Determination of the Effect of Aeration Rate on Composting of Vegetable–Fruit Wastes

In this study, it was aimed to determine the effect of various aeration rates on composting to supply the optimum aeration rate for a successful and economic composting. For this aim, vegetable–fruit wastes (VFW) were composted at various aeration rates (0.37, 0.49, 0.62, 0.74, 0.86, and 0.99 L/min kg VS) and moisture, temperature, pH, electrical conductivity, C/N, and cellulose were investigated. Moistures of the reactor that had the highest aeration were generally lower than those of the others. Reactor that had the lowest aeration reached thermophilic phase earlier than the others and stayed more days. This situation was opposite for the reactor that had the highest aeration. pH variations with aeration rates were not significant. Although electrical conductivity did not differ significantly with aeration rates, at the beginning of the thermophilic phase it generally increased with the increase in aeration. The highest C/N reduction was observed in the reactor that had an aeration of 0.62 L/min kg VS. The final cellulose contents were close to each other. It could be said that aeration rates used were efficient on composting of VFW. Taking the C/N into account which is the parameter of the indicator of the stabilization in composting, it could be said that the optimum aeration rate for forced aerobic composting of VFW was 0.62 L/min kg VS.     

Role of Humification Processes in Recycling Organic Wastes of Various Nature and Sources as Soil Amendments

Recycling the large amounts of organic wastes produced by agriculture, forestry, urban and industrial activities as soil, organic amendments are the most popular and efficient option for avoiding their dispersion in the environment and restoring, maintaining, and/or improving the content of soil organic matter. Chemical stability and biological maturity are two important factors for the successful use of organic wastes in agriculture with limited risk for the surrounding environment. Stabilization and maturation of raw organic wastes inherently imply the achievement of an extensive humification, that is, a wide conversion of easily degradable organic matter to refractory organic compounds that resemble native soil humic substances (HS). Soil HS are the most important components of soil organic matter responsible of several soil functions and processes. As a consequence, the amount and quality of HS‐like fractions in any organic amendment are believed to be of primary importance for its agronomic efficacy, environmental safety and economic value. The first part of this review focuses on the chemical and physico‐chemical changes occurring in the humic substances (HS) ‐like fractions of organic wastes of various nature and sources subjected to common treatment processes aimed at producing environmentally‐safe soil amendments with beneficial agronomic properties. The second part discusses the composition, structure, and chemical reactivity of the HS‐like components in organic amendments of various origins and nature, and their effects on native soil HS. The review concludes by highlighting the need for innovative research targeted mainly to achieve a better fundamental understanding of the molecular structure and reactivity of soil HS and HS‐like fractions in organic amendments, the mechanisms of HS formation and transformations in the natural environment and during the treatment processes of raw organic wastes, the interactions with metals and organic xenobiotics, and the direct physiological effects that HS may exert on plants.     

Improving the Quality of Municipal Solid Waste Compost by Using Expanded Perlite and Natural Zeolite

The scope of this study was to investigate the effects of natural zeolite and expanded perlite on the quality of municipal solid waste compost. Various ratios of the materials were added as supplements to the organic fraction of municipal solid waste. These applications were periodically compared with an untreated control process. The results obtained from experimental studies clearly showed that municipal solid waste collected from the metropolitan city center of Samsun, Turkey could not be composted without any additions due to the very high moisture content, which reached up to 75–80%. In the untreated control process, thermophilic temperatures were not supported during the composting. In this system, ammonia and other odors became a problem because of the high pH levels, and the electrical conductivity was too high for aged compost. However, the addition of natural zeolite and expanded perlite had a positive affect on the quality of the final compost. Natural zeolite trapped ammonium and reduced nitrogen losses from the compost. Expanded perlite held excess moisture and supported improved aeration. The results also indicated that the use of natural zeolite together with expanded perlite in municipal solid waste composting processes produced mature and stable compost.     

Common sense principles governing potable water recycling in the southwestern US: Examining subjectivity of water stewards using Q methodology

The potential to supplement potable water supplies with highly treated municipal wastewater, or sewage, is of increasing interest to water planners in many parts of the world. Most of the current social science focuses on public acceptance, however there is a relative lack of research that explores the subjectivity of people who are involved with water recycling or water planning. This study draws on Gramscian theories of governance and Q Methodology to analyze common sense principles that are held by water stewards who currently govern potable water reuse in the southwestern United States. Two competing perspectives emerged from the analyses, which I label neosanitarian and ecosanitarian. Drawing upon tenets established in the Progressive Era, neosanitarians believe that use of recycled water is an appropriate way to expand urban drinking water supplies. Drawing upon tenets established in ecology, ecosanitarians are not opposed to potable water recycling, however they are also interested in radical alternatives to the sanitary status quo. For example, neosanitarians favor advanced wastewater treatment, while ecosanitarians prefer composting toilets and preventative actions. Differences between the common sense views pivot on ideas about the most appropriate technology but also reflect contested visions of ideal society.     

Reduction of Ammonia,Hydrogen Sulfide,and Short‐Chain Fatty Acids Emission during the Sewage Sludge Composting

The effect of mature compost (MC) used as a bulking agent on ammonia, hydrogen sulfide, and short‐chain fatty acids emission reduction during sewage sludge (SS) composting process was studied in this paper. Three types of mixtures, single SS, SS + wood chips (SS + WC), and SS + MC, were composted in a laboratory reactor. Among the different treatments, decrement rates of NH₃ emission (based on initial TN) from SS to SS + MC and SS + WC to SS + MC were 63 and 59%, respectively. The H₂S concentration ranged from 0.759 to 1.140 mg m^?3 for SS, from 0.075 to 0.455 mg m^?3 for SS + WC, and from 0.075 to 0.425 mg m^?3 for SS + MC and the short‐chain fatty acids (C₂–C₅) concentration ranged from 0.10 to 1.00 ppm for SS, from 0.10 to 1.50 ppm for SS + WC, and from 0.10 to 0.80 ppm for SS + MC. In addition, the temperature apparently, as well as the thermophilic stage, was also elevated by bulking agent addition, especially by the MC addition. The denaturing gradient gel electrophoresis analysis indicated that there was more diversity of the bacterial community during the SS + MC process. According to these results, MC was a suitable bulking agent for reduction ammonia, hydrogen sulfide, and short‐chain fatty acids emission during the SS composting.