vehicle waste fluids (MVWF) enter catch basins along with rinse waters and are discharged to drainfields (soil absorption systems) after mixing with domestic wastewater in a septic tank (systems installed prior to 1992). The purpose of this study was to determine if removal/treatment of heavy metals and volatile organic chemicals (VOCs) found in spent oils, greases, and solvents occurs in drainfields that receive MVWFs. Soil samples were collected beneath and soil gas samples were collected above three gravel beds in drainfields installed in loamy sand or silt loam soils. Cadmium, chromium, and lead concentrations in soil 15 cm and greater beneath beds in loamy sand and silt loam soils were similar to background concentrations. Heavy metals in drainfields would most likely be found in the clogging layer at the infiltrative surface of gravel and soil. The VOCs 1,3,5-trimethylbenzene and m- and p-xylenes were found beneath beds in loamy sand soils; concentrations of detected VOCs ranged from 20–270 mg kg^?1. Volatile organic chemicals were not detected beneath the bed in silt loam soils. Drainfields in loamy sand soil appear to provide less treatment of VOCs compared to drainfields in silt loam soils. Volatile organic chemicals were found in soil gas above drainfields in both soil types. Thus, some VOCs diffuse from the drainfield to the soil surface.     

Trace organics in septic tank effluent

This paper reviews the available information and presents the results of a study undertaken to estimate the presence and level of certain trace organics in wastewater samples collected from a septic tank in an individual household, from a lift station, and from a waste treatment lagoon near Regina, Canada. Out of 11 priority pollutants analyzed, 6 priority pollutants — chloroform, bromodichloromethane, toluene, benzene, methylene chloride and tetrachloroethylene — were detected in the samples. Benzene and bromodichloromethane were dominant. Methylene chloride and tetrachloroethylene could not be quantified at the low concentrations present. Chloroform was present in the lagoon effluent sample once at a concentration of 0.03 μg L^?1. Toluene was not present either in the septic tank effluent or in the lagoon effluent. Benzene was present in the septic tank effluent (max. value 450 μg L^?1) and in the lagoon effluent (max. value 120 μg L^?1). Bromodichloromethane was present in the septic tank effluent and lagoon effluent at concentrations lower than 1.10 μg L^?1. The trace organics in the septic tank effluent and lagoon effluent at these comparatively low concentrations may not pose any significant risk either to aquatic life or to public health, taking into account the attentuation capacity of the soil and the dilution usually available.     

Treatment of Septic Effluent for Fecal Coliform and Nitrogen in Coarse-textured Soils: Use of Soil-only and Sand Filter Systems

Groundwater effluent sample collectors(zero-tension lysimeters) were installed directlybelow the drainfields of three residential onsitetreatment systems in the Clover/Chambers Creek aquiferregion of Pierce County near Tacoma, WA. The use of asplit effluent delivery system from the septic tank,where half the effluent was delivered under pressureto a normal native soil-only filter system and halfwas delivered to a sand filter system, allowed thedirect comparison of the two commonly-utilized septicsystems for treatment levels. Septic tank effluent(from the septic tank) and percolating water (between0.3 and 0.9 m beneath the effluent distributionlines) was collected between May 1991 and April 1994on 30 occasions. Samples were analyzed for fecalcoliform bacteria, nitrate, nitrite, ammonium andtotal reduced (Kjeldahl) nitrogen. Results of thisstudy indicate that the use of sand filters greatlyincreased removal of fecal coliform bacteria and totalnitrogen. Soil-only filter systems had an average of91% removal of fecal coliforms and 47%of total N; whereas sand filter systems had an averageof 99.8% removal of fecal coliforms and 80% of total N.     

The amount of heavy metals derived from domestic sources in Japan

The amount of heavy metals discharged from daily life was estimated in order to know the origin of the metals contained in the sewage sludge which is produced in the wastewater treatment plant treating only domestic wastewater. The amounts of the metals discharged from our daily life were estimated to be in the range of 0.2 to 0.3 for Cd, 1.6 to 1.9 for Ni, 3.5 to 6.8 for Pb, 0.8 to 1.4 for Cr, 8.2 to 19.3 for Mn 9.4 to 55.8 for Cu, 44.3 to 62.7 for Zn and 111 to 293 for Fe in mg.d^–1 per person, Using these data, the cycle of the metals in our daily life was discussed in relation to land application of sewage sludge.     

Pollution of ground water by nutrients and fecal coliforms from lakeshore septic tank systems

The fate of wastewater effluents discharged from 17 septic tank disposal systems located near the shores of eight lakes in northeastern and eastern New York State was investigated. Fecal coliforms chloride, conductivity, dissolved 0₂, phosphate and various forms of N in ground water samples were analyzed. Of 46 ground water samples, 23 were found to be highly contaminated and 16 slightly contaminated. Only 7 were not contaminated by the wastewater effluent. Seventeen of the 23 highly contaminated samples were collected within 30.5 m of the discharge point of the septic systems. Eleven of these were collected from ground water less than 122 cm below ground level. Eight of the 16 slightly contaminated samples and 3 of the 7 noncontaminated samples were collected at a distance greater than 30.5 m. The depth to the ground water from ground surface and the distance of the ground water from the discharge point of the sewage system are main factors influencing pattern and severity of ground water contamination. This survey indicated that significant nutrient and fecal coliform contamination of lakeshore ground waters was occurring.

     

Nitrilotriacetic acid removal in septic tanks: A field study

The removal of nitrilotriacetic acid (NTA) dosed to two full-scale septic tanks each connected to a single dwelling was monitored weekly over a period of 75 weeks. Nitrilotriacetic acid in the septic tank effluent was detected in samples diluted at least 25 times by a differential pulse polarographic technique. After an initial period of stabilization, concentrations of NTA in the effluent at both sites were always > 10 mg L^?1. Mean five-weekly estimated removals of NTA during the last 50 weeks of the study ranged from 33 to 52%. Removal of NTA was probably by solids adsorption only as no acclimatization period or overall increase in removal during the investigation was apparent.     

Deposit of zinc and manganese in an aqueous environment mediated by microbial mats

Microbial mats have been developed to sequester heavy metals from contaminated water. Mixed populations of photosynthetic and heterotrophic bacteria, dominated by Scillatoria spp., were developed for metal tolerance and integrated into a durable, self-sustaining community of microbes stimulated by and attached to ensiled grass. The mat was immobilized on glass wool and layered in flow-through baffled tanks. After allowing 8 weeks for the maturation of the mat, mixed solutions of Zn and Mn (15–16 mg L^?1) were passed through a three-tank experimental series. Effluent from each tank was first sampled and then applied to the next tank. This procedure was repeated in triplicate and with six applications of new metal solution per three-tank series. By the third tank, the target metal concentration <1 mg L^?1 was always achieved. Mean percentages of the initial influent concentration removed by tanks 1, 2 and 3, respectively, were 72, 93 and 98 for Zn and 78, 97 and 99 for Mn. Mean metal concentrations in the effluents (average of 6 applications) were, for tank 1: Zn (mg L^?1) 5.0, Mn (mg L^?1) 4.2; for tank 2: Zn 1.6, Mn 0.75; for tank 3: Zn 0.53, Mn 0.19. Mean effluent concentrations from each of the three sequential treatments (average of 6 applications per tank) were for Zn (mg L^?1) 5.0, 1.6 and 0.53; for Mn (mg L^?1) were 4.2, 0.75 and 0.19. Thus target concentrations were reached in experimental tank 2 for Mn and tank 3 for Zn. Metal removal in the control tank series, containing glass wool only, was 37% for Zn and 5% for Mn (average of 6 applications). Oxygen and redox potential analyses of the mat/glass wool matrix revealed a heterogenous structure of anoxic and oxic zones. Zeta potential analysis of the mat samples identified a mat surface charge ranging from ?12.3 to ?69.2 mV. Various metal removal mechanisms possibly involved with metal sequestering include surface binding to the mat or to mat exudates trapped within the glass wool, precipitation of the metals with anions present in the oxic/anoxic zones, mat mediation of the water conditions in favor of metal-oxide precipitation and active transport of the metals into the cell.     

The influence of process parameters on the removal of heavy metals in activated sludge

The behavior of six heavy metals in an activated sludge pilot plant under conditions of normal and elevated influent metal concentrations has been studied. Percentage heavy metal removals at sludge ages of 4, 9, and 12 d were more consistent when metals were added to the system, possibly as a result of lesser variations in heavy metal speciation in the settled sewage, and the greatest degree of accumulation of heavy metals by the biomass occurred at the 12 d sludge age. When shock loads of heavy metals were introduced into the system, their concentrations in the effluent did not immediately rise in proportion; however, heavy metal removal efficiencies were similar under steady state conditions of normal and elevated influent metal concentrations. Cadmium, Cu, and Ni were largely soluble in the effluent samples, but Cr, Pb, and Zn were predominantly insoluble, indicating that particulate forms of these metals may escape removal in secondary sedimentation. The high degree of Ni solubility in the settled sewage and final effluent reflected its consistently poor removal in the process. The two most soluble metals, Cu and Ni, appeared to be associated to a large degree with high molecular weight substances in the settled sewage and final effluent, possibly influencing their availability for uptake by the biomass.     

Application of Adsorption and Ultrafiltration Processes for the Pre-treatment of Several Industrial Wastewater Streams

In this work ultrafiltration (UF) was coupled with suitable minerals and dried activated sludge for the pre-treatment of several industrial wastewater streams. The aim was to decrease heavy metal concentrations to low levels so that wastewater can be safely discharged into municipal sewers or biological wastewater treatment can take place without biomass inhibition problems. Industrial wastewater originating from metal plating, chemical and textile industries was employed. The experiments were conducted in a reactor where the UF membrane module was immersed. UF reduced the amount of heavy metals, but the performance was variable with removal efficiencies ranging from 20 to 99.7?%, depending on the metal type and on the wastewater initial characteristics. The prevailing wastewater characteristics were the pH, the presence of certain anions, the suspended solids concentration and the presence of competing cations. The addition of activated sludge and/or minerals could further increase heavy metal removal through the process of sorption. UF assisted by minerals could achieve variable colour and COD removal ranging from 22 to 94?% and 58 to > 99.9?% respectively. Minerals resulted in membrane fouling mitigation, while sludge adversely impacted on fouling.     

Influence of sewage sludge and heavy metals on nematodes in an arable soil

Summary The abundance of nematodes was investigated in agricultural plots treated in three different ways, the first with no treatment, the second with 300 m³ ha^-1 a^-1 raw sewage sludge and the third with 300 m³ ha^-1 a^-1 sewage sludge with the addition of heavy metals. The nematodes were determined down to the genus and were assigned to five feeding groups. Total nematode numbers were highest in the site treated with sewage sludge and heavy metals. The smallest total numbers were found in the control site. The plant-feeding nematode genera showed different patterns of abundance depending on the sludge treatment and heavy metal content. For the mycophagic and bacteriophagic nematodes, numbers increased with the amount of sludge, especially in the sites with a higher heavy metal content. The family Rhabditidae was the most numerous group in the sludge plus heavy metals treatment. In contrast to these findings, the omnivorous nematodes were very rare in the sludgetreated plots and were completely absent in plots treated with sludge plus heavy metals, whereas predatory nematodes were numerous only after the application of sludge alone.     

再生水短期灌溉对土壤-作物中重金属分布影响的试验研究

再生水是农业灌溉的重要水资源。该文在田间小区开展了为期4年的再生水灌溉试验，研究了重金属在土壤-作物系统中的转化与分布规律。结果表明：短期内重金属在土壤中的累积不明显，且土壤和作物籽粒中的重金属含量都远低于国家标准规定的允许值，再生水短期灌溉对土壤环境和作物均不会造成污染影响；同时，不同再生水灌溉水量条件下，土壤中重金属含量无显著差异，再生水灌溉带入土壤中的重金属量小于作物收获所带走的重金属量，带出量和带入量对土壤中重金属平衡的影响较小。     

DISTRIBUTION AND SEQUENTIAL EXTRACTION OF SOME HEAVY METALS FROM SOILS IRRIGATED WITH WASTEWATER FROM MEXICO CITY

A sequential extraction procedure was used to fractionate Cu, Cd, Pb and Zn in 4 soil profiles into the designated forms of water soluble + exchangeable, organically bound, carbonate and Mn oxides bound. Soil profiles were obtained from the Rural Development District 063, State of Hidalgo, which have been irrigated with wastewater coming out of the basin of Mexico. The total heavy metal contents range as follows: Cu, 8.9 to 86.5 mg kg^-1 Cd, 0.86 to 5.07 mg kg^-1 Pb, 18.1 to 131.7 mg kg^-1 and Zn, 101 to 235.5 mg kg^-1. The highest concentrations of total heavy metals were found in the surface layers at all soil profiles. Sequential chemical fractionation indicated that the four metals were predominantly associated with the organic fraction at most soil samples. The contents in all fractions of the four metals showed a decrease with depth which has been explained by the variations in the organic matter and CaCO₃ contents in the different layers of soils. These soil properties were also the most important variables in the biological availability of the metals in these soils.     

Daily chemical variability of domestic septic tank effluent

Effluent from the septic tanks of five households was sampled daily for 15 days. Temperature, redox potential, conductivity and biochemical oxygen demand (BOD₅) were measured and samples were analyzed for N, P, Ca, Mg, Na, K, Zu, Zn, Cd, Cr, Pb, Mg, and linear alkylate sulphonate (LAS). Samples from the five households differed in the values obtained but the differences were small. Little daily variation occurred in the effluent from any one household. The effluent was in a reduced and anaerobic condition with almost all the N and P occurring in the inorganic form in solution. The effluent concentration N was about 100 mg l^?1 and P concentration about 15 mg l^?1. The mean annual N and P loading in the effluent over the five households was 3.8 kg N/head yr and 0.6 kg P/head · yr. Copper and Zn were the only trace metals of any significance and their concentrations were less than in tap water. The chemical composition of the effluent was very similar to that found in New Zealand, Canada, and U.S.A.     

Recycling of water for irrigation: Persistence of enteroviruses in sewage effluent and natural waters receiving the effluent

A virological analyses of a sewage treatment plant which provided chlorinated, activated sludge treated sewage effluent to irrigate a complete two-year crop of sugarcane was made. The raw, the activated sludge treated and the chlorinated sewage effluent, as well as streams and a harbor receiving sewage effluents were concentrated by either the polymer two-phase, PE-60, Al(OH)₃, protamine sulfate, or cellulose membrane method and assayed for human enteric viruses. Viruses were recovered from 100% (11/11) of the raw sewages tested at concentrations ranging from 27 to 19 000 PFU l^?1 while 76% (13/17) of the activated sludge treated effluent was positive at concentrations ranging from 7 to 5222 PFU l^?1. After chlorination, 58% (31/53) of the samples was positive for virus at concentrations ranging from 2 to 750 PFU l^?1. Human enteroviruses were also isolated from shallow flowing streams at distances up to 3 mi (5 km) from the closest known sewage effluent discharge point and from a harbor approximately 0.5 mi (0.8 km) from the point of sewage discharge entering the harbor. The viruses most often isolated were echovirus 7, coxsackievirus B-4, B-5 and poliovirus 1, 2, and 3. These results indicate that although activated sludge treatment plus chlorination remove approximately 90% of the virus from the raw sewage, the final treated sewage effluent, which is normally discharged into a stream and in this experimental study to irrigate sugarcane, still contains a significant concentration of infectious viruses. Furthermore, the recovery of enteroviruses from waterways at points distant from the sewage treatment plants indicates that sewage-borne viruses persist in natural water environment. The significance of enteric viruses in waters accessible to the public and used for irrigation purposes remains to be determined.     

Relationships of Heavy Metals in Natural Lake Waters with Physico-chemical Characteristics of Waters and Different Chemical Fractions of Metals in Sediments

The relationships between heavy metal concentrations and physico-chemical properties of natural lake waters and also with chemical fractions of these metals in lake sediments were investigated in seven natural lakes of Kumaun region of Uttarakhand Province of India during 2003–2004 and 2004–2005. The concentrations of Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb in waters of different lakes ranged from 0.29–2.39, 10.3–38.3, 431–1407, 1.0–6.6, 5.3–12.1, 12.6–166.3, 0.7–2.7 and 3.9–27.1 μg l^?1 and in sediments 14.3–21.5, 90.1–197.5, 5,265–6,428, 17.7–45.9, 13.4–32.0, 40.0–149.2, 11.1–14.6 and 88.9–167.4 μg g^?1, respectively. The concentrations of all metals except Fe in waters were found well below the notified toxic limits. The concentrations of Cr, Mn, Ni, Cu, Zn, Cd and Pb were positively correlated with pH, electrical conductivity, biological oxygen demand, chemical oxygen demand and alkalinity of waters, but negatively correlated with dissolved oxygen. The concentrations of Cr, Ni, Zn, Cd and Pb in waters were positively correlated with water soluble + exchangeable fraction of these metals in lake sediments. The concentrations of Zn, Cd and Pb in waters were positively correlated with carbonate bound fraction of these metals in lake sediments. Except for Ni, Zn and Cd, the concentrations of rest of the heavy metals in waters were positively correlated with organically bound fraction of these metals in lake sediments. The concentrations of Cr, Mn, Ni, Cu and Zn in waters were positively correlated with reducible fraction of these metals in lake sediments. Except for Cd, the concentrations of rest of the metals in waters were positively correlated with residual fraction and total content of these heavy metals in lake sediments.     

Microbiological and chemical changes in two arable soils after long-term sludge amendments

 Sludge amendments increase the input of carbon and nutrients to the soil. However, the soil concentrations of heavy metals and xenobiotica can also increase due to sludge amendments, with possible effects on soil microorganisms and soil fertility. Therefore, we studied the effects on soil microorganisms and soil chemistry in two arable soils after 12 and 16 years of sewage sludge amendment (0, 1 and 3 dry matter ha^–1 year^–1). The sludge amendments were combined with nitrogen addition at three rates according to crop requirements, and all combinations were replicated 4 times, giving a total number of 36 parcels at each experimental site in a non-randomised block design. Univariate data evaluation as well as principal component analysis and discriminant function analysis (DFA) were used to identify differences between treatments in microbial and chemical parameters. The DFA showed that acid and alkaline phosphatase, potential ammonium oxidation and total nitrogen were the most important parameters to discriminate between a priori defined groups of sludge treatments. Among the heavy metals, copper showed the highest increase in soil concentration with sludge amendments, but this increase was still not high enough to have a significant influence on the measured parameters. None of the xenobiotica investigated was found in high soil concentrations. In conclusion, the present study showed that the sewage sludge affected several of the biological and chemical parameters investigated. However, no severe negative effects on soil microorganisms were detected at these moderate levels of sludge amendment. Received: 3 December 1998     

Geochemical Mobility and Bioavailability of Heavy Metals in a Lake Affected by Acid Mine Drainage: Lake Hope, Vinton County, Ohio

Sandy Run (Vinton County, southeastern Ohio, USA) is a stream receiving acid mine drainage (AMD) from an abandoned coal mine complex. This stream has been dammed to form Lake Hope. The heavy metal composition of waters (benthic and pore), sediments, and macroinvertebrates in the lake reservoir sediments were analyzed. Lake waters contained Mn as the heavy metal present in higher concentrations followed by Fe, Al, and Zn. Depletion of Fe and Al occurred from precipitation of less soluble Fe and Al oxides and hydroxides along Sandy Run before entering the lake, producing a high Mn water input into the reservoir. Concentrations of heavy metals in the sediments increased toward the dam area. Sequential extraction of metals in the sediments showed that the highest fractions of metals corresponded to the detrital fraction or eroded material from the watershed and metals associated with iron and manganese hydroxides. Heavy metals in the organic sediment fraction were low. Heavy metals from the AMD source, as well as sediments rich in heavy metals eroded from the watershed, were transported to the downstream dam area and stored at the bottom, producing the observed chemistry. Heavy metals in benthic waters also were sourced from the diffusion of ions from sediments and lake waters as variation in pH and redox conditions determined the flux at the sediment–water interface. Metal concentrations were measured within two deposit feeders, oligochaetes and chironomids, and compared to trends in physical metal concentration across the lake. For the four heavy metals with higher concentration in both benthic animals, the concentrations followed the trend: Fe?>?Al?>?Mn?>?Zn, which were similar to the bioavailable metals in the sediments rather than the pore or the benthic water where Mn was the most abundant heavy metal. Ingestion of sediment, not exposure to pore or benthic waters, appeared to be the main transfer mechanism for metals into the biota. Trends and patterns in animal metal concentrations across the lake were probably a complex process controlled by metabolic needs and metallic regulation and tolerance. Even when Mn was the highest concentration heavy metal in the pore waters, it was the lowest to bioconcentrate in the organisms. In comparison, Cd, the lowest concentration metal in the sediments, presented one of the highest bioaccumulation factors.     

Use of Power Plant Ash to Remove and Solidify Heavy Metals from a Metal-finishing Wastewater

This laboratory-scale study investigated initially the potential of heavy metal removal from a metal-finishing wastewater using fly and bottom ash from a power plant as coagulants. It was found that the maximum heavy metal content in the ash–sludge mix was obtained at a fly ash-to-bottom ash ratio of 1.5:1 and a stirring time of 3 h, which resulted in heavy metal removal (i.e., Cr, Ni, Cu, Zn, Cd, and Pb) in excess of 99%, with effluent concentrations below the corresponding regulatory standards of Thailand. Furthermore, the feasibility of using fly ash as an admixture to stabilize and solidify the ash–sludge mix generated previously was explored. Results indicated that the stabilization/solidification process can achieve a high level of heavy metal removal efficiency from the ash–sludge mix. The optimum ratio regarding chromium leaching was found to be 1:0.75:0.75 (cement:fly ash:ash–sludge). In addition, the compressive strength and the chromium leaching concentration of the solidified sludge were within acceptable levels for secure landfill disposal and/or use as a construction material.     

Accumulation of Heavy Metals in Wheat (Triticum aestivum L.) Seedlings Grown in Soils Amended with Electroplating Industrial Sludge

A glasshouse study was undertaken to evaluate the effect of lime-treated (0, 0.5, and 1%) industrial sludge amendments (10 and 20%) on wheat (Triticum aestivum L.) seedling growth and heavy metal accumulation in soils as well as in wheat seedlings. Industrial sludge–amended soil samples were filled in earthen pots (2 kg pot^?1) one week before planting and 7-day-old seedlings were transplanted in pots (3/pot) and were kept in a glasshouse. Diethylenetriamine pentaacetic acid (DTPA)-extractable metals and metals in seedlings increase with increasing doses of industrial sludge. Biomass and growth have been found to increase with increasing rates of sludge. It also enhanced heavy metal concentrations in wheat seedlings and followed the trend zinc (Zn) > lead (Pb) > copper (Cu) > cadmium (Cd). Lime enhanced the biomass and reduced the heavy metal concentrations in wheat seedlings. Although 20% treatments in both soils showed a significant enhancement in shoot length, metals like Pb reached beyond permissible limits.     

Groundwater pollution from a septic tile field

The characteristics of the groundwater below an existing septic tile field were studied during the summer of 1973. The concentrations for chemical constituents were found to be much lower in the groundwater compared to the septic tank effluent; however, these were quite high compared to background levels for the groundwater in the area, indicating the pattern of pollution that is taking place.