Review of Co-Composting Municipal Sewage Sludge with a Variety of Biological Waste

Abstract

Background & objective: Direct application of sewage sludge in agriculture has been limited due to the presence of pathogens, inappropriate fermentation of organic waste and the presence of heavy metals. Co-composting of sewage sludge with biological waste is a method to reuse waste that leads safe disposal of sludge and waste. The purpose of this study was to review the advantages of co-compost and the possibility of compost production from a mixture of sewage sludge and biological waste. Method: In this paper, various methods for the production of co-compost were also reviewed. In this paper several factors including composting process optimization, compost controlling agents, co-composting raw materials and use of sewage sludge and biological wastewater, in the preparation of compost were evaluated as well as the role of co-compost in the challenge of agricultural wastewaters. Results: The raw sludge in a compost with organic waste, along with biochemical solids (fat, protein, and cellulose), are pure in terms of process evolution, the destruction of biochemical compounds in composting materials, the potential for pathogen inactivation, nutrient retention and improved biological activity. Proper management of municipal sewage treatment, organic and biological waste produced in the agro-industry play an important role in promoting the community health and the environment. The high cost of biological waste disposal, its environmental impacts, and the many risks associated with the use of chemical fertilizers are the problems due to ignorance compost production. Conclusion: Therefore, producing compost and co-comosting should be considered to promot environmental health.

Changes in microbial populations during co-composting of dewatered sewage sludge with pruning wastes in windrow piles

“…The pH values in the early stages of the process were 7.7 and 7.5 for TW2 and TW3 piles, respectively. Degradation of OM and accumulation of organic acids can decline pH at the beginning of the process (Zazouli and Ala 2019). Generally, the values of pH for both piles after the 2 nd week gradually increased to a rate of 8.5 in the 5 th week.…”

“…As indicated in Table 1, in the early stages, the number of fecal streptococci increased to 7 logs MPN/g DW and 7.9 logs MPN/g DW in TW2 and TW3, respectively and after that, these bacteria decreased in both piles. (Zazouli 2019) and (Nafez et al 2013) reported that the total coliforms have lower values in returned piles in the stability phase. Also in (Ma et al 2019) study, the number of fecal coliforms and Streptococci in compost piles decreased from log 5 and log 2.49 to log 2.27 and log 2.12, respectively.…”

“…There are numerous methods for SS composting. Zazouli and Ala reported that increasing the volumetric ratio of the bulking agent to SS, in an aerated static pile composting process, improved the temperature rising rate and shortened the composting period (Zazouli and Ala 2019). The effectiveness of the composting process is directly associated with the structure of microbial communities in turned windrows and aerated static piles, which can be influenced by temperature, pH, moisture content, and C: N ratio (Nafez et al 2015a).…”