Disposal Of Municipal Sewage Sludge Research Articles

Simultaneous sorption of Cd, Cu, Ni, Zn, Pb, and Cr on soils treated with sewage sludge supernatant

Disposal of sewage sludge creates the potential for heavy metal accumulation in theenvironment. This study assessed nine soils currently used as Dedicated Land Disposal units(DLDs) for treatment and disposal of municipal sewage sludge in the vicinity of Sacramento,California. Adsorption characteristics of these soils for Cd, Cu, Ni, Zn, Pb, and Cr were studiedby simultaneously mixing these elements in the range of 0-50 µmol L-1 with sludgesupernatant and reacting with the soil using a soil:supernatant ratio of 1:30, pH = 4.5 or 6.5, andconstant ionic strength (0.01 M Na-acetate). The concentration of metals in the supernatant wasdetermined after a 24 hr equilibration period. Adsorption isotherms showed that metal sorptionwas linearly related to its concentration in the supernatant solution. The distribution coefficientKd (Kd = concentration on solid phase/concentration in solution phase) was computed as theslope of the sorption isotherm. The distribution coefficients were significantly correlated to soilorganic matter content for Ni, Cu, Cd, and Pb at pH 4.5 and for Ni, Cu, Zn, and Cd at pH 6.5.There was also a correlation between Kd and soil specific surface area but no relationship to othersoil properties such as CEC, clay content, and noncrystalline Fe and Al materials. Therefore, soilorganic carbon and surface area appear to be the most important soil properties influencing metaladsorption through formation of organo-metal complexes. The Kd values for all elements werehigher at pH 6.5 than at 4.5. Selectivity between metals resulted in the following metal affinitiesbased on their Kd values: Pb>Cu>Zn>Ni>Cd≈Cr at pH 4.5 andPb>Cu≈Zn>Cd>Ni>Cr at pH 6.5.

Metal Uptake by Agricultural Plant Species Grown in Sludge-Amended Soil Following Ecosystem Restoration Practices

The disposal of municipal sewage sludge is an important environmental problem presently facing society. Because sludge is rich in plant nutrients such as nitrogen and phosphorous, land application as a fertilizer has been proposed as a cost-effective means of disposal. This method of disposal, however, is frequently the subject of public health concern since municipal sludge may contain heavy metals that potentially could be introduced into the human food chain. This study examined metal concentrations in two agricultural species at a study site where ecosystem restoration practices (liming and tilling) had been conducted for 5 years following 11 years of sludge enrichment. 11 refs., 2 tabs.

Effects of land disposal of municipal sewage sludge on fate of nitrates in soil, streambed sediment, and water quality

This study was undertaken to determine the effects of sewage-sludge disposal at the Lowry sewage-sludge-disposal area, near Denver, Colorado, on ground- and surface-water quality, to determine the fate of nitrates from sludge leachate, and to determine the source areas of leachate and the potential for additional leaching from the disposal area. Sewage-sludge disposal began in 1969. Two methods were used to apply the sludge: burial and plowing. Also, the sludge was applied both in liquid and cake forms. Data in this report represent the chemical composition of soil and streambed sediment from seven soil- and four streambed-sampling sites in 1986, chemical and bacterial composition of ground water from 28 wells from 1981 to 1987, and surface-water runoff from seven water-sampling sites from 1984 to 1987. Ground water samples were obtained from alluvial and bedrock aquifers. Samples of soil, streambed sediment, ground water and surface water were obtained for onsite measurement and chemical analysis. Measurements included determination of nitrogen compounds and major cations and anions, fecal-coliform and -streptococcus bacteria, specific conductance, and pH. Thirteen wells in the alluvial aquifer in Region 3 of the study area contain water that was probably affected by sewage-sludge leachate. The plots of concentration of nitrate with time show seasonal trends and trends caused by precipitation. In addition to yearly fluctuation, there were noticeable increases in ground-water concentrations of nitrate that coincided with increased precipitation. After 3 years of annual ground-water-quality monitoring and 4 years of a quarterly sampling program, it has been determined that leachate from the sewage-sludge-disposal area caused increased nitrite plus nitrate (as nitrogen) concentration in the alluvial ground water at the site. Soil analyses from the disposal area indicate that organic nitrogen was the dominant form of nitrogen in the soil. As a result of investigations at the research site, it has been determined that a potentially large source of contamination exists in the soils of the study area owing to increased concentrations of nitrogen, sodium, calcium, magnesium, sulfate, bicarbonate, and chloride because of sewage disposal. Continued monitoring of surface and ground water for nitrogen and the other ions previously mentioned is required to assess long-term effects of municipal sludge disposal on water quality.

Benthic Distribution of Sewage Sludge Indicated by Clostridium perfringens at a Deep-Ocean Dump Site

Clostridium perfringens in sediment samples collected at the Deep Water Municipal Sewage Sludge Disposal Site (also called the 106-Mile Site), off the coast of New Jersey, was enumerated. The counts of C. perfringens found in sediment samples collected within and to the southwest of the 106-Mile Site were significantly elevated (P < 0.01) compared with counts of samples from reference stations of similar depth (2,400 to 2,700 m), topography, and distance from the continental shelf, indicating that the benthic environment was contaminated by sewage dumping at this site. Low counts of C. perfringens in sediment samples collected at stations between the base of the continental shelf and the 106-Mile Site indicated that coastal runoff was not a significant source of contamination. Elevated counts were observed for samples up to 92 km to the southwest, whereas low counts were obtained for samples from stations to the east of the 106-Mile Site. This distribution is consistent with previous model predictions of sludge deposition. In areas heavily impacted by sludge dumping, C. perfringens counts were generally highest in the top 1 cm of sediment and exceeded 9,000 CFU g (dry weight) of sediment. The patterns of C. perfringens dispersal observed in this study have proved useful for selection of heavily impacted areas and control stations for further ecological evaluation by a multidisciplinary research team.

Stable isotope evidence for entry of sewage-derived organic material into a deep-sea food web

CHRONIC pollution of the open ocean has occurred since 1986 through disposal of municipal sewage sludge at a deep-water (∼2,500 m) dumpsite off the coast of New Jersey. Dispersal and dilution of sewage particulates in surface waters were presumed to be sufficient to prevent or minimize accumulation of detectable amounts of sewage-derived material on the sea floor. Using stable isotope ratios of carbon, nitrogen and sulphur as tracers of sewage-derived organic material, we show here that this material reaches the sea floor and enters the benthic food web, specifically through surface-deposit feeding activities of the urchin, Echinus affinus and the sea cucumber, Benthodytes sanguinolenta.

Estimates of the seafloor area impacted by sewage sludge dumped at the 106-mile site in the mid-atlantic bight

Approximately 8 × 10 6 wet tons of sewage sludge is dumped annually at the 106-Mile Deep Water Municipal Sewage Sludge Disposal Site, 185 km off the New Jersey coast (Sano, 1989). A simple particle-tracking model is used to estimate the areas of sludge deposition using current meter observations made as part of the Mid-Atlantic Slope and Rise (MASAR) Study (Brown et al., 1987) and Lavelle et al.'s (1988) settling velocity distribution for sewage sludge. Model results indicate that sewage particles settle primarily to the southwest of the dump site due to the mean southwesterly flow throughout the water column. Only the coarser fraction (particles with settling velocities greater than 0·04 cm s −1), about 23% of the sludge discharged, is predicted to settle on the seafloor within 350 km of the site. The model predicts a maximum flux in the southwestern quarter of the site of 60 mg m −2 day −1 which decreases to about 25 and 1 mg m −2 day −1 at distances of approximately 50 and 350 km to the southwest, respectively. Little material is predicted to reach the shelf and the finer particles are assumed to be widely dispersed in the water column. These estimated fluxes compare with a natural particle flux of 100–150 mg m −2 day −1 as measured by sediment traps to the north of the 106-mile site (Biscaye et al., 1988). Field studies to assess the effects of sludge dumping on benthic organisms should initially focus on the region 0–50 km southwestward of the site.

Reproductive Success of Columbian Black-Tailed Deer in a Sewage-Fertilized Forest in Western Washington

Disposal of municipal sewage sludge is a problem of national importance (U.S. Environmental Protection Agency 1972, Cairns 1978, Stearns and Ross 1978). Commonly used disposal methods (incineration, wetland filling, freshwater dumping, and ocean dumping) have widely recognized negative environmental impacts. Because sludges contain high levels of nitrogen and plant macronutrients, it may be possible to defray disposal costs by fertilizing agricultural, range, and forest lands with sludge. In 1973 the College of Forest Resources, University of Washington, began a cooperative effort with metropolitan Seattle to examine the feasibility of fertilizing soils of the Tsuga heterophylla Zone of western Washington with sludge for silvicultural purposes. Because glacial soils of this region are typically nitrogen-poor, the growth rate of economically important conifers can be substantially increased by sludge amendment (Edmonds and Cole 1977). This increased wood yield may defray disposal costs (Taggart and Schroeder 1980). Incidental to the impact of sludge fertilization on wood yield is the potential for altering wildlife habitat through the fertilization of understory vegetation. The game animal of particular interest in western Washington is the Columbian black-tailed deer (Odocoileus hemionus columbianus). Because diet quality has frequently been associated with reproductive success in Odocoileus (Cheatum and Severinghaus 1950, Taber 1956, Forbes 963, Verme 1965, Murphy and Coates 1966, Dechert 1968), it was hypothesized that forest fertilization with sewage sludge would increase herd productivity. The objective of this paper is to document that sludge application increased the crude protein content of key deer forage items and that female deer exploiting sludge-amended areas recruited more fawns to the 6-month age-class than did controls.

Optimization of Subsurface Injection of Municipal Sewage Sludge

AbstractA dynamic programming model was used to determine the optimal yearly application rates for on‐land disposal of municipal sewage sludge. The model incorporated economic information and a soil nitrogen balance to find application rates which resulted in minimal cost while maintaining an acceptable level of environmental quality. Based on input conditions for Boulder, Colorado, the model suggests an average optimal annual application rate of 10.5 metric tons/ha at a net cost of $32.33/metric ton.A sensitivity analysis was performed in which certain input parameters, including nitrogen content of sludge, mineralization rates, allowable nitrate leaching losses, maximum addition of sludge organic nitrogen, land costs, and cash price of crops were identified as most significant.

Trace metal concentrations in two shellfish species of commercial importance.

The Public Health Service (Shellfish Sanitation Branch) continually collects and maintains data on metal levels in shellfish from approved shellfish areas. On the East Coast, three species are surveyed: the quahaug, Mercenaria mercenaria; the surf clam, Spisula solidisma; and the eastern oyster, Ostrea virginica. While a standard for cadmium in shellfish does not exist, the highest value for this metal in any of these shellfish from approved areas is 1.9 ppM (wet wt.) (PHS data, April 1976). In the present Public Health Program, neither the sea scallop Placopecten magellanicus nor ocean quahaug Arctica islandica are regularly surveyed (LAMB, 1976). Both species are found in deeper continental shelf areas and hence presumably farther removed from coastal sources of contamination. In recent years in the mid-Atlantic, the marketing of the sea scallop has become increasingly inportant with landings between 1974 and 1975 increasing by 81 percent (PILEGGI and THOMPSON, 1976). Furthermore, more than 80 percent of these commercial landings were caught between 12 and 200 miles offshore (a total of 3557 kg, wet weight with shell). There is at present much more limited fishing for the ocean quahaug; however, the potential for commercial exploitation is great (SAILA and PRATT, 1973). In viewmore » of the present importance of the sea scallop and the potential of the quahaug in the shellfish industry, in addition to the lack of published information on cadmium levels in these species, we present here some data on cadmium (and other trace metals) in these organisms. Samples are from a region of the continental shelf (Figure 1) which at present is reportedly fished for scallops (SAILA and PRATT, 1973). This area is removed from any large-scale inputs of trace metals from human activity (e.g., dredge spoils, industrial or municipal sewage sludge disposal).« less