Spatial distribution of dynamics characteristic in the intermittent aeration static composting of sewage sludge

Spatial differences and temporal changes in biological activity characteristics were investigated in a static reactor using intermittent aeration during the sewage sludge composting process. Pumice was proposed as a bulking agent in the composting of sewage sludge. Variations in temperature, moisture, oxygen level, volatile solids, specific oxygen uptake rate (SOUR) and dehydrogenase activity (DHA) were determined during 28 days of composting. The peak temperature in the upper region of the reactor was 10 °C higher than that at the bottom. The moisture level in the middle region was significantly higher than that of other positions. Analysis of SOUR and DHA indicated that the lowest level of sludge stability was at the bottom region. These spatial and temporal differences in biochemical dynamics in the static system could extend the composting period and affect product uniformity.     

Evolution of clostridia and streptomycetes in full-scale composting facilities and pilot drums equipped with on-line temperature monitoring and aeration

The evolution of sporulating bacteria in full-scale composting facilities with online temperature monitoring has been poorly studied, although organic matter recycling increases. We analysed Clostridium perfringens and sulphite-reducing clostridia (SRC) by cultivation, and streptomycetes by real-time PCR in five full-scale, temperature-monitored and aerated composting processes, and two pilot-scale drum composters. Facilities composted woodchips, sawdust, peat, or bark amended sludge or source-separated biowaste. Streptomycetes genes of 0.21-110 × 10⁷ copies/g feed increased fast to 0.019-33 × 10⁹ copies/g, and then were equal or decreased. SRC of 0.06-2.2 × 10⁷ cfu/g feed decreased to 0-600 cfu/g, with re-growth in two facilities. End products were clean of C. perfringens, detected in sludge composts. Although processes contained large quantities of spore-forming bacteria, in the best facilities end products had the high quality. Temperature (>55 °C, >2d) was not related to the end compost quality, but relations between waste and bulking agent qualities, aeration, and processing time should be better controlled.     

Response of compost maturity and microbial community composition to pentachlorophenol (PCP)-contaminated soil during composting

Two composting piles were prepared by adding to a mixture of rice straw, vegetables and bran: (i) raw soil free from pentachlorophenol (PCP) contamination (pile A) and (ii) PCP-contaminated soil (pile B). It was shown by the results that compost maturity characterized by water soluble carbon (WSC), TOC/TN ratio, germination index (GI) and dehydrogenase activity (DA) was significantly affected by PCP exposure, which resulted in an inferior degree of maturity for pile B. DGGE analysis revealed an inhibited effect of PCP on compost microbial abundance. The bacteria community shifts were mainly consistent with composting factors such as temperature, pH, moisture content and substrates. By contrast, the fungal communities were more sensitive to PCP contamination due to the significant correlation between fungal community shifts and PCP removal. Therefore, the different microbial community compositions for properly evaluating the degree of maturity and PCP contamination were suggested.     

Bioremediation of PAHs-contaminated soil through composting: Influence of bioaugmentation and biostimulation on contaminant biodegradation

The degradation of several polycyclic aromatic hydrocarbons (PAHs) in soil through composting was investigated. The selected PAHs included: fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, and chrysene, with concentrations simulating a real creosote sample. The degradation of PAHs (initial concentration 1 g of total PAHs kg⁻¹ dry soil) was assessed applying bioaugmentation with the white-rot fungi Trametes versicolor and biostimulation using compost of the source-selected organic fraction of municipal solid waste (OFMSW) and rabbit food as organic co-substrates. The process performance during 30 days of incubation was evaluated through different analyses including: dynamic respiration index (DRI), cumulative oxygen consumption during 5 days (AT₅), enzymatic activity, and fungal biomass. These analyses demonstrated that the introduced T. versicolor did not significantly enhance the degradation of PAHs. However, biostimulation was able to improve the PAHs degradation: 89% of the total PAHs were degraded by the end of the composting period (30 days) compared to the only 29.5% that was achieved by the soil indigenous microorganisms without any co-substrate (control, not amended). Indeed, the results showed that stable compost from the OFMSW has a greater potential to enhance the degradation of PAHs compared to non-stable co-substrates such as rabbit food.     

Mites associated with stored products in Greece

A faunistic survey of mites was conducted in many product stores during a 6-year study period, 2000–2005, in Greece. A total of 1,073 samples were taken from 34 Greek counties. The survey was carried out on grains (wheat, maize, oat, barley), flour, bran, manufactured agricultural foodstuffs, dried fruits (figs, raisins), residues and dust, stored in varying quantities in five types of storage facilities (stores of agricultural cooperative unions, farm stores, commercial stores, flour mills and silos). Dominance-frequency analysis and redundancy analysis (RDA) were used to reveal the preferences of the collected taxa. Approximately 55% of the samples contained mites and 65 mite taxa were identified, belonging to 15 families in four orders. Six species, namely, Acarus gracilis Hughes, A. immobilis Griffiths, Caloglyphus oudemansi (Zachvatkin), Suidasia medanensis Oudemans, Tyrophagus perniciosus Zachvatkin and Kleemania plumigera (Oudemans), were new to the fauna of Greece. Five species, Tyrophagus similis Volgin, Blattisocius mali (Oudemans), Neoseiulus barkeri (Hughes), Cheyletus cacahuamilpensis Baker and Storchia robustus (Berlese), were recorded for the first time in stored products in Greece. Lepidoglyphus destructor (Schrank), Tyrophagus putrescentiae (Schrank) and Acarus siro L. were dominant or intermediate in all storage facilities examined. Cheyletus malaccensis Oudemans was the most common predatory mite. The highest percentage of infestation (65.3) was recorded in the samples from stores of agricultural cooperative unions. Residue-type materials had the highest degrees and percentages of infestation.     

Comparison Between Radiological and Chemical Health Risks Assessments: The Nord-Cotentin Study

In 1997, the French Ministries of the Environment and Health commissioned a detailed radioecological analysis of the Nord-Cotentin region in response to public concern about radiological risks associated with local nuclear facilities. This work was entrusted to the Groupe Radioécologie Nord-Cotentin (GRNC), a working group of experts from various origins (industrial facilities operators, public institutions, monitoring agencies, public interest and citizens groups, foreign experts). An epidemiology investigation in 1995 had reported an excess of two radiation-induced leukemia cases in an area near a nuclear reprocessing plant, a finding that attracted great interest in France, and which stimulated the need for further investigation. After the publication of its report in 1999, the GRNC was again commissioned to perform, inter alia, a corresponding assessment on the chemical releases of the local nuclear facilities. This second stage is now achieved and has revealed important similarities as well as some important differences between radiological and chemical risk assessments when applied to the specific case of the Nord-Cotentin nuclear facilities. Due to the considerable amount of work and results of the GRNC, the purpose for this article is to briefly describe the main developments of the risk assessment methodology followed by the GRNC in both cases, to detail some of the main results and to identify and explain, at each step, the similarities and the differences. The whole technical documents that support these works are available on the Internet at ?http://www.irsn.fr/nord-cotentin/?.     

Factors affecting farmers' willingness to pay for adopting vegetable residue compost in North China

The random disposal of vegetable residues in north China has become an important obstacle for the sustainable development of vegetable industry. The composting treatment technology has been transformed into organic fertilizer by high temperature fermentation, which has become a widely promoted agricultural clean production technology. However, due to the voluntary nature of farmers' adoption and their reluctance to adopt, this study aimed at assessing the factors that influence their adoption will and evaluate the value of willingness to pay (WTP) for composting technology. Data were collected from 142 respondents through a household survey in Gaocheng District by using structural questionnaire of contingent valuation method (CVM). Some qualitative response models (Probit, Logistic and multiple linear regression models) were applied for examining the main factors influencing the vegetable residue compost adoption and estimating the WTP value. The findings showed that social resource factors play an important role in the respondents' behaviors toward composting technology adoption. The empirical results indeed highlighted that subsidy policy, top dressing time, age, scale, investment of irrigation and net income have significant positive influences on the WTP of compost, while work time and information sources have a negative impact. Government subsidy is a necessary premise for implementing the composting program. The governments should subsidize the remaining 97% of the construction costs to ensure the smooth implementation of composting technology. The findings specifically mentioned that the subsidy object should be the disadvantaged peasant groups with lower household income but more environmentally conscious. This paper is believed to not only assess the technical externality of vegetable residues for the first time but also provide decision reference for policymakers, especially in the background of rapid development of agricultural clean production technology, the accuracy and efficiency of subsidies should be improved.     

Air filled porosity measurements by air pycnometry in the composting process: A review and a correlation analysis

Air filled porosity (AFP) appears as the best measure to determine the available porosity in a composting material or, in general, in an organic matrix. Several methodologies, including theoretical and empirical approaches have been developed to estimate AFP. Among them, air pycnometry has been considered the most suitable and accurate technique to obtain reliable measures of AFP. In this review, the published methodologies to determine AFP by air pycnometry are explained in detail, and the main advantages and disadvantages of such methodologies are discussed. Also, a massive sampling of several organic wastes and mixtures intended for composting has been characterized by air pycnometry, and the theoretical and empirical correlations proposed in literature are compared in terms of accuracy in AFP measurement. Results obtained show that some theoretical correlations are suitable for estimating AFP in the majority of organic wastes studied. However, some waste samples need an experimental determination to obtain a realistic value of AFP.     

The stimulatory effects of surfactants on composting of waste rich in cellulose

The chemical surfactant Tween 80 and biosurfactant rhamnolipid were respectively added to the composting substrate, a mixture of rice straw and bran, and their effects on the composting process were investigated. Samples were analysed for microbial communities of bacteria, actinomycetes and fungi, carboxymethylcellulose hydrolysis (CMCase) and xylanase activities, cellulose and hemicellulose fractions, water-soluble carbon (WSC) contents in the substrates, organic matter contents and pH values during the composting process. The results showed that both Tween 80 and rhamnolipid had slight stimulatory effects on the microbial populations of bacteria, actinomycetes and fungi. In addition, rhamnolipid increased the peak xylanase activity 15% higher than that of the control, while Tween 80 increased the maximum CMCase activity 35% higher than that of the control. As a result of the increased enzyme activities, treatments with Tween 80 and rhamnolipid were of higher WSC contents than the control during the whole composting process. Accordingly, the composting process was accelerated by the surfactants, since the organic matter was decomposed more quickly and the breakdown of cellulose and hemicellulose was better in the treatments with Tween 80 and rhamnolipid.