Sawdust and natural zeolite as a bulking agent for improving quality of a composting product from anaerobically stabilized sewage sludge

This study has dealt with the production of compost from dewatered anaerobically stabilized primary sewage sludge (DASPSS) and sawdust (SWD). SWD is added in order to increase the humic substances in the final product. The DASPSS is mixed with clinoptilolite (Cli), which is used as a bulking agent at 20% w/w, and the mixture is amended with sawdust at 10%, 30% and 40% (w/w). The final results have indicated that by increasing the sawdust concentration in the initial mixture, the humic substances in the final product increase too. The natural zeolite that was added in the initial mixture takes up a significant amount of heavy metals. In order to observe the maturity of the final product, the germination index is used in oat cultivation. The results indicate that the substrate appears to be non-phytotoxic after 75 d of maturity. Also, in order to estimate the metal leachability of the final compost product, the generalized acid neutralization capacity procedure is applied, and it is found that by increasing the pH values, the heavy metal concentrations decrease.     

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.     

Microbial community structure changes during bioremediation of PAHs in an aged coal-tar contaminated soil by in-vessel composting

The microbial community structure changes of an aged-coal-tar soil contaminated with polycyclic aromatic hydrocarbons (PAHs) were investigated during simulated bioremediation at the laboratory-scale using an in-vessel composting approach. The composting reactors were operated using a logistic three-factor factorial design with three temperatures (T=38, 55 or 70 °C), four soil to green-waste amendment ratios (S:GW=0.6:1, 0.7:1, 0.8:1 or 0.9:1 on a dry weight basis) and three moisture contents (MC=40%, 60% or 80%). Relative changes in microbial populations were investigated by following the dynamics of phospholipid fatty acid (PLFA) signatures using a ¹³C-labeled palmitic acid internal standard and sensitive GC/MS analysis during in-vessel composting over 98 days. The results of this investigation indicated that fungal to bacterial PLFA ratios were significantly influenced by temperature (p<0.05), and Gram-positive to Gram-negative bacterial ratios were significantly influenced by temperature (p<0.001) and S:GW ratio (p<0.01) during in-vessel composting. Additionally, the Gram-positive to Gram-negative bacterial ratios were correlated to the extent of PAH losses (p<0.005) at 70 °C.     

The application of an life cycle inventory (LCI) model for solid waste disposal systems in malaysia

This paper discusses the application of an LCt model for solid waste management systems in Malaysia. The model was used to analyze the environmental and economic impacts of municipal waste management systems in Malaysia. In the first part of the study, the LCI model was adapted to analyze waste management systems of four selected cities: Kuala Lumpur and Penang to represent urban areas; Seremban to represent moderately urban areas and Muar to represent rural areas. The results have shown that Kuala Lumpur and Penang had greater Global Warming Potential (GWP) and the costs spent on the solid waste management were also higher as compared to that in suburban areas. In the second part of the study, a detailed evaluation was carried out by analyzing the implication of introducing incineration and composting into the solid waste management system, and the results were compared with the current system, i.e. 100 % landfilled. The relative GWP was lower for incineration, but the cost was extremely high. The results also showed that the final solid waste to be disposed to landfills and the impact due to water emissions could be reduced significantly when incineration and composting were introduced.     

Characterisation of biological properties of co‐composted Baltic seaweeds in germination tests

Large quantities of green seaweed, probably due to eutrophication, are found in the Baltic Sea, as well as on the beach. The tourist attractiveness of the seaside resorts is therefore reduced. The aim of this study was to find the method of the utilization of this algal biomass into fertilizers. Algae, collected from the Baltic Sea, were co‐composted with sawdust and quail manure in order to produce natural fertilizer. From the compost, algal extract was additionally produced that can act as a plant growth biostimulant. The compost and extract were biologically evaluated by the determination of the growth and multielemental composition of garden cress (Lepidium sativum) in germination tests. Additionally, the odour emissions during composting process were investigated. It was found that the dry biomass was comparable in all examined groups (compost, extract, distilled water). The average length of plants in the group with compost was 14.5% higher than in the group with the extract (difference not statistically significant). There has been observed a positive effect of the addition of compost on the content of micro‐ and macronutrients in the biomass of the cultivated plants, especially boron, calcium, iron and silicon. The averaged odour concentrations measured from the compost and extract samples were very low and reached the values of 8 and 24 ou_E/m³, respectively. According to the obtained results, by composting of seaweeds it is possible to produce a valuable organic fertilizer, which is the method of valorisation of this biomass.     

堆肥中木质素降解微生物对腐殖质形成的作用

堆肥化是处理有机固体废物的主要方法之一。但传统堆肥法存在历时长、肥效低等问题 ,因此加速腐殖化进程可提高堆肥效率和堆肥质量。综述了堆肥中降解木质素的微生物种类的腐殖质的组成 ,介绍了木质素降解与腐殖质形成的关系 ,最后阐述了堆肥中各木质素降解微生物对腐殖质形成的作用。     

辽西褐土施肥及养分循环再利用中长期试验Ⅲ.磷和氮在堆腐过程中的循环率及有机肥料中养分利用率

9年的试验结果表明 ,农产品中N、P经堆腐后损失率平均为 30 % .在丰产条件下 ,6 0 %的收获产品直接堆腐回田 ,可循环回田的养分量为N 5 5～ 70kg·hm-2 、P 9～ 11kg·hm-2 ,相当于这一系统中每年化肥N用量的 37%～ 4 7%和P肥用量的 36 %～ 4 4 % .有机肥料中N和P的表观利用率随施肥年限延长而有增长趋势 ,表明有残效叠加效应存在 .有机肥料中N和P的当季表观利用率 8年平均分别为 2 3%～5 0 %和 37%～ 6 5 % .通过此项研究可以证明 ,农业生态系统养分的循环再利用是保持土壤肥力 ,提高养分利用效率 ,减少化学肥料消费的重要措施 .     

不同类型原油污染土壤生物修复技术研究

对不同类型原油污染土壤在实用规模的预制床上采用堆制技术进行生物修复 .通过投加肥料、菌剂、控制水分和pH ,可使微生物获得较好的生态环境 .当稀油、高凝油、特稠油和稠油污染的土壤中原油总量为 2 5 .8～ 77.2 g·kg-1土时 ,经过近 2个月的运行 ,石油总量的去除率可达 38.37%～ 5 6 .74 % .石油中芳烃、沥青和胶质混合物是制约石油快速降解的主要因素 .在处理过程中筛选出石油降解的优势菌株 ,其中有 6株真菌、6株细菌和 1株放线菌 .研究结果为石油污染土壤异位生物修复技术实用化提供了理论依据 .     

城市污泥与稻草堆肥中邻苯二甲酸酯（PAEs）的研究

将广州城市污泥与稻草进行翻堆、接菌-翻堆、连续通气和间歇通气4种方式的堆肥,应用GC／MS技术对堆肥中6种属于USEPA优控污染物的邻苯二甲酸醇化合物(PAEs)进行分析,探讨堆肥产物中PAEs的含量分布以及不同方式堆肥对PAEs的降解效果,结果表明,4种方式堆肥中PAEs总含量(∑PAEs)在9．815～17．832mg·kg^-1之间,依次为翻堆(17．832mg·kg^-1)>接菌-翻堆(13．927mg·kg^-1)>间隙通气(10．765mg·kg^-1)>连续通气(9．815mg·kg^-1),堆肥中PAEs以邻苯二甲酸正二辛酯(DhOP)为主,占∑PAEs的82．2％～89．696,不同方式堆肥中∑PAEs的降解率为连续通气(45．71％)>间隙通气(40．4696)>接菌-翻堆(22．97％)>翻堆(1．3796)(平均降解率为27．63％),其中邻苯二甲酸二乙醇(DEP)、邻苯二甲酸正二丁酯(DnBP)和邻苯二甲酸丁基苄基酯(BBP)的降解率分别为95．7696～98．6896、79．5696～99．46％和87．42％～98．42％;但邻苯二甲酸二甲酯(DMP)和邻苯二甲酸正二辛酯的含量反而增加,邻苯二甲酸(2-乙基己基)酯(DEHP)在所有堆肥中均未检出。     

Design and application of a pre-composting test step to determine the effect of high fat food wastes on an industrial scale in-vessel composting system

The high fat content in food wastes was suspected to inhibit an industrial in-vessel composting process from reaching the European Union Animal By-Product Regulation (composting temperature >70 °C for 1 h). The aim of this study was to design a test step to guide the mixing ratio of food waste to green waste to meet the regulation. A 15-compartment composting unit was designed to contain the compost mixes. Sausage and cheese wastes were mixed with green waste at 1:1; 1:2; 1:3 and 1:4 ratios by wet weight volume. Only the sausage waste mix ratio of 1:4 gave an average temperature of 70 °C for at least 1 h after 2 days of composting (fat content - 17%; C: N ratio - 8.6). All the cheese waste mixes did not reach 70 °C after 15 days of composting. This study demonstrated that using a simple pre-composting test step could reduce the chances of process failure during industrial composting. Although both sausage and cheese wastes are high in fat, they performed very differently in the composting process. Two linear equations were fitted to model the impact of these wastes on the maximum composting temperature.