Potential mineralization of nitrogen from organic wastes to ryegrass and wheat crops

Two-pot experiments with ryegrass and wheat plants were conducted in a Cambic Arenosol to test the reliability of N fate predicted by incubation experiments previously performed, with the same soil, to assess potentially mineralizable nitrogen from six organic wastes (municipal solid waste compost, secondary pulp mill sludge, horn meal, poultry manure, solid phase from pig slurry and composted pig manure). Two treatments, corresponding to 80 and 160 kgN/ha were tested, with or without mineral N fertilization. Experimental data obtained in the pot trials was consistent with nitrogen net mineralization trend observed in the aerobic incubations with all the wastes tested. Values of potentially mineralizable nitrogen (N(0)) from the equations obtained by model fitting, to the incubation data, were well correlated to ryegrass and wheat N uptake. Poultry manure was the most efficient N supplier to crops.     

Biological testing of a digested sewage sludge and derived composts

Aiming to evaluate a possible loss of soil habitat function after amendment with organic wastes, a digested sewage sludge and derived composts produced with green residues, where biologically tested in the laboratory using soil animals (Eisenia andrei and Folsomia candida) and plants (Brassica rapa and Avena sativa). Each waste was tested mimicking a field application of 6ton/ha or 12ton/ha. Avoidance tests did not reveal any impact of sludge and composts to soil biota. Germination and growth tests showed that application of composts were beneficial for both plants. Composts did not affect earthworm's mass increase or reproduction, but the highest sludge amendment revealed negative effects on both parameters. Only the amendment of composts at the highest dose originated an impairment of springtails reproductive output. We suggest that bioassays using different test species may be an additional tool to evaluate effects of amendment of organic wastes in soil. Biological tests are sensitive to pollutants at low concentrations and to interactions undetected by routine chemical analysis.     

Enumeration of Aeromonas hydrophila from domestic wastewater treatment plants and surface waters

Influents, effluents and sludges from sewage purification plants and surface water samples were examined quantitatively for Aeromonas hydrophila on the mA medium of Rippey and Cabelli. Between 10(4) and 10(6)/ml A. hydrophila were found in domestic wastewaters. On the average 99.975% were removed by activated sludge and 98.25% by trickling filters. Only 20.9% of A. hydrophila end up in the primary sludge, which contained up to 10(7)/g dry sludge. After 3 months, anaerobically (methane) fermented and partially dried sludge from trickling filters contained more than 10(6) A. hydrophila/g dry sludge. Surface water receiving raw sewage contained several hundreds of A. hydrophila/ml, comparable with the numbers found in effluent waters, while surface receiving no municipal wastewater and destined for the preparation of drinking water contained only small and negligible numbers. It was concluded that A. hydrophila was omnipresent in surface water.     

Heavy Metal Phytotoxicity to Radish (Raphanus sativus L.) in a Digested Sludge-amended Gangetic Alluvium

A limiting factor in land application of sewage sludge is the resultant heavy metal accumulation in soils followed by biomagnification in the food chain, posing a potential hazard to animal and human health. In view of this fact, pot experiments were conducted to evaluate the effect of digested sludge application to soil on phytotoxicity of heavy metals such as Cd, Cr, Ni, and Pb to radish (Raphanus sativus L.) plants. Increasing sludge levels resulted in increased levels of DTPA-extractable heavy metals in the soil. Cadmium was the dominant metal extracted by DTPA followed by Ni, Pb, and Cr. The extractability of metals by DTPA tended to decrease from the first to the second crop. Dry matter yield of radish increased significantly as a function of increasing sludge treatments. Soil application of sludge raised the concentration of one or more heavy metals in plants. Shoots contained higher concentrations of Cd, Cr, and Ni than the roots of radish plants. Shoot concentrations of Cd, Cr, Ni, and Pb were within the tolerance levels of this crop at all rates of sludge application. Shoot as well as root concentration of Cd was above 0.5 mg kg^?1, considered toxic for human and animal consumption. The levels of DTPA-extractable Cd and Ni were less correlated while those of Cr and Pb were more correlated with their respective shoot and root contents. The results emphasize that accumulation of potentially toxic heavy metals in soil and their build-up in vegetable crops should not be ignored when sludge is applied as an amendment to land.     

Improving grasslands: the influence of soil moisture and nitrogen fertilization on the establishment of seedlings

1. In order to investigate the factors influencing the establishment of seedlings in permanent grassland, the influence of soil moisture and nitrogen fertilization on competition between established plants of Lolium perenne and seedlings of Phleum pratense or Trifolium pratense was studied in two experiments under greenhouse conditions using the 'split-box'-technique.
2. There was no difference in the production of plant dry matter of P. pratense or T. pratense between 30% volumetric soil water content (−0·005 MPa) and 22% (−0·04 MPa), but 15% soil moisture (−0·33 MPa) reduced plant growth. L. perenne yields were linearly reduced by reduced soil moisture content.
3. Shoot competition from L. perenne reduced the plant dry matter yield of P. pratense and T. pratense more than did root competition in these experiments. When shoot competition was present, differences between moisture contents were not detected, indicating that light was probably the limiting resource under such conditions. No significant interaction between root competition and soil moisture was observed for plant weight.
4. Root competition was not prevented even though sufficient water and nitrogen were supplied. This indicated either that some other growth factor was limiting or the plants competed for resources at the root hair level even though sufficient resources were supplied at the pot or field scale. Therefore, in the situation of direct drilling of species during grassland renovation, it may be difficult to alleviate competition by adequate provision of water and nitrogen.     

Humic substances change during the co-composting process of municipal solid wastes and sewage sludge

The change of the degree of stability of compost during the composting process was a kind of guideline for our study. This stability was estimated by monitoring the chemical fractionation (extraction of humic and fulvic acids, and humin) during two cycles of composting. Change of humin (H), humic-like acid carbon (CHA) and fulvic-like acid carbon (CFA) fractions during the composting process of municipal solid wastes were investigated using two windrows W1 (100% of municipal solid wastes) and W2 (60% of municipal solid wastes and 40% of dried sewage sludge). Humin and fulvic acid fractions in the two windrows decreased since the start of composting process and tend to stabilize. At the end of composting process, humic acid fraction is more important in the windrow without sludge (W1) than the one with sludge (W2). The humification indexes used in this study showed that the humic-like acid carbon fraction production takes place largely during the phase of temperature increase (thermophilic phase), and it appeared very active in the windrow W2. At the end of composting process, the E₄/E₆ ratio value indicated that the compost of W1 is more mature than the compost of W2. The humification ratio (HR) allowed a correct estimation of compost organic matter stabilization level.     

Effects of pulp mill solids and three composts on early growth of tomatoes

Compost has been proposed as a means of simultaneously diverting organic materials from landfills while producing a valuable product that improves tilth, organic matter content and nutrient supply of agricultural soils. Composts manufactured from different source materials may have markedly different properties however, even if they meet all regulatory requirements. We compared the capacity of composts made from three different combinations of organic wastes (horse manure and bedding, mink farm wastes, municipal solid waste (MSW) and sewage sludge) along with clarifier solids from a chemo-thermomechanical pulp mill, to enhance the growth of tomato (Lycopersicon esculentum L.) seedlings grown in nutrient-poor organic potting soil. Germination and seedling emergence of tomatoes, cress (Lapidium sativum L.) or radish (Raphanus sativus L.) were tested to assess phytotoxicity of the four amendments. Mink farm compost and horse manure compost stimulated root and shoot growth of tomato seedlings but MSW compost and pulp mill solids were strongly inhibitory. MSW compost and unamended potting soil also inhibited seedling emergence and pulp mill solids produced stunting and deformities in radish and cress seedlings. Both toxic constituents and nutrient imbalances may be responsible for the growth-inhibiting effects of these amendments. Application of pulp mill solids to agricultural soil without composting may lead to deleterious effects on vegetable crops.     

城市污泥土地利用研究

通过培养试验、盆栽试验和田间试验系统地研究了污泥的组分特征、性质及其农地和城市园林绿化地利用对作物或绿化灌木、土壤肥力及其环境的影响,结果表明,污泥富含有机质和氮磷养分,且养分当季有效性介于化肥农家肥之间。施用污泥将明显提高土壤肥力,表现改善土壤物理性质;增加土壤肥机质和氮磷水平,并增加土壤生物活性,因此施用污泥的处理作物产量较高,并有利于后茬作物的稳健生长。但污泥施用也存在重金属、病原物等污染     

Effects of different sewage sludge applications on heavy metal accumulation,growth and yield of spinach (Spinacia oleracea L.)

In this study, we present the response of spinach to different amendment rates of sewage sludge (0, 10, 20, 30, 40 and 50 g kg^?1) in a greenhouse pot experiment, where plant growth, biomass and heavy metal uptake were measured. The results showed that sewage sludge application increased soil electric conductivity (EC), organic matter, chromium and zinc concentrations and decreased soil pH. All heavy metal concentrations of the sewage sludge were below the permissible limits for land application of sewage sludge recommended by the Council of the European Communities. Biomass and all growth parameters (except the shoot/root ratio) of spinach showed a positive response to sewage sludge applications up to 40 g kg^?1 compared to the control soil. Increasing the sewage sludge amendment rate caused an increase in all heavy metal concentrations (except lead) in spinach root and shoot. However, all heavy metal concentrations (except chromium and iron) were in the normal range and did not reach the phytotoxic levels. The spinach was characterized by a bioaccumulation factor <1.0 for all heavy metals. The translocation factor (TF) varied among the heavy metals as well as among the sewage sludge amendment rates. Spinach translocation mechanisms clearly restricted heavy metal transport to the edible parts (shoot) because the TFs for all heavy metals (except zinc) were <1.0. In conclusion, sewage sludge used in the present study can be considered for use as a fertilizer in spinach production systems in Saudi Arabia, and the results can serve as a management method for sewage sludge.     

Bacterial perspectives on the dissemination of antibiotic resistance genes in domestic wastewater bio-treatment systems: beneficiary to victim

Applied Microbiology and Biotechnology - Domestic wastes, ranging from sewage and sludge to municipal solid waste, are usually treated in bioprocessing systems. These systems are regarded as main...     

Analysis of the polyphosphate-accumulating microflora in phosphorus-eliminating, anaerobic-aerobic activated sludge systems by using diaminopropane as a biomarker for rapid estimation of Acinetobacter spp.

Polyphosphate-accumulating gram-negative bacteria were isolated from different anaerobic-aerobic activated sludge systems with diverse processes for enhanced biological phosphorus (P) elimination. Of 22 isolates, 10 were allocated to the genus Acinetobacter by using multiple-test systems and soluble protein and polyamine patterns. As diaminopropane (DAP) appears to be the characteristic main polyamine compound produced by Acinetobacter spp., it was used as a biomarker for the genus. The high DAP contents of representative samples from municipal wastes with enhanced biological P elimination indicated that Acinetobacter spp. can be dominant organisms in sewage treatment plants with low organic loading and nitrification and denitrification steps. Contrary to accepted opinion, sludge from treatment plants with efficient P removal and high organic loading had a low DAP content, indicating that bacteria other than Acinetobacter spp. are responsible for enhanced biological P elimination in these plants.     

Analysis of the polyphosphate-accumulating microflora in phosphorus-eliminating, anaerobic-aerobic activated sludge systems by using diaminopropane as a biomarker for rapid estimation of Acinetobacter spp.

Polyphosphate-accumulating gram-negative bacteria were isolated from different anaerobic-aerobic activated sludge systems with diverse processes for enhanced biological phosphorus (P) elimination. Of 22 isolates, 10 were allocated to the genus Acinetobacter by using multiple-test systems and soluble protein and polyamine patterns. As diaminopropane (DAP) appears to be the characteristic main polyamine compound produced by Acinetobacter spp., it was used as a biomarker for the genus. The high DAP contents of representative samples from municipal wastes with enhanced biological P elimination indicated that Acinetobacter spp. can be dominant organisms in sewage treatment plants with low organic loading and nitrification and denitrification steps. Contrary to accepted opinion, sludge from treatment plants with efficient P removal and high organic loading had a low DAP content, indicating that bacteria other than Acinetobacter spp. are responsible for enhanced biological P elimination in these plants.     

Improving the growth of Ni-hyperaccumulating plants in serpentine quarry tailings

Phytomining techniques based on metal-hyperaccumulating plants can be implemented in serpentine quarry wastes for Ni recovery. However, strategies must be developed to overcome the unfavourable plant growth conditions that these substrates present and to optimize Ni yields. In this study, the Ni hyperaccumulators Alyssum serpyllifolium, Alyssum inflatum, and Alyssum bracteatum were evaluated for their Ni phytoextraction efficiency from quarry tailings. Effects of two organic amendments, composted municipal sewage sludge and cow manure, on plant growth and physiological status and Ni removal were determined. Organic amendments were incorporated at two addition rates (5% and 20% w/w). The best-performing hyperaccumulators were A. inflatum and A. serpyllifolium. Organic amendments improved plant biomass production, photosynthetic efficiency and nutrition, but reduced shoot Ni concentrations. However, the stimulation in biomass resulted in significantly enhanced Ni yields. The most promising results were found using low addition rates and after manure incorporation.     

The effect of sewage sludge flooding on growth and morphometric parameters of Phragmites australis (Cav.) Trin. ex Steudel

Phragmites australis is the most frequently used species in constructed wetlands (CW) for dewatering and mineralization of sludge. Such CW create a very hostile environment for plants because their roots are exposed to permanently anaerobic conditions. Our working hypothesis assumed a simple relationship between the success of reed in colonising sludge flood stands and maximalisation of shoot oxygen production and transport to rhizomes and roots. Morphometric parameters and density of common reed shoots growing in reed bed systems inundated with sewage sludge were investigated. It was proved that flooding with sewage sludge significantly influenced characteristics of common reed populations. In comparison with natural stands, on stands treated with sewage sludge, maximal density of shoots was higher, biomass was twice as high, shoot diameter was significantly greater, and leaf weight ratio of an individual shoot was also significantly higher. Tendency to shorten shoots was noted. Growing period was longer for reed shoots treated with sewage sludge than on natural stands.     

Substitution of peat for municipal solid waste- and sewage sludge-based composts in nursery growing media: effects on growth and nutrition of the native shrub Pistacia lentiscus L

In this study, the effect of a partial substitution of peat for compost on the growth and nutrition of a native shrub (Pistacia lentiscus L.) was tested. Composts were prepared from pruning and municipal solid wastes or pruning waste and sewage sludge. For preparing growing media each compost was added at a rate of 40%, fresh pine bark at 20% or 40% and peat at 20%, 40% or 60%. Aqueous extracts from the substrates did not impair germination of cress (germination bioassay). In relation to plants growing in peat-based substrate (used as a control), plants of the compost-based substrates reached better growth and nutrition, especially when using the sewage sludge-based compost, and the P uptake was notably enhanced. The concentrations of trace elements were far lower than the ranges considered phytotoxic for vascular plants. Detrimental effect derived from using fresh pine bark was not observed.     

污泥堆肥对草坪草生长及光合特征的影响

研究不同污泥堆肥施用量(0、0.8%、2%、6%和10%)对高羊茅、黑麦草和早熟禾3种草坪草生长及光合特征的影响.结果表明: 污泥堆肥施用量为6%时效果最好.随污泥堆肥施用量的增加,高羊茅、黑麦草和早熟禾的株高、单叶面积和单株生物量均显著增加,根冠比显著降低,其中,株高增幅分别为64.9%～180.8%、97.3%～200.9%和39.1%～156.5%,单叶面积增幅分别为91.3%～417.4%、186.4%～394.9%和164.6%～508.3%,单株生物量增幅分别为333.4%～867.6%、138.4%～445.1%和316.3%～669.2%.随污泥堆肥施用量的增加,高羊茅净光合速率(P_n)、胞间CO₂浓度(C_i)、蒸腾速率(T_r)和水分利用效率(WUE)呈先增加后降低的趋势;早熟禾P_n、T_r和WUE逐渐增加,C_i呈先增加后降低的趋势;黑麦草P_n和WUE逐渐增加,但其C_i和T_r呈先增加后降低的趋势.污泥堆肥施用使3种草叶绿素a、b和(a+b)含量增加,施用量>6%后叶绿素a、b和(a+b)含量下降,但叶绿素a/b变化不明显.
     

The occurrence of intestinal parasites in swine slurry and their removal in activated sludge plants

Thirteen intensive pig farms and two activated sludge treatment plants for pig slurry in north-western Spain were studied from April 2005 to June 2006 in order to evaluate the presence of enteric pathogens (Cryptosporidium, Giardia and helminths) and the efficiency with which they were removed. These parasites were present on 53%, 7% and 38% of the farms studied, respectively, with concentrations of 10(4)-10(5) oocysts per litre (/L) for Cryptosporidium, 10(3)cysts/L for Giardia and 10(2)-10(3) eggs/L for helminths. The overall removal of parasites in the pig slurry treatment plants ranged from 86.7% to over 99.99%. The results revealed a constant reduction at each stage of the treatment system, with activated sludge processes being the most effective treatment in reducing pathogens in pig slurry, 78-81% for Cryptosporidium oocysts and over 99.9% for helminth eggs. A heat drying procedure for sludge removed 4.3 log units of Cryptosporidium oocysts, demonstrating the excellent effectiveness of this treatment for reducing pathogens in sludge intended to be applied to land.     

Enumeration of Aeromonas hydrophila from domestic wastewater treatment plants and surface waters

R. POFFÉ AND E. OP DE BEECK. 1991. Influents, effluents and sludges from sewage purification plants and surface water samples were examined quantitatively for Aeromonas hydrophila on the mA medium of Rippey and Cabelli. Between 10⁴ and 10⁶/ml A. hydrophila were found in domestic wastewaters. On the average 99.975% were removed by activated sludge and 98.25% by trickling filters. Only 20.9% of A. hydrophila end up in the primary sludge, which contained up to 10⁷/g dry sludge. After 3 months, anaerobically (methane) fermented and partially dried sludge from trickling filters contained more than 10⁶ A. hydrophila /g dry sludge. Surface water receiving raw sewage contained several hundreds of A. hydrophila /ml, comparable with the numbers found in effluent waters, while surface water receiving no municipal wastewater and destined for the preparation of drinking water contained only small and negligible numbers. It was concluded that A. hydrophila was omnipresent in surface water.     

Free-living pathogenic and nonpathogenic amoebae in Maryland soils

Tests for potentially pathogenic amoebae were carried out on soil samples from the following sites: (i) farmlands fertilized with municipal sewage wastes, (ii) a stream receiving sewage effluent from a sludge lagoon, (iii) a ravine receiving storm runoff from a cattle farm, (iv) farmlands not fertilized with sewage wastes, and (v) a vegetated shoreline of a waterfront estate not used for farming or livestock production. Study sites were located on the eastern shore of Maryland, bordered to the north by Delaware and to the south by Virginia. Twenty-four species of soil amoebae, including five potentially pathogenic Acanthamoeba species (members of the family Acanthamoebidae), were identified. All of the sites yielded two or more of the potential pathogens.     

Free-living pathogenic and nonpathogenic amoebae in Maryland soils.

Tests for potentially pathogenic amoebae were carried out on soil samples from the following sites: (i) farmlands fertilized with municipal sewage wastes, (ii) a stream receiving sewage effluent from a sludge lagoon, (iii) a ravine receiving storm runoff from a cattle farm, (iv) farmlands not fertilized with sewage wastes, and (v) a vegetated shoreline of a waterfront estate not used for farming or livestock production. Study sites were located on the eastern shore of Maryland, bordered to the north by Delaware and to the south by Virginia. Twenty-four species of soil amoebae, including five potentially pathogenic Acanthamoeba species (members of the family Acanthamoebidae), were identified. All of the sites yielded two or more of the potential pathogens.