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PubMed2005

Cumulative and residual effects of repeated sewage sludge applications: forage productivity and soil quality implications in South Florida, USA.

BACKGROUND, AIM AND SCOPE: The cow-calf (Bos taurus) industry in subtropical United States and other parts of the world depends almost totally on grazed pastures. Establishment of complete, uniform stand of bahiagrass (BG) in a short time period is important economically. Failure to obtain a good BG stand early means increased encroachment of weeds and the loss of not only the initial investment costs, but production and its cash value. Forage production often requires significant inputs of lime, N fertilizer, and less frequently of P and K fertilizers. Domestic sewage sludge or biosolids, composted urban plant debris, waste lime, phosphogypsum, and dredged materials are examples of materials that can be used for fertilizing and liming pastures. Perennial grass can be a good choice for repeated applications of sewage sludge. Although sewage sludge supply some essential plant nutrients and provide soil property-enhancing organic matter, land-application programs still generate some concerns because of possible health and environmental risks involved. The objectives of this study were to evaluate the cumulative and residual effects of repeated applications of sewage sludge on (i) bahiagrass (BG, Paspalum notaturn Flügge) production over years with (1997-2000) and without (2001-2002) sewage sludge applications during a 5-yr period, and (ii) on nutrients status of soil that received annual application of sewage sludge from 1997 to 2000 compared with test values of soils in 2002 (with no sewage sludge application) in South Florida. METHODS: The field experiment was conducted at the University of Florida Agricultural Research and Education Center, Ona, FL (27 degrees 26'N, 82 degrees 55'W) on a Pomona fine sandy soil. With the exception of the control, BG plots received annual sewage sludge and chemical fertilizers applications to supply 90 or 180 kg total N ha(-1) yr(-1) from 1997 to 2000. Land application of sewage sludge and fertilizer ceased in 2001 season. In early April 1998, 1999, and 2000, plots were mowed to 5-cm stubble and treated with the respective N source amendments. The experimental design was three randomized complete blocks with nine N-source treatments: ammonium nitrate (AMN), slurry biosolids of pH 7 (SBS7), slurry biosolids of pH 11 (SBS11), lime-stabilized cake biosolids (CBS), each applied to supply 90 or 180 kg N ha(-1), and a nonfertilized control (Control). Application rates of sewage sludge were calculated based on the concentration of total solids in materials as determined by the American Public Health Association SM 2540G method and N in solids. The actual amount of sewage sludge applications was based on the amount required to supply 90 and 180 kg N ha(-1). Sewage sludge materials were weighed in buckets and uniformly applied to respective BG plots. Soil samples were collected in June 1997, June 1999, and in June 2002 from 27 treatment plots. In 1997 and 1999, soil samples were collected using a steel bucket type auger from the 0- to 20-, 20- to 40-, 40- to 60-, and 60- to 100-cm soil depths. Forage was harvested on 139, 203, 257, and 307 day of year (DOY) in 1998; 125, 202, 257, and 286 DOY in 1999; 179, 209, 270, and 301 DOY in 2000; and on 156 and 230 DOY in 2002 (no sewage sludge applications) to determine the residual effect of applied sewage sludge following repeated application. Forage yield and soils data were analyzed using analysis of variance (PROC ANOVA) procedures with year and treatment as the main plot and sub-plot, respectively. As a result of significant year effects on forage yield, data were reanalyzed annually (i.e., 1998, 1999, 2000, and 2002). RESULTS AND DISCUSSION: All sewage sludges used in this study were of class B in terms of USEPA's pathogens and pollutant concentration limit. Pathogen and chemical composition of the class B sewage sludge that were used in the study were all in compliance with the USEPA guidelines. The liquid sludge (SBS11) had the lowest fecal coliform counts (0.2 x 10(6) CFU kg(-1)) while the cake sewage sludge (CBS) had the greatest coliform counts of 178 x 10(6) CFU kg(-1). The fecal coliform counts for SBS7 was about 33 x 10(6) CFU kg(-1). Average soil test values in June 2002 exhibited: i) decrease in TIN (NO3-N + NH4-N), TP, K, Ca, Mg, Mn, and Fe; and ii) slight increase in Zn and Cu when compared with the June 1997 soil test results. The overall decrease in soil test values in 2002 might be associated with nutrient cycling and plant consumption. Although the average BG forage yield in 2002 (2.3 +/- 0.7 Mg ha(-1)) was slightly lower than in 2000 (3.5 +/- 1.2 Mg ha(-1)), yield differences in 2002 between the control (1.2 +/- 0.2 Mg ha(-1)) and treated plots (2.3 +/- 0.5 Mg ha(-1) to 3.3 +/- 0.6 Mg ha(-1)) were indicative of a positive residual effect of applied sewage sludge. This study has shown that excessive build up of plant nutrients may not occur in beef cattle pastures that repeatedly received sewage sludge while favoring long-term increased forage yield of BG. All sources of N (sewage sludge and AMN) gave better forage production than the unfertilized control during years with sewage sludge application (1997-2000) and also during years with no sewage sludge application (2001-2002). The favorable residual effects of applied sewage sludge in 2002 may have had received additional boost from the amount of rainfall in the area. CONCLUSIONS: Repeated applications of sewage sludge indicate no harmful effects on soil quality and forage quality. Our results support our hypothesis that repeated land application of sewage sludge to supply 90 and 180 kg N ha(-1) would not increase soil sorption for nutrients and trace metals. Results have indicated that the concentrations of soil TIN and TP declined by almost 50% in plots with different nitrogen sources from June 1997 to June 2002 suggesting that enrichment of nitrogen and phosphorus is insignificant. The concentrations of soil nitrogen and phosphorus in 2002 following repeated application of sewage sludge were far below the contamination risk in the environment. The residual effect of these sewage sludge over the long term can be especially significant in many areas of Florida where only 50% of the 1 million ha of BG pastures are given inorganic nitrogen yearly. RECOMMENDATION AND OUTLOOK: Successive land application of sewage sludge for at least three years followed by no sewage sludge application for at least two years may well be a good practice economically because it will boost and/or maintain sustainable forage productivity and at the same time minimize probable accumulation of nutrients, especially trace metals. Consecutive applications of sewage sludge may result in build up of some trace metals in some other states with initial high metallic content, but in this study, no detrimental effects on soil chemical properties were detected. The possibilities for economically sound application strategies are encouraging, but more and additional research is required to find optimal timing and rates that minimizes negative impacts on soil quality in particular or the environment in general. For proper utilization of sewage sludge, knowledge of the sewage sludges' composition, the crop receiving it, are absolutely crucial, so that satisfactory types and rates are applied in an environmentally safe manner. There is still much to be learned from this study and this investigation needs to continue to determine whether the agricultural and ecological objectives are satisfied over the longer term.

Animals↗
PubMed2003

Feeding of benthic foraminifera on diatoms and sewage-derived organic matter: an experimental application of lipid biomarker techniques.

Foraminiferal ecology at sewage outfalls has been investigated in numerous field studies over the last 30 years. Foraminifera have been frequently used as biomonitors of sewage pollution since they are both abundant and ubiquitous. Sewage outfalls have been demonstrated to have both positive and negative effects on adjacent foraminiferal populations, but it has never been shown conclusively why sewage affects foraminifera in these ways. Such information on the impact mechanisms of sewage pollution is essential if foraminifera are to be used as sewage pollution biomonitors, and also to understand the ecology of these important protists. One possible cause of a positive effect is the direct consumption of sewage-derived particulate organic matter (POM) by the foraminifera themselves. However this hypothesis has never been tested experimentally. Here, lipid (fatty acid and sterol) biomarker techniques were applied to study the ingestion of two potential food items by the foraminiferan Haynesina germanica in the laboratory. An experiment was conducted to confirm that the laboratory conditions were conducive to the survival and feeding of the foraminifera. In this experiment, foraminifera were provided with the pennate diatom Phaeodactylum tricornutum, which was considered to be a suitable food source. After 2 weeks, a four-fold increase in the levels of the diatom fatty acid biomarker, 20:5(n-3), in the foraminifera suggested that they had fed actively on the diatoms and survived under the experimental conditions. These experimental conditions were used in the main experiment, where foraminifera were fed the POM from sewage. Lipid biomarker analysis indicated that H. germanica did not consume secondary treated sewage-derived POM. Neither fatty acid profiles in the sewage nor coprostanol, the diagnostic human faecal sterol, were detected in foraminifera after exposure to the potential sewage food source. However, foraminifera may have consumed bacteria associated with the sewage in the experiment. The findings are discussed in terms of current EU legislation on sewage treatment that has affected the composition of sewage discharges, and therefore possibly reduced the nutritive value of sewage to the marine benthos.

Animals↗
PubMed2006

Persistence of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge-amended soil.

The application of sewage sludge as a fertilizer is a common method used to improve soil properties. However, sewage sludge may contain various organic pollutants including polycyclic aromatic hydrocarbons. In the present study, the persistence of PAHs in soils fertilized with different sewage sludge doses was compared in relation to the sewage sludge dose applied (30, 75, 150, 300 and 600 Mgha(-1)) and the content of the polycyclic aromatic hydrocarbons in them. The experiment was carried out in two blocks of experimental plots divided according to the type of plants grown: field plants and perennial-willow. Sewage sludge addition to soils resulted in an increase in the content of polycyclic aromatic hydrocarbons in these soils. This increase was proportional to the quantity of sewage sludge applied. The results obtained showed that during a 42/54-month period, more than half of the individual PAHs introduced into the soil with sewage sludge were degraded. The scope of dissipation depended on the sewage sludge dose and the use to which the area was put. In the experiment with the willow only in the case of the highest sludge dose was a decrease in the PAH content above 50% noted; whereas in the case of the experiment with the field plants, it was higher by 50% for all sewage sludge doses. In experiment with field plants the highest scope of individual PAH disappearance was observed in the soil with the sewage sludge dose amounting to 300 Mgha(-1). In experiment with willow a relatively high dissipation of individual PAHs (>50%) was found in the treatment with the highest sludge dose (600 Mgha(-1)). A wider PAH dissipation range in the experiment with field plants was conditioned by the more favourable conditions created as a result of the breeding treatments applied. Agrotechnical treatments clearly increased the disappearance of the PAHs in those soils fertilized with the lowest sewage sludge doses (30 and 75 Mgha(-1)). The results obtained showed that the preferred method of treating a light soil fertilised with sewage sludges should be a one-year system, with a sludge application of 75 Mgha(-1).

Brassica↗
PubMed2005

Genetic diversity of noroviruses in raw and treated sewage water.

Human noroviruses cause gastroenteritis in humans, leading to high virus loads in sewage. Norovirus concentrations in raw and treated sewage samples from two sewage treatment plants (STP) were studied, along with virus removal and genetic diversity. Over one year, the average norovirus concentrations in raw sewage were approximately 10(5) pcr detectable units (pdu) per liter compared with 10(3) pdu/l of treated sewage. Similar sewage treatment processes at STP-A and STP-B led to 2.7 and 2.0 log(10)-units of virus removal, respectively. In total, 11 different norovirus variants were detected in 49 out of 53 sewage samples, with up to four different norovirus strains in a single sewage sample. Along with GGI.6 Sindlesham and GGII.2 Melksham, the GGIIb variant was one of the most prevalent noroviruses in both raw and treated sewage. This strain emerged among populations in Europe in 2000 and 2001. Treated sewage containing 10(2)-10(3) norovirus pdu is discharged into the surface water. The use of such fecally contaminated surface waters for shellfish culture, drinking water production and recreational purposes poses a potential health risk. We showed the presence of multiple norovirus strains in raw and treated sewage, confirming the need to clone before sequencing the RT-PCR products. Exposure to multiple norovirus strains in sewage contaminated food or water may lead to the occurrence of norovirus recombinants, which may be more virulent and pathogenic than the norovirus strains already circulating in the population.

Environmental Monitoring↗
PubMed1997

Land application of sewage sludge in China.

Land application of sewage sludge in China is thoroughly reviewed. Operation of sewage sludge disposal is usually expensive and/or easy to contaminate the environment. In China, most sewage sludge has not been treated and disposed of properly, resulting in environmental pollution and potential exposure to humans. In the near future, sewage sludge production in China will increase rapidly together with the dramatic increase of municipal wastewater treatment ratio (treated/produced), implying that the problem of sewage sludge disposal will become more serious and unavoidable. Proper land utilization of stabilized sewage sludge can make a positive contribution to agriculture, forestry, horticulture and city development. Heavy metals, organic pollutants and pathogens concentrated in sewage sludge during wastewater treatment are the main obstacles to land application of sewage sludge. To promote land application of sewage sludge in China, a statewide survey of sewage sludge production and harmful components in sewage sludge should be carried out. Sewage sludge management and technologies for sludge treatment and disposal suitable to Chinese conditions should be paid more attention.

Agriculture↗
PubMed2006

Critical evaluation of the use of the hydroxyapatite as a stabilizing agent to reduce the mobility of Zn and Ni in sewage sludge amended soils.

The leachability of zinc (Zn) and nickel (Ni) was investigated in various soil types amended with sewage sludge and sewage sludge treated with hydroxyapatite. Sandy, clay and peat soils were investigated. For leachability tests, plastic columns (diameter 9 cm, height 50 cm) were filled with moist samples up to a height of 25 cm. Sewage sludge (1 kg) was mixed with 4.6 kg of clay and sandy soils and with 6.7 kg of peat soil. For sewage sludge mixtures treated with hydroxyapatite, 0.5 kg of the hydroxyapatite was added to 1 kg of the sewage sludge. Neutral (pH 7) and acid precipitation (pH 3.5) were applied. Acid precipitation was prepared from concentrated HNO(3), H(2)SO(4) and fresh doubly distilled water. The amount of precipitation corresponded to the average annual precipitation for the city of Ljubljana, Slovenia. It was divided into eight equal portions and applied sequentially on the top of the columns. The results indicated that the leachabilities of Zn in sewage sludge amended peat and clay soils were low (below 0.3% of total Zn content) and of Ni in sewage sludge amended sandy, clay and peat soil below 1.9% of total Ni content. In sewage sludge amended sandy soil, the leachability of Zn was higher (11% of Zn content). The pH of precipitation had no influence on the leachability of either metal. Treatment of sewage sludge with hydroxyapatite efficiently reduced the leachability of Zn in sewage sludge amended sandy soil (from 11% to 0.2% of total Zn content). In clay and peat sewage sludge amended soils, soil characteristics rather than hydroxyapatite treatment dominate Zn mobility.

Durapatite↗
PubMed2004

The composition and persistence of faecal coliforms and enterococcal populations in sewage treatment plants.

AIMS: The changes in structure and composition of faecal coliforms and enterococcal populations in sewage from different treatment plants, and the elimination of vancomycin- and erythromycin-resistant enterococci (VRE and ERE, respectively) in these treatment plants was analysed to determine any selective reduction. METHODS AND RESULTS: Faecal coliforms, enterococci, VRE, ERE and spores of sulphite-reducing bacteria were enumerated using standard methods. Samples were enriched where necessary in order to isolate antibiotic resistant strains. The structure and composition of these bacterial populations were determined by biochemical fingerprinting and clustering analysis. High diversity and similarity indexes were detected among all the bacterial populations in raw and treated sewage, independently of their origin and the treatment processes employed. Antibiotic resistant strains were detected in all sewage tested and no selective reduction was observed. CONCLUSIONS: The faecal coliforms and enterococci populations did not differ in the sewage samples studied. The vancomycin and erythromycin resistances of the enterococcal populations were similar in the sewage samples. Resistance to both antibiotics persisted after the treatment process independently of raw sewage flow, faecal origin or size of the human population contributing to sewage. However, sewage of mixed origin (human and animal) presented a lower similarity index for the two bacterial populations compared with that of the other human sewage analysed. SIGNIFICANCE AND IMPACT OF THE STUDY: Although a significant reduction in bacterial populations was observed, the persistence of VRE and ERE strains in the same proportions in sewage suggests that there is no selective elimination of bacterial populations during the treatment processes. The ability of antibiotic resistance strains to survive sewage treatment systems should be considered in certain water reuse programmes.

Anti-Bacterial Agents↗
PubMed2001

[Detection of astrovirus RNA from sewage works, seawater and native oysters samples in Chiba City, Japan using reverse transcription-polymerase chain reaction].

Through a year from April, 1999 to March, 2000, 20 samples, which consisted of raw sewage (2), chlorine-treated sewage (2), seawater (10) and naturally grown oysters (6), were collected monthly both from the sewage works at Mihama-ku, Chiba City and at a yacht harbor in Chiba City Bay, Japan. Astrovirus RNA were detected by reverse transcription-polymerase chain reaction (RT-PCR) and was typed by direct sequencing. Astrovirus positive products were detected from 9 samples (raw sewage; 1/2, chlorine-treated sewage; 2/2, seawater; 5/10 and oysters; 1/6) collected in April, 1999. In May, positive products were detected from 4 samples (raw sewage; 2/2 and seawater; 2/10). In June, only 1 positive product was detected from raw sewage. The number of positive samples showed a tendency to decrease and no positive products were detected from samples collected in July, 1999 to January, 2000. After that period, positive products were again detected from 3 samples (raw sewage; 1/2, chlorine-treated sewage; 2/2) collected in February, 2000. In March, the number of positive samples showed the peak and positive products were detected from 12 samples (raw sewage; 2/2, chlorine-treated sewage; 2/2, seawater; 7/10 and oysters: 1/6). Astrovirus positive products detected in April, May, June, July, 1999 and February, 2000 were classified into type 1 or 2 by sequencing, whereas in March, 2000 were type 1, 2, 3, 6 and 7.

Animals↗