Seafood-Processing Sludge Composting: Changes to Microbial Communities and Physico-Chemical Parameters of Static Treatment versus for Turning during the Maturation Stage

Abstract

In general, in composting facilities the active, or intensive, stage of the process is done separately from the maturation stage, using a specific technology and time. The pre-composted material to be matured can contain enough biodegradable substrates to cause microbial proliferation, which in turn can cause temperatures to increase. Therefore, not controlling the maturation period during waste management at an industrial level can result in undesired outcomes. The main hypothesis of this study is that controlling the maturation stage through turning provides one with an optimized process when compared to the static approach. The waste used was sludge from a seafood-processing plant, mixed with shredded wood (1:2, v/v). The composting system consists of an intensive stage in a 600L static reactor, followed by maturation in triplicate in 200L boxes for 112 days. Two tests were carried out with the same process in reactor and different treatments in boxes: static maturation and turning during maturation when the temperature went above 55°C. PLFAs, organic matter, pH, electrical conductivity, forms of nitrogen and carbon, hydrolytic enzymes and respiratory activity were periodically measured. Turning significantly increased the duration of the thermophilic phase and consequently increased the organic-matter degradation. PCA differentiated significantly the two treatments in function of tracking parameters, especially pH, total carbon, forms of nitrogen and C/N ratio. So, stability and maturity optimum values for compost were achieved in less time with turnings. Whereas turning resulted in microbial-group stabilization and a low mono/sat ratio, static treatment produced greater variability in microbial groups and a high mono/sat ratio, the presence of more degradable substrates causes changes in microbial communities and their study during maturation gives an approach of the state of organic-matter degradation. Obtaining quality compost and optimizing the composting process requires using turning as a control mechanism during maturation.

Joint Application of Biological Techniques for the Remediation of Waste Contaminated with Hydrocarbons

“…2). Bacteria have been reported to contribute more to the TPH reduction than fungi [32] so, the drop of TPH in this phase can be consequence of bacterial degradation joint to the volatilization of the lightest hydrocarbons as discussed above The fungal diversity index remained at similar values for the first 65 days, coinciding with the thermophilic conditions and in accordance with the observations of Villar et al [23] during the composting of fatty food waste, which indicates the presence of thermotolerant or thermophilic fungi, making it possible to extend the high temperatures by managing the material through turning. As a consequence of the easily assimilable organic compounds being consumed, microbial biomass continued to decrease until it stabilised from the fourth turning, corresponding to the cooling and maturation phase.…”

“…Managing the pile by turning it succeeded in homogenising the material without interrupting the biodegradation process and, consequently, reaching temperatures above 70 °C and prolonging the thermophilic conditions. In addition, the high level of fats from the sludge prolonged the thermophilic temperatures due to the fact that the lipids present provide a greater amount of energy than other organic compounds [23]. The high temperatures (> 70 °C) reached during the process, together with the long duration and stability of the thermophilic stage, caused a significant degradation of organic matter (Table 2), ensuring adequate sanitisation of the material [24].…”

Decentralized Composting of Organic Waste in a European Rural Region: A Case Study in Allariz (Galicia, Spain)

“…During the composting process inside the bioreactor, there were high temperatures reaching 60°C because, as indicated in Ref. [29], the turnings significantly increase the duration of the thermophilic phase and, consequently, a greater degradation of the organic material. The turning of the material caused by the rotation of the drum facilitated the homogenization and the mixing of the material, achieving the elevation of the temperatures until lowering the moisture to values below 30%.…”

Chemical Waste and Allied Products

“…This study also introduces mechanisms underlying the high sorption capacity of hydrochars for both nonpolar and polar OPs. Villar et al, (2016) utilized the waste sludge from a seafoodprocessing plant, mixed with shredded wood (1:2, v/v) as raw materials for composting. This study achieved quality compost and optimized the composting process.…”