Rates Of Sewage Sludge Research Articles

Comparação entre dois correctivos orgânicos quanto à disponibilidade do fósforo para o azevém

Municipal solid waste compost (MSW) and urban sewage sludge (SS) applied to soils, containing phosphorus (P) in organic and inorganic forms, can affect the element dynamics in soil, with subsequent reflexes on plant nutrition. This work aimed to evaluate the effects of the application of a MSW and a biologically treated SS on P uptake by a test plant and soil “available” P concentration as determined by the Egner-Riehm method (Riehm-P). The study fell upon soil and plant samples deriving from a pot trial with multiple aims. It had two pot series, one maintained with annual ryegrass (Lolium multiflorum) during approximately seven months, and the other one without plants until the end of the same period. The treatments of each series, in triplicate, referring to the combinations of two soils and four MSW and SS rates (equivalent to 0, 15, 30, and 60 t/ha) were compared. Topsoil samples of a Haplic Podzol (PZha) and of a Calcic Vertisol (VRcc), with low Riehm-P concentrations, were used. A basal fertilisation including P was applied at the beginning of the trial, in the series cropped with annual ryegrass. Total P uptake, evaluated in six harvests of the aboveground biomass, and soil Riehm-P contents at the last harvest were determined. A single P sorption index (Bache & Williams, 1971) was also determined to compare the initial soils P sorption capacity. The highest total P uptake value (378 mg/pot) was achieved in the VRcc soil at the 60 t/ha SS rate (P ? 0.001). In this soil, total P uptake increased with the MSW and SS application, with the exception of the 15 t/ha MSW rate. However, soil Riehm-P concentration only raised at the 60 t/ha SS rate, in the series without plant test, and at the 60 t/ha MSW rate, in the series with annual ryegrass. Differently, in the PZha soil, total P uptake values were not higher than the control but at the highest MSW and SS rate, where they did not differ (P? 0.001). This agreed to the much higher positive effect of the same MSW and SS rate on soil Riehm-P concentration, in both series. The highest SS rate was as or more efficient than the same MSW rate in increasing P availability in these soils, in part due to its higher total P content. Other specific soil P studies will help to clarify the different soil behaviour, namely the soil pH evolution and P sorption capacity variation as influenced by the residue application.

Mineral concentrations in herbage and soil in a Pinus radiata silvopastoral system in north‐west Spain after sewage sludge and lime application

SummarySilvopastoral systems in north‐west Spain can reduce the risk of fires and promote multi‐purpose forest land use. Fertilizer application is important for optimal pasture and tree production. The application rate of sewage sludge as a fertilizer is regulated and is based on its nutrient concentration, especially nitrogen. The aim of this study was to assess the effect of three consecutive years of application of different application rates of sewage sludge and inorganic fertilizer, with or without lime (2·5 t CaCO3 ha−1) on the ammonium, nitrate and exchangeable K, Ca and Mg contents in soil, and on the crude protein (CP), K, Ca and Mg concentrations in herbage in a silvopastoral system established under a 5‐year‐old Pinus radiata D. Don plantation with a density of 1667 trees ha−1. The experiment was started in autumn 1997, when a pasture mixture was sown (25 kg ha−1Lolium perenne, 10 kg ha−1Dactylis glomerata and 4 kg ha−1Trifolium repens). Changes in ammonium and nitrate content in the soil in response to liming and sewage sludge application reflected the initial pH of the soil. In general, liming increased the available Ca and Mg content in soil, and CP and Ca concentrations in herbage, but reduced exchangeable K content in the soil in the first year. Application of sewage sludge increased all of the measured nutrients in both soil and herbage.

Polycyclic aromatic hydrocarbons and phthalic acid esters in the soil–radish ( Raphanus sativus) system with sewage sludge and compost application

We studied the accumulation of polycyclic aromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs) in a latosolic red soil and radish ( Raphanus sativus) with application of sewage sludge at rates of 10, 20 and 40 g kg −1 soil or compost at rate of 10 g kg −1 soil. In radish the concentrations of individual PAHs and PAEs varied from non-detectable to 803 μg kg −1 dry weight (d.w.) and from non-detectable to 2048 μg kg −1 d.w., respectively. Compared to the control, higher application rates of sewage sludge resulted in pronounced increases in shoot, root and soil concentrations of PAHs and PAEs. PAE concentrations in radish grown in soil spiked with sludge compost were higher while the PAH concentrations were comparable to those receiving 10 g kg −1 of sewage sludge. However, the root biomass of radish in soil amended with compost was significantly higher and the shoot-to-root ratio was significantly lower than in the other treatments. The bioconcentration factors (BCFs, the ratio of contaminant concentration in plant tissue to the soil concentration) of di- n-butyl phthalate and di(2-ethylhexyl) phthalate in both shoots and roots and of total PAH concentrations in roots were less than 1.0, but some BCFs for individual PAHs were high with a maximum value of 80.

ALGODOEIRO CULTIVADO EM SOLO TRATADO COM CALCÁRIO, LODO DE ESGOTO E CÁDMIO

Key words: Gossypium hirsutum, biosolid, liming, trace elements, organic residue.ABSTRACTThe objective of the work was to evaluate the accumulation of nutrients and heavy metals in different parts of the cotton plants (Gossypium hirsutum cv. IAC 22) cultivated in soil that received lime and sewage sludge from municipal treatment plant plus cadmium. The experiment was carried out under green house conditions. The soil was a Clayey Red Latosol (Oxisol). The experimental design was the randomized blocks. The treatments were organized in a 3x2+1 factorial scheme (three lime rates, two sewage sludge rates and a Control treatment), all with three replications. The variance test was made by F test and means comparisons by Tukey test (p< 0.05). The different lime rates provided larger macronutrientes accumulations in the shoot and micronutrients in the roots. The sewage sludge addition provided the macronutrients accumulation, especially, in the roots and shoot of the plants, and of Mn and Zn in the root and shoot and just Mn in the fibers. The Fe accumulation in the roots decreased with the application of the sewage sludge. The liming and the sewage sludge provided accumulation of Pb in the roots, shoot and fibers. When it was just considered the liming, similar effect was found for the Cd and Ni in the fibers.Palavras-chave: Gossypium hirsutum, biossolido, calagem, elementos traco, residuo orgânico

Nickel in a tropical soil treated with sewage sludge and cropped with maize in a long-term field study

Sewage sludge produced by the SABESP wastewater treatment plant (Companhia de Saneamento Básico do Estado de São Paulo), located in Barueri, SP, Brazil, may contain high contents of nickel (Ni), increasing the risk of application to agricultural soils. An experiment was carried out under field conditions in Jaboticabal, SP, Brazil, with the objective of evaluating the effects on soil properties and on maize plants of increasing rates of a sewage sludge rich in Ni that had been applied for 6 consecutive years. The experiment was located on a Typic Haplorthox soil, using an experimental design of randomized blocks with four treatments (rates of sewage sludge) and five replications. At the end of the experiment the accumulated amounts of sewage sludge applied were 0.0, 30.0, 60.0 and 67.5 t ha −1. Maize ( Zea mays L.) was the test plant. Soil samples were collected 60 d after sowing at depths of 0–20 cm for Ni studies and from 0 to 10 cm and from 10 to 20 cm for urease studies. Sewage sludge did not cause toxicity or micronutrient deficiencies to maize plants and increased grain production. Soil Ni appeared to be associated with the most stable fractions of the soil organic matter and was protected against strong extracting solutions such as concentrated and hot HNO 3 and HCl. Ni added to the soil by sewage sludge increased the metal concentration in the shoots, but not in the grain. The Mehlich 3 extractor was not efficient to evaluate Ni phytoavailability to maize plants. Soil urease activity was increased by sewage sludge only in the layer where the residue was applied.

ASSESSMENT OF MINED SOILS IN EROSION-DEGRADED FARMLANDS IN SOUTH-EASTERN NIGERIA

This study assessed degradation status of erosion devastated soils as well as ameliorative measures on such soils. Field sampling was aided by morphological landscape changes. Surface samples (0-20 cm) depth were randomly collected from two erosion units and used in conducting a greenhouse experiment using maize (Zea mays L.) as a test crop. The experiment was laid out in a completely randomized design (CRD) and rates of ground periwinkle shells (GPS) and sewage sludge (SS) used as treatment. Treatments were replicated 9 times. Statistical tests of difference in soil properties were performed using t-statistic at p &lt; 0.05. Status of soil degradation was evaluated using Land Degradation Index (LDI). Results showed low organic carbon content, and high bulk density and aggregate instability in eroded soils. The LDI values were high in most of physical parameters. The GPS and SS treatments significantly (p &lt; 0.05) improved yield and soil properties except soil pH and aluminium saturation.

BASIC STUDY OF CONCRETE MADE USING ASH DERIVED FROM THE INCINERATING SEWAGE SLUDGE

Sewage sludge incinerated ash is discharged as waste. Those are increasing with progress of a sewage enterprise every year. However, the reservation of the last disposal place for reclaiming the generated incineration ash is becoming quickly difficult. In this situation of sewage sludge processing, it is very important to promote more reducing and development of new reusing method. Recently, in the construction industry, reusing technology that was used sewage sludge incinerated ash as aggregate for concrete products is developed. But there are many unknown points in the performance and durability of concrete. In this study, sewage sludge incinerated ash is used instead of natural aggregate for concrete. It is investigated about fresh characteristics, chloride content, strength, resistance to frost damage and drying shrinkage of concrete using sewage sludge incinerated ash. As the results of this research, the compressive strength increases with ratio of sewage sludge incinerated ash. And the relationship between the compressive strength and the dynamic modulus of elasticity can be comparatively expressed as the linear relationship. If this concrete includes proper air content, the resistance to frost damage is enough. The drying shrinkage is become larger with increase of substitute rate of sewage sludge incinerated ash.

The use of compost in afforestation of Mediterranean areas: Effects on soil properties and young tree seedlings

In Mediterranean frequently burnt areas, fire and erosion result in the decrease of soil fertility, so afforestation is a major concern. We carried out an in situ experiment of compost amendment to improve survival and growth of planted tree seedlings. One-year-tree seedlings of native species (Quercus ilex, Pinus halepensis and Pinus pinea) were planted on a frequently burnt calcareous site. Three rates of fresh co-composted sewage sludge and greenwastes (control without compost, 20 and 40 kg m−2 of compost) were incorporated into the soil at each seedling stem. Changes of soil properties and tree development were studied during 3 years (2001–2003) and 2 years (2002–2003) respectively.The compost improved survival of Quercus ilex and Pinus pinea seedlings in severe drought conditions, but had no effect on Pinus halepensis. For all species seedling length and radial growth and NPK nutrition were increased for both rates of amendment. Amendment improved soil fertility, but available P concentration increased 13 fold in the neighbouring soil of seedlings amended at the maximal rate compared to control. However, amendment did not significantly increase concentrations of Cd, Cr, Ni and Pb in soils or tree seedlings. It increased Cu and Zn total and available concentrations in soils, while foliar Cu and Zn concentrations in the seedlings remained similar in all plots.Compost can efficiently help afforestation of dry soils with low organic matter content. However, sewage sludge concentrations in P, and to a lesser extent in Cu and Zn, limit rates of application that can be applied without environmental hazard.

Nitrogen transformation from three soil organic amendments in a sandy soil

A sandy soil was amended with various rates (20 – 320 g air-dry weight basis of the amendments per kg of air-dry soil) of chicken manure (CM), sewage sludge (SS), and incinerated sewage sludge (ISS) and incubated for 100 days in a greenhouse at 15% (wt/wt) soil water content. At the beginning of incubation, NH4-N concentrations varied from 50 – 280 mg kg−1 in the CM amended soil with negligible amounts of NO3-N. Subsequently, the concentration of NH4-N decreased while that of NO3-N increased rapidly. In soil amended with SS at 20 – 80 g kg−1 rates, the NO3-N concentration increased sharply during the first 20 days, followed by a slow rate of increase over the rest of the incubation period. However, at a 160 g kg−1 SS rate, there were three distinct phases of NO3-N release which lasted for160 days. In the ISS amended soil, the nitrification process was completed during the initial 30 days, and the concentrations of NH4-N and NO3-N were lower than those for the other treatments. The mineralized N across different rates accounted for 20 – 36%, 16 – 40%, and 26 – 50% of the total N applied as CM, SS, and ISS, respectively.

Effect of sewage sludge on microbial biomass, basal respiration, metabolic quotient and soil enzymatic activity

Monitoring soil quality by means of biological indices can be of help for the management and sustainability of soils that received sewage sludge application. The objective of this study was to evaluate the effect of long-term and continued application of sewage sludge rates on microbial biomass, basal respiration, metabolic quotient and enzymatic activity of a Dark Red Dystroferric Latosol under field conditions in the tropical region. To that effect, four applications of sewage sludge from an industrialized region were performed on a Dark Red Dystroferric Latosol. Sludge was incorporated to the soil at concentrations of 0, 1, 2, 4 and 8 times the recommended rate based on their nitrogen content in four consecutive corn cultivations. The results showed that basal respiration, the C and N microbial biomass, metabolic quotient (qCO 2) and enzymatic activity in the soil increased as sewage sludge was added, and their values were positively correlated with sewage sludge doses. The activities of soil urease and amylase increased as sludge doses increased and were significantly correlated with soil microbial biomass. These results suggest that the amount of sewage sludge applied has to be calculated based on the N crop needs, and annual applications must be avoided to prevent over-applications.

Use of Composted Sewage Sludge as Horticultural Growth Media: Effects on Germination and Trace Element Extraction

The increasing demand for growth media for greenhouse horticultural uses, the rising new uses of substrates, and the scarcity and cost of traditional sources, such as sphagnum peat moss in Mediterranean countries, have focused research on new substrate materials. Use of composted sewage sludges as a component of growth media could be a feasible alternative, with the benefit of their high availability and their very low cost. In this study, the effects of composted sewage sludge, blended with sphagnum peat moss in growth media, on germination and trace element extraction of cauliflower (Brassica oleracea var italica Plenc cv. Tenere), broccoli (Brassica oleracea var. Botryti cv. Marathon), and lettuce (Lactuca sativa c.v. Malta) were studied. Four treatments were established, on the basis of the addition of increasing quantities of composted sewage sludge to peat (0, 15, 30, and 50%, v/v). Germination percentage and trace elements (Fe, Cu, Mn, Zn, B, Pb, Ni, Cd, and Cr) extraction and differential root/aerial part distribution were studied. Increasing sewage sludge treatments (especially 30 and 50%) reduced germination of lettuce and broccoli. In cauliflower seedlings, an increment of germination was observed for the 15 and 30% treatments compared with the control. The contents of Fe, Cu, Mn, and Zn in plant tissues increased with the increasing rate of sewage sludge in the media. The highest micronutrient extraction efficiency was observed in broccoli (roots) and lettuce (leaves). Fe and Zn were the micronutrients extracted to a higher degree in all plants. Mn was mainly accumulated in aerial parts. Heavy metal extraction was very low in relation to micronutrients. Cd, Pb, and Cr were mainly accumulated in roots and Ni in the aerial parts.

Growth, yield and solute content of barley in soils treated with sewage sludge under semiarid Mediterranean conditions

Agricultural soils from many parts of the Mediterranean region are subjected to progressive degradation. Application of sewage sludge provides not only a means for its disposal but also improves soil fertility and physical properties, causing an increase in crop yield. A field experiment was carried out from 1998 to 2001, to investigate the effects of sewage sludge application to barley ( Hordeum vulgare L.) var. Sunrise crops on the relationships between plant physiology and some soil properties. Treatments were: (1) fertilization with a conventional inorganic fertiliser (M); (2) 15 t ha −1 of sludge in 1998 only (RS); (3) cumulative sewage sludge application, i.e., repeated applications of 15 t ha −1 every year (CS); and (4) unamended soil as control (C). Cumulative application of sewage sludge to barley crop increased grain yield significantly, which might be associated with improved early establishment of seedlings. The plants had higher dry matter yields and leaf protein concentrations from the beginning of development to ear emergence. These CS plots had lower pH, and increased total organic C (TOC), cation exchange capacity (CEC) and DTPA-extractable heavy metals. This treatment also improved soil microbiological properties, such as basal respiration, microbial biomass and some soil enzyme activities (urease, BAA-protease, phosphatase and β-glucosidase), which promote the recycling of nutrients for crop. Sewage sludge had a positive but short residual effect after only 1-year application. Results indicate that relatively low application rates of sewage sludge could be used for several years to maintain crop production in Mediterranean-type climates. However, there was a significant increase of grain heavy metal concentrations that must be taken into consideration under long-term applications of sludge.

Cumulative and Residual Effects of Repeated Sewage Sludge Applications: Forage Productivity and Soil Quality Implications in South Florida, USA (9 pp)

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 notatum Flugge) 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.

Sewage sludge effects on gas fluxes at the soil–atmosphere interface, on soil δ13C and on total soil carbon and nitrogen

The objective of this work was to study the effect of long-term and continued application of sewage sludge on total carbon and nitrogen, soil δ 13C and on the gas fluxes at the soil–atmosphere interface under field conditions in the tropical region. To that effect, four applications of sewage sludge from an industrialized region were performed on a Dark Red Dystroferric Latosol. Sludge was incorporated to the soil at concentrations of 0, 1, 2, 4 and 8 times the recommended rate based on their nitrogen content in four consecutive corn cultivations. All sludge rates increased the concentration of soil C and N as compared to the control. The soil C contents at the highest sewage sludge rate increased by 55% and 48% at the layers from 0 to 10 cm and from 10 to 20 cm, respectively, as compared to the control. In the case of soil N, the increase was in the order of 59% and 66% at the highest sludge rate at the layers from 0 to 10 cm and from 10 to 20 cm, respectively, relative to the control. The increase in soil C content was derived from the sewage sludge, as demonstrated by δ 13C analyses and, since the soil's δ 13C contents were negative, it is suggested that the soil is sequestering carbon contained in the sewage sludge. The application of sewage sludge increased the flux of CO 2, N 2O and CH 4 to the atmosphere, by 220%, 320% and 165% respectively, for the highest sewage sludge rate, when compared to the control. Even though greater emission of gases was observed as compared to the control and to the treatment corresponding to the crop's recommended mineral fertilization, it is important to note that part of the C added via sewage sludge is becoming sequestered in the soil.

Metais pesados do solo após aplicação de biossólido: I - Fracionamento

Foi realizado experimento em casa de vegetação da FCAV-UNESP, Campus de Jaboticabal, com o objetivo de estudar o efeito do pH e da aplicação de biossólido sobre a distribuição de Cu, Mn, Ni, Pb e Zn nas frações: trocável, orgânica, de óxidos de Fe e Al não-cristalinos, óxidos de Fe e Al cristalinos e residual de dois solos (Neossolo Quartzarênico órtico típico - RQ e Latossolo Vermelho eutroférrico argiloso - LV), coletados da camada arável do terreno, e relacionar esses teores dos metais nas frações com aqueles extraídos pelas soluções de DTPA, HCl 0,1 mol L-1, Mehlich-1 e Mehlich-3 e acumuladas na parte aérea de plantas de milho (Zea mays L.). O delineamento experimental utilizado foi inteiramente casualizado, com três repetições, segundo o esquema fatorial 2 × 2 × 5 (dois solos, presença ou ausência de corretivos e cinco doses de biossólido). Nos tratamentos com calagem, foram adicionados materiais corretivos para elevar o pH(CaCl2) do solo a 5,3. As doses de biossólido utilizadas foram de 0; 13; 26; 52 e 78 g vaso-1 (equivalentes a 0; 10; 20; 40 e 60 t ha-1), com base no material seco. O estudo de fracionamento dos metais mostrou que a maior parte dos metais encontrava-se nas frações com ligações mais estáveis (ligados a óxidos e residual), tendo as frações (trocável e orgânica) apresentado menor representatividade, em relação ao total encontrado. No solo arenoso (RQ), maiores proporções dos metais foram encontradas nas frações mais fitodisponíveis (trocável e orgânica), quando comparado ao solo argiloso (LV). A elevação do pH do solo provocou a redistribuição dos metais da forma trocável para a orgânica e, ou, de óxidos. Por meio de ajustes de regressões múltiplas, verificou-se que as frações, trocável e orgânica, foram as maiores responsáveis pelos teores dos metais extraídos do solo pelas soluções de DTPA, HCl 0,1 mol L-1, Mehlich-1 e Mehlich-3 e pelo acumulado na parte aérea do milho.

Effects of Sewage Sludge Compost on Volatile Organic Compounds of Wine fromVitis viniferacv. Red Grenache

The effect of one application of sewage sludge compost at three rates on the volatile organic compound (VOC) composition of <i>Vitis vinifera</i> cv. Red Grenache wines of two vintages (1999 and 2000) was investigated. After analyzing the 12 major VOC by gas chromatography (GC) and GC/mass spectrometry, results showed significant differences in wine VOC concentrations among the treatments. The first year, application of high rates of sewage sludge compost decreased the total VOC concentrations of wines, especially concentrations of ethyl acetate, ethyl hexanoate, 3-methylbutyl acetate, and ethyl 3-methylbutanoate, which contribute to wine quality. The second year, organoleptic qualities were only slightly distinguished in wines from the different treatments.

Peanut Yield Response to Poultry Litter and Municipal Sludge Application

The use of poultry litter and sewage sludge as a nutrient source continues to increase. The purpose of this study was to evaluate the use of these organic by-products as a source of nutrients for peanut (Arachis hypogaea L.) production. From 1995 to 1998 poultry litter was applied on 13 on-farm sites and composted municipal sludge was used in three of these on-farm experiments. Fertilizer was also applied in all experiments. Rates of poultry litter ranged from 1.9 to 7.2 Mg ha−1. Composted sewage sludge rate was 2.0, 4.0, and 8.1 Mg ha−1. Commercial fertilizer was mixed and applied mixed together at 180, 40, and 111 kg ha−1 for nitrogen (N), P2O5 and K2O, respectively. Phosphorus (P) and potassium (K) were also supplied separately at a rate of 40 and 111 kg ha−1, respectively. Seven of 13 sites had increased yield as a result of poultry litter. Fertilizer increased yield in only two experiments. Sludge increased yield in only one experiment and only the highest rate. At one site, poultry litter gave a greater yield than fertilizer when both increased yield above the control. Treatments did not influence total sound mature kernels percentage (TSMK).

Influence of Sewage Sludge Application on Soil Nitrate Distribution in a Clay Soil

Nitrate contamination in the aquatic systems is the primary indicator of poor agricultural management. The influence of sewage sludge application rates (0, 10, 25, 50 and 100 dry Mg/ha) on distribution of nitrate originating from the sewage sludge in soil profiles was investigated. Soil profile monitoring of nitrate was carried out with a Lakeland clay soil in 1997. Irrespectively of the sewage sludge application rates up to 50 dry Mg/ha, the concentration of <TEX>$NO_3$</TEX>-N at the 120 cm depth was below 10 mg/kg and the difference due to the amount of sewage sludge application was negligible at this depth. There was virtually no <TEX>$NO_3$</TEX>-N below 120 cm depth and this was confirmed by a deep sampling up to 300 cm depth. Most of the nitrate remained in the surface 60 cm of the soil. Below 120 cm depth nitrate concentration was very low because of the denitrification even at high sewage sludge rate of 100 dry Mg/ha. The <TEX>$NO_3$</TEX>-N concentrations in the soil fluctuated over the growing season due to plant uptake and denitrification. The risk of groundwater contamination by nitrate from sewage sludge application up to high rate of 100 dry Mg/ha was very low in a wheat grown clay soil with high water table ( < 3 m).

Nitrogen fertilizer replacement value of sewage sludge, composted household waste and farmyard manure

Field experiments were undertaken during 1998–2000 at Askov Experimental Station and Lundgård Experimental Site, Denmark, to investigate the fertilizer value of anaerobic and aerobic sewage sludges (SS1 and SS2), composted household waste (Compost) and farmyard manure (FYM). The organic residues were applied at two rates with or without supplementary mineral nitrogen (N). The effects of residue application on spring cereal dry matter (DM) yield and N-offtake were related to reference treatments with increasing rates of calcium ammonium nitrate (CAN). DM yields at the high application rates of aerobic sewage sludge (198 kg N/ha/year) and farmyard manure (300 kg N/ha/year) were comparable to the reference treatments receiving 90 kg mineral-N/ha/year. The comparable high application rate of anaerobic sewage sludge was 138 kg N/ha/year only and the DM yield was less. In contrast, the yield effect of Compost was very poor; even the high application rate of 321 kg N/ha/year yielded less than the low application rates of aerobic sewage sludge and farmyard manure, 66 and 100 kg N/ha/year, respectively.The nitrogen fertilizer replacement value (NFRV) of the organic residues was estimated for all four combinations of the response variables DM-yield and N-offtake and the independent variables of total-N and ammonium-N applied. NFRV was in the range 49–68% for the sewage sludges and FYM based on the DM-yield[ratio ]total-N relation, and slightly smaller for the N-offtake[ratio ]total-N relation, 29–53%. The highest values were obtained for the aerobic sewage sludge, having a potential manurial value comparable to FYM. In contrast, the NFRV of Compost was low, about 10%.The concentration of ammonium-N in organic residues and manures is often used for predicting the fertilizer value. Ammonium-N based NFRV of 160–210% for the sewage sludges indicate that water extractable ammonium-N underestimates the NFRV, probably due to the content of easily degradable organic matter in digested sewage sludge. The estimated NFRV for Compost was above 100% but connected with high uncertainty. In contrast, the ammonium-N based NFRV for FYM was only 70–87%, probably due to ammonia volatilization caused by incomplete incorporation of large quantities and the high ammonium-N[ratio ]total-N ratio in this residue.

Assessing the feasibility of land application of fly ash, sewage sludge and their mixtures

Land disposal of fly ash (FA) and sewage sludge (SS) is a major problem due largely to their potentially harmful constituents. Combined use of FA and SS however may help reduce the associated pollution potential. In this paper we summarize the results of several case studies designed to assess the feasibility of land application of FA with and without SS. A wide range of application rates was tested under laboratory, greenhouse and field conditions. The leaching of metals from soil columns amended with moderate rates of FA applications (8–16 Mg ha −1) generally had no significant impact on the metal content of leachate or their downward migration in the soil. The application of FA or SS at a much high rate (74.1 Mg ha −1) significantly increased both leaching and downward migration of metals. The use of 1:1 FA+SS mixture at 148.2 Mg ha −1 reduced metal leaching compared to the combined metal quantities leached when FA or SS applied at 74.1 Mg ha −1. The results indicate that combined use of FA and SS at a rational rate of application should not cause any significant effect on drainage water quality. Plant studies conducted using FA and SS mixtures indicated that these materials could be beneficial for biomass production, without contributing significant metal uptake or leaching. The application of FA as high as 560 Mg ha −1 in a long-term field trial had no detectable deterioration in soil or groundwater quality and no substantial increases in plant uptake of metals and other trace elements were observed. Low to moderate rates of FA and SS therefore could be successfully used as soil amendments, particularly so when used as a mixture.