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.     

The study of the aerobic bacterial microbiota and the biotoxicity in various samples of olive mill wastewaters (alpechin) during their composting process

Five different piles were prepared by mixing olive mill wastewater (alpechin) and alpechin sludge with two bulking agents (cotton waste and maize straw) and two organic wastes with high content of nitrogen (sewage sludge and poultry manure), which were composted by the Rutgers static pile composting system in a pilot plant. The aim of this work was to study the evolution of total nitrogen and different forms of organic matter and evaluate the variation in the aerobic bacterial microbiota present and biotoxicity during the composting process.In piles prepared with alpechin, the use of the maize straw as a bulking agent reduced the nitrogen losses whereas the use of sewage sludge, instead of poultry manure, with cotton waste originated the highest degradation of organic matter. In piles prepared with alpechin sludge a similar evolution of the composting process was observed. There were not great variations during composting in the aerobic bacterial microbiota present in the mixtures. However, the pile prepared with alpechin sludge and maize straw was only one to present bacteria capable of growing in alpechin, and the toxicity study showed that this was only present in the starting mixtures.     

Characteristics of rice straw and sewage sludge as composting materials in Valencia (Spain)

This work supports the idea that composting can be useful for minimizing the rice straw and sewage sludge environmental impact. Several physical, chemical and microbiological properties of these raw materials were analyzed. The characteristics of the rice straw were complementary to those of the sewage sludge for the application of composting. The C/N ratios suitable for a rapid increased in microbial activity were the lowest (17-24). A temperature of 62 degrees C during 48 h removed pathogenic microorganisms from rice straw and sewage sludge mixture. The results obtained in the present work suggested that these materials could be use in the composting process.     

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.     

Comparative analysis of Cryptosporidium, Giardia and indicator bacteria during sewage sludge hygienization in various composting processes

AIMS: To evaluate the suitability of Clostridium perfringens, Escherichia coli and enterococci as indicator organisms for Cryptosporidium and Giardia in treated sludge. METHODS AND RESULTS: Occurrence of Cryptosporidium oocysts and Giardia cysts, detected and enumerated by direct immunofluorescence microscopy, were compared with counts of indicator bacteria during six different sewage sludge hygienization processes, including closed reactor and open windrow composting, and sludge sanitation by quicklime or peat addition. No statistical correlation existed between the counts of indicator bacteria, Cl. perfringens, E. coli, and enterococci and occurrence of Cryptosporidium or Giardia. In sludge end-products, Giardia cysts were detected more frequently than Cryptosporidium oocysts. SIGNIFICANCE OF THE STUDY: Direct analysis is the best method to confirm the presence of (oo)cysts in sludge.     

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.     

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.     

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.     

Lysis and “cryptic” growth in wastewater and sludge treatment processes

The primary objectives in biological wastewater and sludge treatment processes are to procedure a minimum quantity of solid, stable residues and a maximum quantity of carbon dioxide from the organisms present in the process feeds. As far as minimizing solids production in activated sludge type processes is concerned, endogenous activity in the recycled biomass is usually considered to be the most important mechanism. However, increased understanding of the growth characteristics of mixed microbial cultures suggests that lysis and “cryptic” growth are probably dominant mechanisms. For pathogen destruction in treatment processes, death and subsequent lysis of pathogens are clearly events that must be promoted. Here, the kinetics for death, lysis and “cryptic” growth in aerobic wastewater treatment and aerobic sludge stabilization processes are examined.     

The influence of temperature and moisture contents regimes on the aerobic microbial activity of a biosolids composting blend

To understand the relationships between temperature, moisture content, and microbial activity during the composting of biosolids (municipal wastewater treatment sludge), well-controlled incubation experiments were conducted using a 2-factor factorial design with six temperatures (22, 29, 36, 43, 50, and 57 degrees C) and five moisture contents (30, 40, 50, 60, and 70%). The microbial activity was measured as O2 uptake rate (mg g(-1) h(-1)) using a computer controlled respirometer. In this study, moisture content proved to be a dominant factor impacting aerobic microbial activity of the composting blend. Fifty percent moisture content appeared to be the minimal requirement for obtaining activities greater than 1.0 mg g(-1) h(-1). Temperature was also documented to be an important factor for biosolids composting. However, its effect was less influential than moisture content. Particularly, the enhancement of composting activities induced by temperature increment could be realized by increasing moisture content alone.     

On the fate of LAS, NPEOs and DEHP in municipal sewage sludge during composting

The fate of hydrophobic xenobiotic pollutants such as linear alkylbenzene sulfonates (LAS), nonylphenol ethoxylates (NPEO) and di-ethyl-hexyl phthalate (DEHP) during sewage sludge composting was addressed in this work. The experiments were conducted in a fully automated in-vessel autothermal composting system which was fed with a mixture of primary and secondary sludge and manure. The mixture composition was determined to achieve satisfactory humidity, C/N ratio and free air space (FAS). The effect of various parameters, such as the initial xenobiotic concentration, the presence of multiple xenobiotic compounds and the temperature of composting material sustained during the process on the xenobiotics biodegradation kinetics was investigated. It was generally established that significant xenobiotic reduction is achievable through composting under all conditions tested. According to the obtained results, the presence of LAS, NPEO and DEHP even at higher concentrations was not inhibitory to the bioprocess. However, the presence of multiple xenobiotic compounds such as NPEO, NP and DEHP in the sludge can influence LAS removal during LAS composting.     

城市污泥堆肥对栽培基质保水能力和有效养分的影响

盆栽试验表明 ,城市污泥堆肥不仅可以明显提高栽培基质的有效氮、磷含量 ,而且可以增强栽培基质的保水性能和植物的抗旱能力 ,但是栽培基质的萎焉点也随着其用量的增加而增高。因此 ,从保证植物水分供应的角度考虑 ,虽然可以大量地使用城市污泥堆肥 ,但是其用量并不是越多越好 ;当用量超过 75 %时 ,继续增加城市污泥堆肥的比例 ,则植物的吸水能力反而会略有下降。从养分供应和保水性能等角度综合考虑 ,采用经过堆肥化处理的城市污泥作为植物栽培基质 ,是城市污泥资源化和无害化的可行途径     

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.     

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.     

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.     

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.     

Effects of a bulking agent on the reaction rate of thermophilic sewage sludge composting

The effects of a bulking agent on the reaction rate of sewage sludge composting was investigated quantitatively. Larger amounts of rice husks added as the bulking agent yielded a higher CO₂ evolution rate and a larger number of thermophiles per unit dry mass of raw sludge. The specific CO₂ evolution rate estimated for each thermophile was almost the same, however, irrespective of the mixing ratio of rice husks. Since the calculation showed that the composting solid particles were aerobic, we suggest that the addition of a bulking agent may increase air-solid interfaces where microorganisms can selectively grow to make colonies.     

The occurrence of Candida Albicans in Lake Ontario bathing beaches.

There are inherent weaknesses associated with currently used bacterial fecal pollution indicator systems. Fecal pollution indicator data would be more meaningful if supplemented with information relating to the occurrence of pathogens in recreational water. Through surveys of four bathing beaches on Lake Ontario, it was established that the opportunistically pathogenic yeast Candida albicans occurs in near shore waters. The beaches surveyed could be differentiated on the basis of bacterial fecal pollution indicator levels and numbers of the pathogens C. albicans and Pseudomonas aeruginosa. The occurrence of C. albicans and P. aeruginosa appeared to be related to elevated fecal pollution indicator levels. Maximum numbers of all parameters were observed in July and August in association with peak bather loads at the beaches. In only one instance does the data suggest that a beach was subjected to human fecal contamination.     

Increased frequency of drug-resistant bacteria and fecal coliforms in an Indiana Creek adjacent to farmland amended with treated sludge

Many studies indicate the presence of human pathogens and drug-resistant bacteria in treated sewage sludge. Since one of the main methods of treated sewage disposal is by application to agricultural land, the presence of these organisms is of concern to human health. The goal of this study was to determine whether the frequency of drug-resistant and indicator bacteria in Sugar Creek, which is used for recreational purposes, was influenced by proximity to a farmland routinely amended with treated sludge (site E). Surface water from 3 sites along Sugar Creek (site E, 1 upstream site (site C) and 1 downstream site (site K)) were tested for the presence of ampicillin-resistant (Amp(R)) bacteria, fecal and total coliforms over a period of 40 d. Site E consistently had higher frequencies of Amp(R) bacteria and fecal coliforms compared with the other 2 sites. All of the tested Amp(R) isolates were resistant to at least 1 other antibiotic. However, no isolate was resistant to more than 4 classes of antimicrobials. These results suggest that surface runoff from the farmland is strongly correlated with higher incidence of Amp(R) and fecal coliforms at site E.     

Enhancement of dry anaerobic batch digestion of the organic fraction of municipal solid waste by an aerobic pretreatment step

The start-up of the dry anaerobic batch digestion by the BIOCEL-concept of the organic fraction of municipal solid waste (MSW) is unbalanced when a methanogenic inoculum (digested sewage sludge) is added to a total solids concentration of 35%. The unbalanced conditions are the result of the rapid degradation of easily-degradable compounds which are present in the organic fraction. Enhancement of the first start-up of the dry batch digestion was tried by applying an aerobic partial-composting step. By this aerobic treatment the easily degradable compounds are removed. After the composting step the anaerobic digestion will be limited by the conversion of the ligno-cellulose part of the organic fraction. It appeared that at least 19·5% of the volatile solids (VS) should be converted during the aerobic composting period before acid formation in the digestion was in balance with the methane formation. This amount of aerobically degraded VS means a 40% loss of potential biogas. The loss of a part of the biogas is a major drawback to the partial composting as a method for enhancing the start-up of the dry anaerobic digestion. A shorter composting period which is combined with another start-up method might be a feasible method to decrease the energy input of the dry digestion process.