Assessment of co-composting of sewage sludge, woodchips, and sawdust: feedstock quality and design and compilation of co
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RESEARCH ARTICLE
Assessment of co-composting of sewage sludge, woodchips, and sawdust: feedstock quality and design and compilation of computational model Somayeh Golbaz 1 & Mir Zaman Zamanzadeh 1 & Hasan Pasalari 2,3 & Mahdi Farzadkia 2,3 Received: 22 December 2019 / Accepted: 12 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Composting process of sewage sludge requires a preprocessing step in order to prepare the appropriate mixture of dewatered sludge (Xs) with amendment (Xa), bulking agent (Xb), and/or recycled materials (Xr). This research aimed to develop a novel mathematical model for finding an optimal mixture ratio of dewatered sludge with the aforementioned influencing elements on co-composting process. Seven feasible scenarios were presented and the best one was selected in viewpoint of technical and economic perspectives. The optimum mixture was prepared and its quality was evaluated in the terms of physical, chemical, and microbial characteristics. The optimum mixture was loaded in an aerated static pile composting reactor in order to evaluate the quality of the final compost product. If the test results were not in compliance with the USEPA standards, the model was iteratively modified to fulfill the desired objective. The model was validated using the experimental results. The mixture of Xs:Xa:Xb:Xr with a weight ratio 7.4:1.0:1.4:2.3 allowed optimal moisture content (59.8 ± 0.5%), organic matter (80.0 ± 2.6%), dry matter (40.2 ± 0.6%), C/N ratio (28.0 ± 1.6), and free air space (> 30%) across the composting pile. The final product of compost met the heavy metal and microbial requirements for land application. It can be concluded this mathematical model is a promising method for selecting the optimal amount and type of materials for preparing the initial mixture of co-composting process. Keywords Mathematical model . Co-composting process . Biosolids . Bulking agent . Amendment . Technical scenario . Aerated static pile
Introduction Over the recent years, population growth and urbanization have led to increased wastewater production. In parallel, the
Responsible Editor: Ta Yeong Wu Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-11237-6) contains supplementary material, which is available to authorized users. * Mahdi Farzadkia [email protected]; [email protected] 1
Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
2
Research Center for Environmental Health Technology, Iran University of Medical Sciences, Tehran, Iran
3
Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
more stringent environmental standards and regulations require a higher level of wastewater treatment. Consequently, large amounts of sludge are estimated to produce, consisting mainly of organic materials and dead bacterial cells (Naidoo and Olaniran 2014). Treatment and dispos
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