Occurrence and distribution of persistent organochlorine compounds in U.K. sewage sludges

A total of 444 sewage sludges, sampled from sewage treatment works in the U.K., were analyzed for polychlorinated biphenyls (PCB) and the organochlorine insecticides γ-Hexachlorocyclohexane (γ-HCH), aldrin, dieldrin and endrin. PCB, γ-HCH and dieldrin were found to occur more frequently and at higher concentrations in sewage sludges than aldrin and endrin. In order to investigate the temporal variation of these compounds in sewage sludge, three sewage treatment works were sampled at monthly intervals over an 18 mo period. PCB, γ-HCH and dieldrin were again the most frequently detected compounds. Concentrations of aldrin and endrin were only sporadically detected. The results of a serial correlation analysis of these data indicated that some short term correlation of PCB and dieldrin concentrations above and below the mean value was evident. The data acquired in the course of this survey have been compared with the results of similar work conducted previously in the U.K. and other countries. The possible implications of the presence of persistent organochlorine compounds in sewage sludges which are disposed to the environment are discussed.     

Particle size fractionation of soil containing coal and combusted particles

Standard procedure for dispersing natural soils for particle size fractionation can be too aggressive for soil containing coal and other organic particles from coal industries. We have investigated ultrasonic dispersion for the latter in four soils differing in pedogenesis (Phaeozem, Podzol, reclaimed mine soils), carbon content (27.5–138.6 g kg^–1), clay content (80–153 g kg^–1) and sources of particles (airborne coal dust, combustion residues, lignite particles). As we found previously for natural soils, the ultrasonic energy needed for complete dispersion varies between 450 and 500 J ml^–1, but the resulting particle size distributions differ from those obtained by standard textural analysis. This is probably related to the different properties of native soil organic matter and coal and combusted particles. Coal and soot particles may partly resist oxidation with hydrogen peroxide, depending on material and particle size. The diameter of lignite particles, remaining after oxidation, is overestimated in sedimentation analysis by a factor of 1.66. Sand-sized lignite particles can be disrupted by ultrasonication and redistributed to finer particle size fractions. The ultrasonic dispersion and particle size fractionation procedure can be applied to soils containing coal and combusted particles, but caution is needed in interpreting the results if they contain large proportions of coal particles.     

Determination of organic matter in sewage sludges

Abstract

Procedures for determining organic matter indirectly and directly in sludges are described. A good agreement between chromic acid oxidation and dry—combustion elemental analysis methods of determining organic‐C was observed. Sludge organic matter content was determined directly by loss‐on‐ignition by thermal analysis. An average C factor of 1.68 to estimate the organic matter from organic‐C, obtained by chromic acid oxidation method, was calculated for aerobically digested sludges.     

Particle size fractionation of fungal and bacterial biomass in subalpine grassland and forest soils

Characterization of soil aggregates according to particle size fractions is a useful tool in process-oriented research into soil organic matter and biological properties. Substrate-induced respiration (SIR) inhibition was used to quantify microbial, fungal and bacterial biomass in particle size fractions of soils ranging from forest to grassland in a subalpine region of central Taiwan. In addition, ergosterol content was determined in the same samples to verify fungal biomass measured by SIR inhibition technique. Surface soil (0–10 cm) was fractionated into four particle size fractions: coarse sand (250–2000 μm), fine sand (53–250 μm), silt (2–53 μm) and clay (0.2–2 μm). The larger sized fractions (>250 μm and 53–250 μm) contained higher levels of fungal ergosterol than the smaller sized ones (2–53 μm and 0.2–2 μm). The largest particle size fraction (250–2000 μm) from all studied habitats showed the highest level of microbial biomass, with no clear trend in microbial biomass level among the other size fractions. SIR-calculated fungal biomass level and ergosterol converted fungal biomass content were positively correlated (r=0.71, p<0.05), and such correlation decreased as biomass levels were high. Ratios of fungi to bacteria ranged between 0.6 and 1.3 in fractions obtained in this study. This study indicates a high variability of microbial (fungal and bacterial) biomass level among particle size fractions in soil, and that the large-sized fractions tend to contain a high level of microbial biomass in a given ecosystem.     

Trace metals and chlorinated hydrocarbons in sewage sludges of Kuwait

Levels of trace metals and chlorinated hydrocarbons were determined in sludge produced at the three main wastewater treatment plants in Kuwait (Ardhiya, Jahra, and Reqqa). Over the 6 mo study period (October 1984 to March 1985) levels at the three plants showed the following ranges (μg g^?1 dry weight); Cd, 0.5 to 5.0; Cu, 90 to 270; Zn, 1100 to 3000; Pb, 80 to 300; Ni, 25 to 60; Hg, 1.8 to 3.6; Ag, 1 to 35; PCBs, 0.1 to 3.6; lindane, 0.4 to 7.4; EDDT (i.e., DDT + DDD + DDE), 0.07 to 0.20; aldrin, below detection to 0.07; endrin, below detection to 0.27; dieldrin, 0.005 to 0.04). Mean levels were generally close or lower than mean concentrations reported in the United Kingdom and the United States. They were also lower than suggested concentration limits for application of sludge on agricultural land, which is one of the most cost-effective and attractive techniques for sludge disposal. For Kuwait to adopt this application, however, the characteristics of the local soil and prevailing environmental conditions, notably the frequent occurrence of severe dust storms, should be considered.     

Concentrations of heavy metals in forty sewage sludges in England

Samples of forty sewage sludges taken in England during 1979 were analysed for ten heavy metals using a rapid flameless atomic absorption spectroscopic technique. For all metals the mean concentrations were influenced by a small number of sludges containing exceptionally high concentrations. Typically, the concentration ranges showed approximately a 100-fold spread. Calculations based on U.K. guidelines for limiting the addition of toxic metals in sludge to agricultural soils indicated that application rates would theoretically be limited for more than 75 % of the sludges by the concentrations of Zn, Cu and Ni, expressed additively as the Zn equivalent. Calculations of the theoretical maximum quantities of sludges which could be applied to land on an annual basis suggested that a significant proportion of the sludges would be unsuitable for application to agricultural land at rates of more than 2 t ha^?1 yr^?1     

Aqueous release of heavy metals from two sewage sludges

Two anaerobically digested sewage sludges, one of relatively low and the other of relatively high heavy metal content, were extracted several times with water to determine the levels of Cu, Zn, and Cd that would be readily available for transport in the soil water if these sludges were applied to land. Generally, the quantity of metal released in the aqueous extracts was between 1 to 7% of the total content with Cu and Zn being released to a greater extent than Cd. The porportion of relatively mobile, non-cationic heavy metals in the aqueous extract differed in the two sludges and ranged from < 1% for Zn and Cd in one sludge to 56.2% for Cd in the other sludge.[/P ]     

Carbon mineralization in an arid soil amended with thermally-dried and composted sewage sludges

Soil amendment with sewage sludge (SS) from municipal wastewater treatment plants is nowadays a common practice for both increasing soil organic matter and nutrient contents and waste disposal. However, the application of organic amendments that are not sufficiently mature and stable may adversely affect soil properties. Composting and thermal drying are treatments designed to minimize these possible deleterious effects and to facilitate the use of SS as a soil organic amendment. In this work, an arid soil either unamended or amended with composted sewage sludge (CSS) or thermally-dried sewage sludge (TSS) was moistened to an equivalent of 60% soil water holding capacity and incubated for 60 days at 28 °C. The C–CO₂ emission from the samples was periodically measured in order to study C mineralization kinetics and evaluate the use of these SS as organic amendments. In all cases, C mineralization decreased after the first day. TSS-amended soil showed significantly higher mineralization rates than unamended and CSS-amended soils during the incubation period. The data of cumulative C–CO₂ released from unamended and SS-amended soils were fitted to six different kinetic models. A two simultaneous reactions model, which considers two organic pools with different degree of biodegradability, was found to be the most appropriate to describe C mineralization kinetics for all the soils. The parameters derived from this model suggested a larger presence of easily biodegradable compounds in TSS-amended soil than in CSS-amended soil, which in turn presented a C mineralization pattern very similar to that of the unamended soil. Furthermore, net mineralization coefficient and complementary mineralization coefficient were calculated from C mineralization data. The largest losses of C were measured for TSS-amended soil probably due to an extended microbial activity. The results obtained thus indicated that CSS is more efficient for increasing total organic C in arid soils.     

Particle size and free iron oxide distribution in some latosols and groundwater laterites of Ghana

The distribution of particle size and Na-dithionite-extractable (di-Fe₂ O₃) and NH₄-oxalate-extractable (ox-Fe₂O₃) iron oxides were investigated in twelve soil profiles representing latosols and groundwater laterites. Soil profiles studied were selected from the major ecological zones of Ghana. The pattern of distribution of free Fe₂O₃ was closely related to that of clay (< 2μ) in soil profiles of the humid forest zones where clay content was more than 40% in the B horizons. In soil profiles of the relatively dry savannah zones with less than 40% clay in the B horizon, the pattern of distribution of free Fe₂O₃ was closely related to that of silt (2–20 μ). The amount of free Fe₂O₃ in the soils appeared to be related to kind of parent rock or parent material and to climatic factors operating in the various ecological zones. Using the amount of di-Fe₂O₃ in the B horizon as a basis for assessing the relative degrees of pedogenesis in soil profiles developed from the same kind of parent material, it was concluded that soil profile development had progressed most in the rain forest zone. Free Fe₂O₃ was considered as having reached an advanced stage of crystallinity or aging in most of the soils because of the low ox-Fe₂O₃/di-Fe₂O₃ ratios in the solums of most of the soil profiles. Soils studied were placed in the ferrallitic and ferruginous soil classes of D'Hoore. The great soil groups could not be characterized by depth function curves of free Fe₂O₃. However, it was proposed that the relative amounts of di-Fe₂O₃ in the B horizons of the soil profiles could be used as a basis for classifying these soils at the family level.     

Determination of heavy metals in municipal sewage plant sludges by neutron activation analysis

Research is presented which deals with the use of Neutron Activation Analysis (NAA) to scan sewage sludges for their trace metal content. Of special interest are the metals Hg, Se, Cr, Sb, Co and Fe which are highlighted in sludges from six North Carolina cities that represent the spectrum of rural to heavily industrialized pollution sources. Trace metal content variations and possible meanings for these variations are presented along with the precision and potential of NAA for trace metal scanning.     

Particle size distribution of orange juice cloud after addition of sensitized pectin

The effect of the addition of commercial pectin to orange juice that was de-esterified by alkaline treatment or pectinmethylesterase was evaluated. Pectin at various degrees of esterification (DE) was added to reconstituted frozen orange juice concentrate, and the extent of cloud loss was determined after centrifugation. Of the five pectin treatments, percent transmittance (% T) of juice remained <5%, except for the pectin treatment with a residual methoxyl content (% DE) of <5%. Addition of 100--600 ppm of 5% DE pectin to juice resulted in % T between 36 and 73%. Despite the absence of clarification, increases in cloud particle size were observed and depended on the % DE, the amount of pectin added, and the method used to modify the pectins.     

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。     

Total concentrations of heavy metals and occurrence of antibiotics in sewage sludges from cities throughout China

Purpose

A total of 58 dewatered sludge samples were collected from 58 sewage treatment plants (STPs) geographically located in 31 provincial cities of China; the concentrations of heavy metals and antibiotics were determined to monitor the pollutant levels on a large scale, and the pollutant concentrations in sludge samples from different sources of sewage sludge and different geographical regions were compared.

Materials and methods

All the samples were divided into two portions, one of which was air-dried for determination of heavy metals. The other portion was placed in a brown glass bottle and frozen at ?20 °C for antibiotics analysis. Total heavy metals were digested with aqua regia and determined by atomic absorption spectrophotometry (Varian SpectrAA 220FS and Varian SpectrAA 220Z). The antibiotics were extracted with EDTA-sodium phosphate buffer with acetonitrile/Mg(NO₃)₂-NH₃?H₂O, v/v, 3:1 and analysed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) and quantified by the isotope-labelled internal standard method.

Results and discussion

In all the sludge samples, zinc was the most abundant metal followed by copper, with relatively low concentrations of chromium, lead, nickel and cadmium. Only 20 % of samples exceeded the Chinese class A values of heavy metal standards for agricultural use (GJ/T309-2009). Sixteen different antibiotics were detected in all the sludge samples, and fluoroquinolones (FQs) and tetracyclines (TCs) were more abundant than sulfonamides (SAs). Concentrations of ∑FQs, ∑TCs and ∑SAs ranged from 1,569 to 23,825 μg kg^?1 (mean 8,274 μg kg^?1, dry weight), from 592 to 37,895 μg kg^?1 (mean 8,326 μg kg^?1, dry weight) and from 20.1 to 117 μg kg^?1 (mean 55.4 μg kg^?1, dry weight), respectively. Tetracyclines (except chlortetracycline) were significantly correlated with zinc and lead. No significant regional trends were observed in the concentrations of heavy metals and antibiotics in sludges.

Conclusions

Heavy metal concentrations are not the major factor restricting domestic and mixed flow sludge application, but the antibiotic concentrations in sludges are problematic; regulation of antibiotic use and establishment of standards to ensure safe handling of sludges are needed.     

污泥堆肥和热干燥对土壤和土壤腐殖酸性质的影响

The effect of annual additions of composted sewage sludge (CS) and thermally dried sewage sludge (TS) at 80 t ha^-1 on soil chemical properties was investigated for three years in a field experiment under semiarid conditions. Humic acids (HAs) isolated by conventional procedures from CS, TS, and unamended (SO) and sludge amended soils were analysed for elemental (C, H, N, S and O) and acidic functional groups (carboxylic and phenolic) and by ultraviolet-visible, Fourier transform infrared and fluorescence spectroscopies. With respect to CS, TS had similar pH and total P and K contents, larger dry matter, total organic C, total N and C/N ratio and smaller ash content and electrical conductivity. Amendment with both CS and TS induced a number of modifications in soil properties, including an increase of pH, electrical conductivity, total organic C, total N, and available P. The CS-HA had greater O, total acidity, carboxyl, and phenolic OH group contents and smaller C and H contents than TS-HA. The CS-HA and TS-HA had larger N and S contents, smaller C, O and acidic functional group contents, and lower aromatic polycondensation and humification degrees than SO-HA. Amended soil-HAs showed C, H, N and S contents larger than SO-HA, suggesting that sludge HAs were partially incorporated into soil HAs. These effects were more evident with increasing number of sludge applications.     

Application of composted sewage sludges contaminated with heavy metals to an agricultural soil

To elucidate the mechanism of transfer of heavy metals into the food chain, an experiment was carried out with a calcareous soil, to which two different doses of a sewage sludge compost contaminated with either Cd or Zn, Cd, Cu, and Ni were applied. A crop of lettuce was then grown in the amended soils. The application of sewage sludge composts to a calcareous soil lowered the soil's pH, although the value was always around 8 at the end of the experiment. Electric conductivity rose with organic amendment. As anticipated, such an amendment improved the nutritional level of the soils, particularly Nand P, both total and available. Plant yields were negatively affected by organic amendments contaminated with heavy metals, the most dangerous in our experiment being Cd and Zn since this metals easily taken up by plants. As Ni and Cu form insoluble complexes with the organic matter of the sewage sludge composts they are not readily absorbed. Of the metals studied, Cd and Zn showed the highest bioavailability index.     

花岗岩风化产物中高岭石和埃洛石的粒径分布及其对土壤发生的意义

The kaolins collected from a profile of weathered granite at Yichun County, Jiangxi Province have been subjected to particle size fractionation by the conventional sedimentation method and examined by XRD, SEM and TEM. All of them exhibit a mixture phase of poorly crystallized kaolinites and halloysites (0.7 nm) occurring as the main clay minerals. Electron micrographs reveal that plate kaolinites are the principal constitution in the coarse fraction, and more tubular and curled halloysite (0.7 nm) in the fine fraction. Both of them show normal probability curves in particle size distributions. The ratios of kaolinite and halloysite (0.7 nm) in different size fractions are examined by X-ray diffraction with a series of X-ray patterns characterized by three main peaks at d(001), d(002) and d(020),varying in intensity. Therefore, an index Q_hm expressed as (I_d(001) + I_d(002))/(2×I_d(002)), is designed to indicate relative ratios of the two clay minerals in a number of mixture phases. Because kaolinite and halloysite (0.7 nm) commonly occurred, respectively, in low and medium leaching microenvironment, the index Q_hm, can be used to indicate weathering and pedogenic conditions of a weathering crust.     

The analysis of PAHs nitrogen derivatives in the sewage sludges of upper Silesia, Poland

The dimethylformamide extracts from sewage sludges from a chosen sewage — treatment plant in highly industrialized region of Poland were investigated. Using the column chromatography with Al₂O₃ and silicic acid as the stationary phases, the fraction of azaarenes has been separated. GC-MS analysis of azaarenes fraction made it possible to identify 10 azaarenes and several of their alkyl derivatives, which dominate in the organic matter extracted from sewage sludges. The silicic acid column chromatography in connection with the reduction of nitroarenes and derivatization with pentafluoropropionic acid anhydride yielded an enriched nitrofraction. Nitroarenes present in this fraction as amide derivatives were also analysed by GGMS method. There was found presence of 3 nitroarenes and their methyl derivatives.     

中国五个典型城市污水厂污泥中重金属的形态分布研究

Metal content and bioavailability are often the limiting factors for application of sewage sludge in agricultural fields. Sewage sludge samples were collected from five typical urban wastewater treatment plants in China to investigate their contents and distribution of various chemical fractions of Cu, Zn, Ni, Cr, Pb and Mo by using the BCR （Community Bureau of Reference） sequential extraction procedure. The sludges contained considerable amounts of organic matter （31.8%- 48.0%）, total N （16.3-26.4 g kg^-1） and total P （15.1-23.9 g kg^-1）, indicating high potential agricultural benefits of their practical applications. However, total Zn and Ni contents in the sludge exceeded the values permitted in China＇s control standards for pollutants in sludges from agricultural use （GB 4284-1984）. The residual fraction was the predominant fraction for Mo, Ni and Cr, the oxidizable fraction was the primary fraction for Cu and Pb, and the exchangeable and reducible fractions were principal for Zn. The distribution of different chemical fractions among the sludge samples refiected differences in their physicochemical properties, especially pH. The sludge pH was negatively correlated with the percentages of reducible fraction of Cu and exchangeable fraction of Zn. The sludges from these plants might not be suitable for agricultural applications due to their high contents of Zn, Ni and Cr, as well as high potential of mobility and bioavailability of Zn.     

Trace metal analysis of sewage sludge and soils in Bahrain

Trace metals such as Pb, Zn, Cu, Ni, Cd and Fe were determined in sewage sludge produced at a sewage treatment plant in Bahrain (Tubli) and soils. The soils, both untreated and treated with the sludge, are used for agricultural purposes in Bahrain. The Trace-metals level showed the following range (μg g^?1 dry weight); Pb, 242 to 609; Zn, 704 to 836, Cu, 329 to 512; Ni, 23 to 41; Cd, 1.8 to 3.9 and Fe, 1867 to 4284. The data show the degree to which untreated soils have already been contaminated with trace elements. The level of trace-elements found in sludge showed the following range (μg g^?1 dry weight); Pb, 140 to 186; Zn, 597 to 836; Cu, 348 to 449; Ni, 47 to 53; Cd 5.7 to 9.2 and Fe, 5950 to 8520. Mean levels were generally close or lower than mean concentration reported in the United Kingdom and the United States for sludge. They were also lower than the suggested concentration limits for application of sludge on agricultural land, which is one of the most cost effective and attractive techniques for sludge disposal. Soils treated with this sludge (after 1 yr) were also analyzed and showed substantial enhancement of the available level of trace elements in the soil. This eventually will lead to an increase in the trace-element level in plants grown for human or animal consumption. This could have phytotoxic effects, and the possibility of toxic effects on live-stocks and human beings.