城市污泥强制通风堆肥过程中的生物学和化学变化特征

采用间竭式强制通风堆肥法进行的肥堆体积约4m3,堆肥时间为53d的污泥堆肥试验表明,堆肥的第2天即达高温阶段(≥55℃)并能保持8d,平均最高温度达68℃,局部温度达74℃.粪大肠杆菌由开始时的1.41×105个·g-1降至试验结束时的2.32×101个·g-1.污泥堆肥过程中挥发性固体,总有机C、水溶性有机C、固体有机 C/N比和水溶性有机 C/有机 N比下降明显,而 N、P及重金属含量有所升高.随着堆肥的进程,在前1周堆肥过程中产生的氨氮大幅下降,硝酸盐含量随之升高.相应地,pH在第1周内升高,随后降低.堆肥40d左右,水芹(Lepidiumsativum L.)种子发芽指数即可达 80%.综合堆肥过程中堆温和化学与生物学变化特点,表明污泥堆肥在40d左右基本上接近腐熟,50d后达到完全腐熟.产品外观呈黑褐色,蓬松,无明显异味.     

Determining thermal inactivation of Escherichia coli O157:H7 in fresh compost by simulating early phases of the composting process

A three-strain mixture of Escherichia coli O157:H7 was inoculated into fresh dairy compost (ca. 10(7) CFU/g) with 40 or 50% moisture and was placed in an environmental chamber (ca. 70% humidity) that was programmed to ramp from room temperature to selected composting temperatures in 2 and 5 days to simulate the early composting phase. The surviving E. coli O157:H7 population was analyzed by direct plating and enrichment. Optimal and suboptimal compost mixes, with carbon/nitrogen (C/N) ratios of 25:1 and 16:1, respectively, were compared in this study. In the optimal compost mix, E. coli O157:H7 survived for 72, 48, and 24 h in compost with 40% moisture and for 72, 24, and 24 h with 50% moisture at 50, 55, and 60°C, respectively, following 2 days of come-up time (rate of heating up). However, in the suboptimal compost mix, the pathogen survived for 288, 72, and 48 h in compost with 40% moisture and for 240, 72, 24 h in compost with 50% moisture at the same temperatures, respectively. Pathogen survival was longer, with 5 days of come-up time compared with 2 days of come-up. Overall, E. coli O157:H7 was inactivated faster in the compost with 50% moisture than in the compost with 40% at 55 and 60°C. Both moisture and come-up time were significant factors affecting Weibull model parameters. Our results suggest that slow come-up time at the beginning of composting can extend pathogen survival during composting. Additionally, both the C/N ratio and the initial moisture level in the compost mix affect the rate of pathogen inactivation as well.     

The kinetics of nicotine degradation,enzyme activities and genotoxic potential in the characterization of tobacco waste composting

This study aimed to determine nicotine biodegradation and the genotoxic potential of nicotine and its degradation products during the process of tobacco waste composting. Composting was carried out using two methods, i.e. the addition of 20% (bioreactor A) or 40% tobacco wastes to sewage sludge (bioreactor B) and control – sewage sludge (bioreactor C). Wheat straw was used as a structure-forming material. As a result of composting the contents of C and N in the bioreactors changed, the C:N ratio in bioreactor A changed from 22.8 to 13.00, and that in bioreactor B changed from 23.5 to 12.00. After composting, the biodegradation rate of nicotine was 78% in bioreactor A and 80% in bioreactor B, respectively. Using the Ames test it was shown that the composts produced did not exhibit mutagenicity.     

Changes in physical,chemical and microbial parameters during the composting of municipal sewage sludge

Changes in physical, chemical and microbial parameters were investigated during the composting of municipal sewage sludge. Raw sewage sludge (30% dry matter) was mixed with compost from sewage sludge (85% dry matter) in 3:1 ratio (v/v). The mixture was divided into 4 windrows which were composted under the same conditions except the turning factor. The turning was every 7, 10, 15 days and according to the temperature which must be (55–65°C) for windrow 1 (W1), windrow 2 (W2), windrow 3 (W3) and windrow 4 (W4), respectively. Water was added to adjust the moisture content (40–60%). The composting process consisted of 2 periods; fermentation (12 weeks) and maturation (4 weeks). The results showed that the temperature reached the maximum after 12 weeks for W1 and 11 weeks for W2, W3 and W4 and then decreased. The final compost was nearly odourless and black, especially in case of W4. The general trend indicates a decrease in organic matter, organic carbon and nitrogen (N), whereas ash, potassium (K) and phosphorus (P) increased and consequently C/K and C/P ratios decreased. There was a slight increase in C/N ratio. The pH increased and then decreased to near neutrality at the end. The mesophilic bacteria increased during the fermentation period and decreased after that, whereas the thermophilic ones increased with increasing of temperature, decreased after 2 weeks and increased again during the fermentation period and then decreased. The mesophilic and thermophilic fungi were present during the first week and disappeared after that. The final compost was pathogens-free as indicated by the counts of coliforms and Salmonella.     

Organic matter transformations and kinetics during sewage sludge composting in a two-stage system

The use of different proportions of rape straw and grass as amendments in the composting of dewatered sewage sludge from a municipal wastewater treatment plant was tested in a two-stage system (first stage, an aerated bioreactor and second stage, a periodically turned windrow). The composition of feedstock affected the temperature and organic matter degradation in the bioreactor and the formation of humic substances, especially humic acids (HA), during compost maturation in the windrow. The total HA content (the sum of labile and stable HA) increased according to first-order kinetics, whereas labile HA content was constant and did not exceed 12% of total HA. Δlog K of 1.0–1.1 indicated that HA was of R-type, indicating a low degree of humification. Temperature during composting was the main factor affecting polymerization of fulvic acids to HA and confirmed the value of the degree of polymerization, which increased only when thermophilic conditions were obtained.     

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.     

Characterization of natural organic matter (NOM) derived from sewage sludge compost. Part 1: chemical and spectroscopic properties

In this study changes in the properties of natural organic matter (NOM) were studied during composting of sewage sludge in a laboratory experiment using the pile method. Typical physicochemical parameters were measured during 53 days of composting including humic fractions. The effects of humification on the molecular properties of humic acids (HA) were investigated by 13C CP/MAS NMR spectroscopy. On the basis of chemical analyses, 53 days of composting sewage sludge with structural material can be divided into three phases: (i) domination of rapid decomposition of non-humic, easily biodegradable organic matter (two to three weeks), (ii) domination of organic matter humification and formation of polycondensed, humic-like substances (the next two weeks), (iii) stabilization of transformed organic material and weak microbial activity. Spectroscopic characterization (13C NMR) of compost humic acids reveals changes in their structures during maturation. The changes are highly correlated with the processes taking place in bulk compost.     

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.     

The modelling of combined strategies to achieve thermophilic composting of sludge in cold region

Low ambient temperature presents a significant technical challenge for efficient operation of the composting facility located in cold region. In this study, mathematical model was used as a tool to develop the operational strategy to accomplish thermophilic composting of sewage sludge in the cold-climate environment. The correlations between composting temperature, water volatilization, heat loss rate, organics degradation and ambient temperature, feedstock temperature, sludge moisture and aeration rate were predicted and evaluated by using the numerical simulation method. The feasibility of optimizing air supply, adjusting feedstock moisture and elevating starting temperature in the low temperature surroundings was investigated. The results obtained from both mathematical modelling and pilot-scale composting experiments demonstrated that the combined strategies of the three approaches could preliminarily achieve material drying, pathogen inactivation and organics stabilization within 20 days at the ambient temperature as low as −24 °C. However, it seems difficult for anyone of these approaches to meet the requirement of thermophilic composting, independently.     

Estimation of phosphorus bioavailability from composted organic wastes

Sewage sludge derived from municipal sewage treatment plants is an important source of macronutrients, micronutrients and organic matter. For this reason composting of sewage sludge, along with combustion and co-combustion, is a new management priority in Poland. In this study six composts of different origin and composition were evaluated in terms of their abundance in phosphorus, because it is an essential nutrient for all living organisms. Analyses were conducted on the samples at the initial and at the maturation phase of composting. The bioavailability of phosphorus was estimated on the basis of amounts of the nutrient in isolated fractions using the sequential extraction method. First of all quantitative changes of the total nutrient content and its amounts in separated fractions were dependent on the mixture composition. Irrespective of compost type, 34.5–75.0% of the total amounts of phosphorus were found in hardly available combinations (Fr. III), while available phosphorus forms (Fr. I) accounted for only 6.6–21.6%. As a result of composting together different organic wastes an increase was observed both in the total content and the amounts of this nutrient in separated fractions. This phenomenon was observed particularly in composts with smaller levels of sewage sludge (30–40%), characterised by rapid organic matter decomposition, which was indicated by higher bioavailable amounts of phosphorus. Under such conditions the content of P ranged between 3.68 and 7.4 g kg^?1. In comparison to the labile pool of P obtained for matured composts C5 and C6 (65 and 75% of sewage sludge in their composition) amounting to 2.45–3.0 g kg^?1 the above values were considerable. Bioavailable phosphorus contents potentially introduced to soil with composts doses calculated at 170 kg total N/ha/yr ranged from 69.8 to 80.2 kg for compost with the lowest share of sewage sludge and from 11.2 to 20.7 kg for compost with the highest share of sewage sludge.     

Influence of humic substances on bioavailability of Cu and Zn during sewage sludge composting

Influence of humic substances (HS) on bioavailability of Cu and Zn was characterized during 120 days co-composting of sewage sludge and maize straw. At the initial stage of composting, Cu and Zn in sewage sludge were released as organic matter was degraded, and water soluble Cu and Zn increased markedly. Water soluble Cu and FA content decreased after 21 days whereas water soluble Zn increased during the whole process. Both HA-Cu and HA-Zn were significantly and positively correlated with HA and H/F, respectively. At the end of composting, the distribution coefficients of HA-Cu and HA-Zn reached 27.50% and 3.33% respectively with HA-Cu/HA-Zn ratio increased from 1.29 to 2.73. The results suggest that Cu combined with HA more strongly than Zn, and composting treatment could decrease bioavailability of Cu markedly.     

Effect of initial physical characteristics on sludge compost performance

To develop an active microbial activity quickly developing stabilizing thermophilic temperatures during the composting of wastewater sludge, the bulking agent (BA) plays a major role in establishing the recipe structure, exposed particle surface area and porosity. To optimize the biodegradation of a sludge compost recipe, the objective of this paper was to study the effect and interaction of initial moisture content (MC) and BA particle size distribution. Three 300 L insulated laboratory composters were used to treat two series of ten (10) recipes with different combinations of MC and BA particle size distribution. Using a to wastewater sludge to BA dry mass ratio of 1/6, the ten (10) recipes were repeated using two BA, residues recycled from a commercial sludge composting plant and crushed wood pallets. Each four week trial monitored O₂ uptake, temperature, compost consolidation and airflow distribution. The Central Composite Factor Design method produced a model from the results estimating the impact of a wider range of MC and BA particles size distribution. The MC directly affected the total O₂ uptake and therefore, organic matter biodegradation. The BA particle size distribution influenced compost consolidation with a MC crossed effect. Both BA particle size distribution and MC influenced compost airflow dispersion. Composting was optimized using the BA consisting of recycled green waste residues with particle size of 20–30 mm and a 55% MC. The predictive models suggested the need for further optimization of sludge and wood residue composting recipe.     

Ecophysiological Responses of Plants After Sewage Sludge Compost Applications

Composting is one of the most appropriate methods to recycle sewage sludge. Sewage sludge compost is a suitable solution for improving the quality of barren soil at landfill. Therefore, it is important to investigate the effects of sewage sludge compost on plants. Different compost application methods (mixing and scattering over reclaimed soil) on sawtooth oak (Quercus acutissima) and Japanese red pine (Pinus densiflora) have been tested. The application of sewage sludge compost markedly increased soil moisture and nitrogen content. Compost treatments resulted in significant increases in both plant height and biomass as compared to controls. Compost treatments led to a significant increase in the N content of plant leaves. Compost treatments resulted in significant increases in the chlorophyll content and photosynthetic rates of the plants. The scattering of compost over reclaimed soil (compost 2) resulted in lower total antioxidant activity and superoxide dismutase activity than mixing the compost with the reclaimed soil (compost 1), or in the control treatment. Since the growth rates, N content, and photosynthetic rates in compost 2 treatment were not markedly different from compost 1 treatment, it (compost 2) would be a better application method from both an ecological and economic perspective.     

Physical and Chemical Correlates of Microbial Activity and Biomass in Composting Municipal Sewage Sludge

Various physical and chemical parameters were monitored to evaluate their influence on the microbial communities present in composting municipal sewage sludge. Temperature, moisture content, depth, pH, protein content, total nitrogen, total carbon, lipid phosphate biomass, and the rates of microbial incorporation of substrates into lipids were measured at several times throughout the 17- to 19-day composting runs. Temperature was found to have the most consistent and dramatic effect on microbial activity and biomass. When temperatures exceeded 55 to 60°C, microbial activity fell dramatically, usually by more than 1 order of magnitude. Microbial activity was generally greatest in samples taken from the 35 to 50°C areas of the composting piles. Changes in the composition of the compost over time included increased pH, increased protein content, and decreased total organic content. The changes in these parameters appeared to reflect the microbial activity and biomass present. The results of this study indicate that the rate of composting may best be optimized by controlling the composting temperatures, provided that the other parameters fall within reasonable limits in the starting material.     

Characteristics of Mesophilic Bacteria Isolated during Thermophilic Composting of Sewage Sludge

The degree of inactivation by UV irradiation was different between vegetative cells and spores of bacteria isolated from sewage sludge composting at 60°C. By using this property, a method to estimate the spore ratio of a mixture of vegetative cells and spores was presented. This UV irradiation method was applied to the estimation of the spore ratio of sewage sludge compost samples collected at several stages of composting. The spore ratio of mesophilic bacteria in the samples obtained at the thermophilic stage of 60°C was 40% at most. The vegetative form of mesophilic bacteria showed a thermotolerance property at 60°C by forming colonies but showed no respiratory activity at that temperature.     

Co-composting of sewage sludge:fats mixtures and characteristics of the lipases involved

Co-composting of sewage sludge and animal fat mixtures was studied in order to determine the possibility of using this technology to recycle fat-enriched wastes. A maximum fat content of 30% in fat:sludge mixtures is recommended to achieve the international sanitation requirements on compost quality and to avoid an excessive thermophilic composting time. Under these conditions a fat content reduction of 85% was achieved. Biological activity was highly dependent on the moisture content as shown by the respiratory quotient values. Moisture content is a critical control factor because of the hydrophobic nature of fats and should be maintained above 40% in the composting of fats. Biological indices of the compost obtained after 69 days of process (maturity grade: IV; respiration index: 1.1 mg O₂ g OM⁻¹ h⁻¹) indicated a high stability and maturity degree of the material. Lipases responsible for fat hydrolysis were monitored during the composting process and a sample from the thermophilic period was characterized in terms of stability in front of pH and temperature. Optimal conditions for lipase stability were found at 38.3 °C and pH 7.97, however, the maximum lipolytic activity was observed at thermophilic temperatures. Lipases from the thermophilic period were purified by anion exchange chromatography and visualised by SDS-PAGE. Two major bands were observed at molecular weights of 29 and 62 kDa. These bands could not be identified precisely by N-terminal sequence analysis.     

The influence of composting on the fertilizing value of an aerobic sewage sludge

The influence of composting on the fertilizing value of an aerobic sewage sludge and its action on ryegrass was studied. Soil P and K contents, cation-exchange capacity (CEC) and CEC/total organic carbon incresed with composting, while the percentage of phytotoxic substances diminished. The compost provided useful quantities of organic matter and macronutrients. The addition of uncomposted waste to the soil initially had a depressive effect on yield which disappeared after a period of incubation of this material in the soil, whereas the application of a mature compost produced yields superior to those in the control treatment.     

Nitrogen transformation during thermophilic composting

Nitrogen transformation of sewage sludge composting without or with rice husks as a bulking agent was investigated. When rice husks were added, nitrogen loss was reduced. Garbage and fish residue were also composted to compare the ammonia volatilization with sewage sludge. Conversion of carbon and that of nitrogen were correlated with the change of the C/N ratio of initial composting materials. Sawdust and bark were found to be efficient bulking agents to reduce the loss of nitrogen due to volatilization of ammonia during composting.     

湿度对堆肥理化性质的影响

水分是堆肥微生物生命活动的基础 ,也是堆肥中重要的工艺控制参数。弄清湿度对堆肥微生物及理化性质的影响 ,对于优化堆肥工艺参数、提高堆肥效率、降低投资和运行成本具有重要意义。综述了堆肥湿度研究的动态 ,指出了当前研究中存在的问题 ,并提出了未来的研究方向。大量的研究表明 ,湿度低于 4 5 %或高于 6 5 %都不利于堆肥处理。湿度太高会导致堆料的压实度增加、FAS减少、透气性能降低 ,从而导致堆体内氧气供应不足、堆肥升温困难、有机物降解速率降低、堆肥周期延长。湿度过低 ,水分会限制堆肥微生物的新陈代谢 ,导致微生物活性下降、堆肥腐熟困难。由于鼓风、散热、水蒸发等会使堆体内存在湿度的空间变异 ,也会降低堆肥效率和堆肥产品的质量。另外 ,堆肥湿度还影响堆肥的保肥能力。由各文献得出结论 ,堆肥的最佳湿度范围一般为 5 0 %～ 6 0 %左右     

A new method for conservation of nitrogen in aerobic composting processes

Several factors, such as pH, C/N ratio, temperature, mixing and turning, and aeration rate, could affect the loss of ammonia in composting reactions. Substantial loss of ammonia can reduce the nutrient value of the compost product and may lead to a severe odor problem in the composting facility. A new method for conservation of ammonia in composting was proposed and tested in this study. The ammonia being produced during the composting was precipitated into struvite crystals by addition of Mg and P salts. Ammonia volatilization was greatly reduced by this method and it also contributed to a remarkable increase in total ammoniacal-N (TAN) content in the compost, reaching up to 1.4% of dry mass. This value of TAN content was 3-5 times higher than that in normal compost. The scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analyses confirmed the formation of struvite crystals in the aerobic composting process.