Agricultural Use Of Sewage Sludge Research Articles

Combustion of Sewage Sludge: Kinetics and Speciation of the Combustible

Combustion of sewage sludge has become a viable route for sewage sludge management especially as the agricultural use of sewage sludge has become increasingly difficult due to more stringent requirements regarding the quality of sewage sludge. Combustion of digested sewage sludge in dedicated monocombustion facilities is advantageous, as it substantially reduces the volume of the sludge and still allows for a recovery of phosphorus from the sewage sludge ash at a later stage. Despite increasing amounts of sewage sludge being combusted, knowledge on the respective combustion kinetics is still fragmentary. The goal of this study was, therefore, to identify the major combustion reactions of sewage sludge, assess their Arrhenius parameters (activation energy and pre-exponential factor), and assign suitable reference compounds to the individual reactions. For that purpose, experiments were conducted using a thermogravimetric analyzer (TGA). With matrix inversion, we identified 10 individual reactions. Despite ...

Utilização do lodo de esgoto na agricultura: uma análise cienciométrica

O lodo de esgoto é rico em matéria orgânica e nutrientes que podem favorecer as propriedades físico-químicas dos solos e o desenvolvimento de culturas. Entretanto, a concentração de microrganismos patogênicos, elementos-traço e poluentes orgânicos persistentes são fatores limitantes para a aplicação deste material no solo. Este trabalho objetivou verificar a evolução da publicação de artigos sobre o uso agrícola do lodo de esgoto, entre os anos de 1980 a 2017. Para isso, foi realizada uma pesquisa de artigos científicos indexados no banco de dados Web of Science relacionados ao tema, sendo encontrados 1.166 artigos. Os resultados obtidos mostram que houve um aumento gradativo do número de publicações entre as décadas. Dentre os países que mais publicaram sobre o tema destacam-se os Estados Unidos, Espanha e Brasil. Verificou-se nos artigos que tratavam da presença de poluentes que 35,5% apresentaram informações sobre os elementos-traço; 13,7% acerca dos patógenos; 15% sobre os poluentes orgânicos; enquanto 27% abordavam os nutrientes, com destaque para o fósforo, nitrogênio e potássio. Com relação às culturas, as mais mencionadas foram os cereais, destacando-se o milho. A partir dos dados analisados foi possível observar o aumento no percentual de publicações ao longo dos anos sobre o tema, o que sugere uma preocupação cada vez maior com a destinação do lodo, contudo, a presença de poluentes ainda representa um desafio para seu uso agrícola, devendo, por isso, ser submetido a tratamentos para reduzir sua carga poluidora e ser utilizado cautelosamente de acordo com o estabelecido pela legislação.

Effects of Medium-Term Amendment with Diversely Processed Sewage Sludge on Soil Humification-Mineralization Processes and on Cu, Pb, Ni, and Zn Bioavailability.

The organic fraction of sewage sludge administered to agricultural soil can contribute to slowing down the loss of soil’s organic carbon and, in some cases, can improve the physical and mechanical properties of the soil. One of the main constraints to the agricultural use of sewage sludge is its heavy metals content. In the long term, agricultural administration of sewage sludge to soil could enhance the concentration of soil heavy metals (as total and bioavailable fractions). The aim of this research was to evaluate the effects of medium-term fertilization with diversely processed sewage sludge on the soil’s organic carbon content and humification–mineralization processes, on the physical–mechanical properties of soil and their influence on the pool of potentially bioavailable heavy metals, in order to assess their effectiveness as soil organic amendments. After eight years of sludge administration; an increase in the concentrations of bioavailable form was evidenced in all the heavy metals analyzed; independently of the type of sludge administered. The form of sludge administration (liquid, dehydrated, composted) has differently influenced the soil humification–mineralization processes and the physical–mechanical properties of soil. The prolonged amendment with composted sewage sludge contributed to keeping the soil humification–mineralization process in equilibrium and to improving the physical and mechanical qualities of the treated soil.

Lodo de esgoto: diretrizes e o seu uso como fertilizante, condicionador de solo e substrato florestal

O lodo de esgoto é um resíduo gerado após o tratamento dos esgotos e consiste em um problema ambiental crescente, devido ao aumento das redes de coleta e tratamento desses efluentes. A disposição desse resíduo na agricultura vem se apresentando como a mais adequada, com efeitos positivos apontados por várias pesquisas. No entanto, existem critérios e procedimentos que devem ser contemplados para o gerenciamento legal do lodo. Serão apresentadas as principais diretrizes para utilização do lodo na agricultura, sua influência na fertilidade do solo, como condicionador de solo, e seu desempenho como substrato florestal, destacando os pontos positivos e negativos.

Agricultural use of sewage sludge in India: benefits and potential risk of heavy metals contamination and possible remediation options - a review

Application of municipal sewage sludge in agriculture is one of the best options for its safe disposal as it provides an opportunity to recycle plant essential nutrients (N, P, secondary nutrients and micronutrients) and improves soil physical, chemical and biological properties due to high organic matter content. Yield and productivity of a wide range of crops has been improved due to soil application of sewage sludge than that of well-fertilised control. Depending upon the origin, sewage sludge often contains very high amount of potentially toxic heavy metals and as such their excessive use for a longer period increases metal bioavailability in soil and ultimately causes food chain contamination. In this article we reviewed the available information on various aspects of land application of municipal sewage sludges on crop yield, soil fertility and problems of heavy metals accumulation in edible portion of the crops as well as possible options for remediation of heavy metals toxicity in contaminated soils to explore the possibility of safe recycling this waste in agriculture.

EFFECT OF SEWAGE SLUDGE APPLICATION ON WHEAT CROP PRODUCTIVITY AND HEAVY METAL ACCUMULATION IN SOIL AND WHEAT GRAIN

The present work illustrates the results of a long-term field experiment with sewage sludge used on agricultural land in order to assess the influence of sewage sludge on wheat crop productivity. The experimental research was conducted for three years as following: the evaluation of the agricultural use of sewage sludge in the year of application and its residual effect in grain and in soil for the next two years. The sewage sludge considered in the framework of the study was from Sfantu Gheorghe wastewater treatment plant, Covasna County (non-fermented sewage sludge from the dewatering press), Romania. Through the laboratory work, the heavy metals content in sewage sludge, soil, sewage sludge and soil (mixed sample) and wheat was identified. The attention was mainly focused on heavy metals content of sewage sludge because these kinds of contaminants are currently the most significant factor limiting its reuse in agriculture. In this way, the potential impacts of emerging micro-pollutants as cadmium (Cd) and lead (Pb) existing in sludge have been investigated. The results from our field experiments showed positive results related to sewage sludge spreading on agricultural land. Using chemical fertilizer and different doses of sewage sludge (0, 10, 25 and 40 t/ha), it was observed an improvement in the amount of harvested grain. It was demonstrated that a dose of 25 t/ha sewage sludge application provides highest wheat crop productivity, while Cd and Pb concentration levels in soil and wheat grain were under the maximum values allowed by the regulation.

Agricultural use of sewage sludge in India: benefits and potential risk of heavy metals contamination and possible remediation options - a review

Application of municipal sewage sludge in agriculture is one of the best options for its safe disposal as it provides an opportunity to recycle plant essential nutrients (N, P, secondary nutrients and micronutrients) and improves soil physical, chemical and biological properties due to high organic matter content. Yield and productivity of a wide range of crops has been improved due to soil application of sewage sludge than that of well-fertilised control. Depending upon the origin, sewage sludge often contains very high amount of potentially toxic heavy metals and as such their excessive use for a longer period increases metal bioavailability in soil and ultimately causes food chain contamination. In this article we reviewed the available information on various aspects of land application of municipal sewage sludges on crop yield, soil fertility and problems of heavy metals accumulation in edible portion of the crops as well as possible options for remediation of heavy metals toxicity in contaminated soils to explore the possibility of safe recycling this waste in agriculture.

Soil fertility, growth and mineral nutrition in Eucalyptus grandis plantation fertilized with different kinds of sewage sludge

The agricultural use of sewage sludge has increased worldwide, especially in crops and in countries with temperate or subtropical climate. Nevertheless, few studies have been conducted with forest plantations in tropical conditions. This study aimed to evaluate the soil fertility, mineral nutrition and tree growth in Eucalyptus grandis plantations fertilized with three types of sewage sludge. The design used was of blocks with randomized plots, four replications and five treatments: control without fertilization (C), conventional mineral fertilizer (MF), fertilization with 15 t ha−1 (dry basis) of sewage sludge produced in wastewater treatment plants of Barueri (BS), Sao Miguel (SS) and Parque Novo Mundo (PS) cities, all located in the metropolitan region of Sao Paulo, Brazil. It was observed that the application of sewage sludge increased the content of organic matter, nitrogen and phosphorus in the layer of 0–5 cm soil depth, as well as the nitrogen, phosphorus, copper and zinc concentrations in the Eucalyptus leaves. In the PS treatment, the sludge (conditioned with quicklime) application also increased the pH and the concentration of calcium in the soil compared to other kinds of sludge (conditioned with polyelectrolyte), resulting in higher Ca:Mg and Ca:K ratios in the leaves. Probably for this reason, wood production in PS was 20 % lower than in the MF treatment at 60 months of age of the trees. Even so, the fertilization with sewage sludge provided a rise of 50–90 % in timber volume compared to C treatment.

Phosphorus recovery from municipal wastewater: An integrated comparative technological, environmental and economic assessment of P recovery technologies

Phosphorus (P) is an essential and limited resource. Municipal wastewater is a promising source of P via reuse and could be used to replace P derived from phosphate rocks. The agricultural use of sewage sludge is restricted by legislation or is not practiced in several European countries due to environmental risks posed by organic micropollutants and pathogens. Several technologies have been developed in recent years to recover wastewater P. However, these technologies target different P-containing flows in wastewater treatment plants (effluent, digester supernatant, sewage sludge, and sewage sludge ash), use diverse engineering approaches and differ greatly with respect to P recycling rate, potential of removing or destroying pollutants, product quality, environmental impact and cost. This work compares 19 relevant P recovery technologies by considering their relationships with existing wastewater and sludge treatment systems. A combination of different methods, such as material flow analysis, damage units, reference soil method, annuity method, integrated cost calculation and a literature study on solubility, fertilizing effects and handling of recovered materials, is used to evaluate the different technologies with respect to technical, ecological and economic aspects. With regard to the manifold origins of data an uncertainty concept considering validity of data sources is applied. This analysis revealed that recovery from flows with dissolved P produces clean and plant-available materials. These techniques may even be beneficial from economic and technical perspectives under specific circumstances. However, the recovery rates (a maximum of 25%) relative to the wastewater treatment plant influent are relatively low. The approaches that recover P from sewage sludge apply complex technologies and generally achieve effective removal of heavy metals at moderate recovery rates (~40–50% relative to the WWTP input) and comparatively high costs. Sewage sludge ash is the most promising P source, with recovery rates of 60–90% relative to the wastewater P. The costs highly depend on the purity requirements of the recycled products but can be kept comparatively low, especially if synergies with existing industrial processes are exploited.

Assessing the probability of infection by Salmonella due to sewage sludge use in agriculture under several exposure scenarios for crops and soil ingestion

A deeper understanding about the risks involved in sewage sludge practice in agriculture is required. The aims of the present study were to determine the annual risk of infection of consuming lettuce, carrots and tomatoes cultivated in soil amended with sewage sludge. The risk to agricultural workers of accidental ingestion of sludge or amended soil was also investigated.A Quantitative Microbial Risk Assessment was conducted based on Salmonella concentrations from five WWTPs were used to estimate the probability of annual infection associated with crops and soil ingestion. The risk of infection was estimated for nine exposure scenarios considering concentration of the pathogen, sewage sludge dilution in soil, variation of Salmonella concentration in soil, soil attachment to crops, seasonal average temperatures, hours of post-harvesting exposure, Salmonella regrowth in lettuce and tomatoes, Salmonella inhibition factor in carrots, crop ingestion and frequency of exposure, sludge/soil ingestion by agricultural workers and frequency of exposure. Annual risks values varied across the scenarios evaluated. Highest values of annual risk were found for scenarios in which the variation in the concentration of Salmonella spp. in both soil and crops (scenario 1) and without variation in the concentration of Salmonella spp. in soil and variation in crops (scenario 3) ranging from 10−3 to 10−2 for all groups considered. For agricultural workers, the highest annual risks of infection were found when workers applied sewage sludge to agricultural soils (2.26×10−2). Sensitivity analysis suggests that the main drivers for the estimated risks are Salmonella concentration and ingestion rate. These risk values resulted from conservative scenarios since some assumptions were derived from local or general studies. Although these scenarios can be considered conservative, the sensitivity analysis yielded the drivers of the risks, which can be useful for managing risks from the fresh products chain with stakeholders' involvement.

KENTSEL KATI ATIK KOMPOSTU VE ARITMA ÇAMURUNDA AĞIR METALLERİN BİTKİLER VE ÇEVRE ÜZERİNDE POTANSİYEL ETKİLERİ VE KİRLETİCİ LİMİTLER

Kentsel kati atik kompostu ve aritma camuru uygulanan topraklarda bitkisel uretim, cevre ve tuketiciler ve surdurulebilir toprak idaresi uzerinde risk tasiyan, istenmeyen agir metal birikimi gorulebilmektedir. Aritma camurunun tarimda kullanilmasina iliskin, risk-esasli yaklasima gore guncellestirilmis sinir degerler ve uygulama kriterleri getirilmistir. Tarimda camur kullaniminda sunulan bu yasal duzenlemelerdeki kriterlere uyuldugunda bitkisel uretim, cevre ve tuketiciler icin yonetilebilir bir risk tasidigi belirtilmektedir. Halihazirda, kentsel kati atik kompostu kalite kriterlerine ozgu uluslararasi kabul edilen bir standart ya da yonetmelik bulunmamaktadir. Kompost kalitesinin duzenlenmesinde esas alinan yaklasimlara bagli olarak kentsel kati atik kompostunda agir metal kirleticilerine iliskin standartlar ulkeler arasinda genis bir yelpazede farklilik gostermektedir. Bir cok bakimdan, kentsel kati atik kompostunun aritma camuruna benzerligi nedeniyle, aritma camuru hakkinda elde olunan bilgilerin cogu, kentsel kati atik kompostlarina uygulanabilmektedir.

Concentration of Cu, Zn, Cr, Ni, Cd, and Pb in soil, sugarcane leaf and juice: residual effect of sewage sludge and organic compost application.

Many researchers have evaluated the effects of successive applications of sewage sludge (SS) on soil plant-systems, but most have not taken into account the residual effect of organic matter remaining from prior applications. Furthermore, few studies have been carried out to compare the effects of the agricultural use of SS and sewage sludge compost (SSC). Therefore, we evaluated the residual effect of SS and SSC on the heavy metal concentrations in soil and in sugarcane (Saccharum spp.) leaves and juice. The field experiment was established after the second harvesting of unburned sugarcane, when the organic materials were applied. The SS and SSC rates were (tha(-1), dry base): 0, 12.5, 25, and 50; and 0, 21, 42, and 84, respectively. All element concentrations in the soil were below the standards established by São Paulo State environmental legislation. SS promoted small increases in Zn concentrations in soil and Cu concentrations in leaves. However, all heavy metals concentrations in the leaves were lower than the limits established for toxic elements and were in accordance with the limits established for micronutrients. There were reductions in the concentrations of Ni and Cu in soil and the concentration of Pb in juice, with increasing rates of SSC. The heavy metal concentrations were very low in the juice. Under humid tropical conditions and with short-term use, SS and SSC containing low heavy metal concentrations did not have negative effects on plants and soil.

Reakcja kukurydzy uprawianej na ziarno po zastosowaniu osad�w sciekowych

The aim of this study was to assess the effects of the agricultural use of sewage sludge in corn for grain, in the year of application and follow up effect after one and two years after its application. The study was conducted on the variety PR39G12 on the field after the 5-year monoculture corn. Sewage sludge was used in accordance with the Directive of Minister of Environment allowing application of 10 t dry mater per ha-1 once every five years. Fertilization with sludge of maize grown for grain did not cause differences in the growth and development of plants, compared to mineral fertilized objects, as well as did not exceed the limit value for heavy metals content in above-ground plant parts. Maize grown using sewage sludge yielded higher than the objects fertilized with mineral, especially in conditions of extreme drought, which occurred in 2006. Beneficial effect of sewage sludge was maintained in the next two years after application and stabilized the grain yield of maize.

Agricultural potential of an industrial sewage sludge in compliance with CONAMA Resolution no. 375/2006

The agricultural use of sewage sludge is one of the best alternatives to disposal because of its potential as a plant fertilizer and soil conditioner. However, to be safe for agricultural use, the sewage sludge must be evaluated according to its physical, chemical, and biological properties and its origin. In Brazil, NBR 10.004/2004 is the standard that determines the classification of solid waste, and CONAMA Resolution 375/2006 defines the criteria for the agricultural use of sewage sludge. This study evaluated the agricultural potential of an aerobically digested industrial sewage sludge from the Serramar Dairy Cooperative in the city of Guaratinguetá, São Paulo. This sludge was classified as Class IIA waste according to NBR 10.004/2004 and displayed potential for agricultural use by falling within the limits in terms for heavy metals and pathogenic organisms established by Resolution 375/2006 as well as containing high levels of nutrients. To establish the sludge doses allowed for application to crops such as maize (annual) and Eucalyptus sp. (perennial) by the resolution, the amount of nitrogen available in the sludge and the amounts of this nutrient required by these crops were considered. The recommended sewage sludge doses for corn (8 Mg ha- 1) and Eucalyptus sp. forestation (6 Mg ha- 1) can meet the nitrogen and phosphorus needs of these crops but require supplementation with potassium mineral fertilizer.

Agricultural potential of an industrial sewage sludge in compliance with CONAMA Resolution no. 375/2006

The agricultural use of sewage sludge is one of the best alternatives to disposal because of its potential as a plant fertilizer and soil conditioner. However, to be safe for agricultural use, the sewage sludge must be evaluated according to its physical, chemical, and biological properties and its origin. In Brazil, NBR 10.004/2004 is the standard that determines the classification of solid waste, and CONAMA Resolution 375/2006 defines the criteria for the agricultural use of sewage sludge. This study evaluated the agricultural potential of an aerobically digested industrial sewage sludge from the Serramar Dairy Cooperative in the city of Guaratinguetá, São Paulo. This sludge was classified as Class IIA waste according to NBR 10.004/2004 and displayed potential for agricultural use by falling within the limits in terms for heavy metals and pathogenic organisms established by Resolution 375/2006 as well as containing high levels of nutrients. To establish the sludge doses allowed for application to crops such as maize (annual) and Eucalyptus sp. (perennial) by the resolution, the amount of nitrogen available in the sludge and the amounts of this nutrient required by these crops were considered. The recommended sewage sludge doses for corn (8 Mg ha- 1) and Eucalyptus sp. forestation (6 Mg ha- 1) can meet the nitrogen and phosphorus needs of these crops but require supplementation with potassium mineral fertilizer.

DECOMPOSIÇÃO DE LODO DE ESGOTO E COMPOSTO DE LODO DE ESGOTO EM NITOSSOLO HÁPLICO

RESUMO O uso agrícola de lodo de esgoto e derivados no Estado de São Paulo é regulamentado por norma federal e por norma paulista, que recomendam que esses materiais quando incorporados a solos agrícolas devem apresentar no mínimo 30 % de degradação do carbono total. Para observar as frações de degradação de um lodo de esgoto e de um composto, produzido a partir do mesmo lodo juntamente com poda de árvore urbana triturada, realizaram-se dois ensaios de biodegradação de C. As doses dos resíduos foram adicionadas em frascos contendo 500 g de solo coletado na profundidade de 0,00-0,20 m de um Nitossolo Háplico Álico textura argilosa. No ensaio I, as doses de lodo (L) e composto (C) utilizadas consideraram percentuais da necessidade em N para a cultura da cana-de-açúcar, e expressas em Mg ha-1 de resíduo (base úmida): L1 21,2 (100 %); L2 42,4 (200 %); C1 69,4 (50 %); C2 138,9 (100 %); e C3 277,8 (200 %). O ensaio II foi realizado apenas com o lodo de esgoto, utilizando-se doses 5, 10, 15 e 20 vezes maiores que aquelas recomendadas no ensaio I: L3 120; L4 240; L5 360; e L6 480, simulando sucessivas aplicações do resíduo no solo. O C-CO2liberado foi quantificado por meio da medida de condutividade elétrica. O lodo de esgoto no ensaio I apresentou menores frações de degradação quando comparado ao composto orgânico, mas a taxa de decomposição do composto foi menor, provavelmente pela presença de substâncias recalcitrantes resultantes do processo de humificação. A fração de degradação dos resíduos no solo atingiu valor próximo a 30 % apenas para a dose de lodo de esgoto 20 vezes superior à dose exigida pela cultura, e assim não poderiam ser utilizados em solos agrícolas argilosos. Observou-se a necessidade de revisão desse valor adotado pela legislação paulista de uso de resíduos orgânicos em solos.

Characterization of Dissolved Organic Matter from Sewage Sludge using 3D-Fluorescence Spectroscopy and Chemometric Tools

The aim of the present article is to show the possibilities of chemometric tools and the parallel factor analysis (PARAFAC) model, as well as to understand the complexities of the fluorescence emission-excitation matrix (EEM) of water-soluble organic matter (WSOM) extracted from sewage sludge samples obtained with different origins and stabilization procedures. The variation in the composition of WSOM in the different sewage sludge samples could be correlated with the conditions of stabilization; therefore, the use of fluorescence spectroscopy to monitor these changes can be a useful tool to optimize the management of this residual flux, avoiding environmental pollution. However, the “contour density” EEM maps obtained with fluorescence present continuous spectra with different peaks, valleys, and shoulders where manual peak picking can be complicated and subjective, especially in complex matrixes such as sewage sludge. With the PARAFAC algorithm, it is possible to resolve the emission and excitation spectra of the different fluorescence components present in the samples and their contribution to the total fluorescence. Also, the contribution (scores) of the different fluorophors can be coupled with another chemometric tool to provide an effective classification method using the stabilization conditions of sewage sludge as main criterion. In this study, a wide survey of sewage sludge samples (287) was characterized by fluorescence emission-excitation matrix. The final molecular composition of the sewage sludge samples was not related to the stabilization (aerobic vs anaerobic) treatments. However, a sewage sludge classification based on a combined spectroscopic-chemometric approach was obtained, which could be used for the optimization of sewage sludge use in agriculture, minimizing the environmental risks.

REDUÇÃO DA VIABILIDADE DE OVOS DE HELMINTOS EM LODO DE ESGOTO DOMÉSTICO CALEADO - DOI: 10.13083/1414-3984.v22n01a05

O aproveitamento agrícola do lodo de esgoto apresenta-se como uma alternativa viável para sua disposição final. Entretanto, para sua reutilização e destinação correta, é necessária sua estabilização. Os objetivos com a condução deste trabalho foram: quantificar a concentração de ovos de helmintos viáveis no lodo; avaliar a sobrevivência desses ovos no lodo submetido a diferentes tempos de caleação e classificar o lodo, segundo a Resolução CONAMA nº 375, no que se refere a uso agrícola. O experimento foi constituído por três tratamentos e quatro repetições. Os tratamentos foram: caleação do lodo de esgoto com dose de cal necessária a manutenção do pH acima de 12, por 72 h; caleação do lodo de esgoto com dose de cal necessária a manutenção do pH acima de 12, por 2 h, e lodo de esgoto sem adição de cal. Para comparar a concentração de ovos de helmintos entre os tratamentos foram ajustados modelos lineares generalizados, utilizando distribuição de erro Poisson corrigida para Quase-Poisson, e submetidos ao teste F. A caleação do lodo por 2 e 72 h promoveu a inativação de 93,75 e 99,32% dos ovos de helmintos, sendo o lodo, após o tratamento, classificado como Classe B e Classe A, respectivamente. Do ponto de vista sanitário, o tempo de 72 h forneceu um lodo mais seguro para uso agrícola.

Pasture and soil zinc evolution in forest and agriculture soils of Northwest Spain three years after fertilisation with sewage sludge

The main problem with the agricultural use of sewage sludge is the higher heavy metal (mainly zinc) concentrations in the sludge than in the soil. In Spain, R.D. 1310/1990 and European Directive 86/278 limit the total heavy metal concentration in soil but not the changes in heavy metal availability, which directly affect plant absorption and thereby represent a possible risk to human health. The heavy metal availability in soil depends on different factors (pH, soil organic matter, and weather) and the type of soil (agriculture or forest). This study evaluate the effects of two types of soils (forest and agriculture), two types of vegetation (natural and sown), and two types of fertilisation (sludge fertilisation and mineral fertilisation, with a no fertiliser control) in afforested and treeless pastures and in sown and unsown forestlands of Northwest Spain on the total and available Zn concentration in soil and the concentration of Zn in grasslands. The experimental design was completely randomised with nine treatments and three replicates. The fertilisation with sewage sludge increased the total, Mehlich 3 and sward Zn concentrations in forest and agriculture soils, and the levels of Zn were lower in the forest than in the agriculture soils probably because of the low soil pH in the former which probably limited the mineralisation of the sludge in the forest soil. Therefore, there is still a potential source of Zn in forest soils than in agriculture soils, when the incorporation conditions improve. This makes advisable to extend the period without grazing after sewage sludge inputs in forest than agriculture soils to avoid direct Zn intake by animals through the soil consumption. The effect of the application of sewage sludge on sward Zn concentrations was more relevant in unsown pastures of forest soils than in agriculture soils due to the different absorption capacity of unsown compared with sown species. Zinc inputs from sewage sludge to soils did not cause harmful effects on plants or animals. However, the management of heavy metal availability must be included by policy makers in further directives to better evaluate environmental risk. Moreover, Zn maintenance requirements of animals like goats, horses, bovines and ovine were not often reached, which may make advisable to provide Zn supplement to animals if their nourishment is derived solely from these pastures.

Study of sewage sludge use in agriculture and its effect on plant and soil

The plant macro and micro nutrients as well as organic matter make sludge disposal in soil an attractive option. Nitrogen has received most attention and it is normally the most abundant sludge nutrient. One of the best alternatives to waste disposal is through the soil-plant system as a fertilizer. Based on properties different wastes can be co-recycled in order to take simultaneously the best profit and minimize environmental pollution .An experiment was carried out with a calcareous soil. Using six different doses of a sewage sludge were treated. A crop barley (Hordium Vulgare, Giza 123 ) was grown in the amended soils. The application of sewage sludge to the calcareous soil lowered the pH of the soil, although the value always around 7.757.9 at the end of the experiment. In the barley plants it was observed that the higher the yield, the higher the nitrogen contents. Electrical conductivity rose with organic amendment. Also it improved the nutrient level of the soil, particularly nitrogen and available phosphorus.