Design, performance evaluation and investigation of the dynamic mechanisms of earthworm-microorganisms interactions for wastewater treatment through vermifiltration technology

Abstract

The present study points to the relevance of the earthworms-microorganism"s symbiotic and synergistic interactions that drive the wastewater treatment by identifying the most essential mechanisms underlying the removal of contaminants during vermifiltration technology. Previous studies have showed the presence of earthworms improves treatment performance of vermifilter (VF), but earthworm microbial community dynamics, their structure and functional characteristics in VF were not fully investigated. To investigate the effects of earthworms on the inherent microbial community of the VF, the present study envisages the dynamics of the complex symbiosis of earthworms & microorganisms associated to the treatment mechanisms. In this study, the design, operations and performance evaluation and influent, effluent and filter media layer were investigated for microbial diversity inside the earthworm population, along with the antimicrobial activity, enzymatic activity, and protein profiling assays. The results showed that earthworm gut microbial communities were dominated by Gammaproteobacteria, and the percentages arrived to 59-60% of the microbial species detected, while filter media layer showed presence of Firmicutes and Actinobacteria. The protein profiling of the microbiota associated with the VF showed that earthworms feeding and earthworm-microorganism . CC-BY-NC 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made interaction were responsible for enhanced treatment performance. The finding provides an insight into the complex earthworm microbial dynamics and mechanisms for wastewater treatment in VF. Furthermore, earthworm predation strongly regulated microbial biomass while improving microbial activity, and is deciphered as the possible mechanisms behind the vermifiltration technology.

Effects of bed depths and the ratio of aerobic to anaerobic zone on the performance of horizontal subsurface flow macrophyte‐assisted high‐rate vermifilters treating synthetic brewery wastewater

“…This could be due to the intensified burrowing activities of the EWs at lesser submerged bed depth, which intensified the natural air circulation inside the HSSF‐MAVF (Dey Chowdhury & Bhunia, 2021). EWs cannot survive under water‐logged conditions, and thus, with the increase in submerged bed depth, the activities of the EWs deteriorated, increasing the anaerobicity inside the system (Figure 3) and causing an overall reduction in the COD removal efficiency (Arora et al, 2020; Sinha et al, 2008). Apart from the enhanced aerobic biodegradation of organics, the adsorption and filtration of organics by the bed materials were also increased with the decrease in the submerged bed depth for a specific total vermibed depth, causing a higher COD removal efficiency.…”

“…Earlier, the presence of Aeromonas hydrophila in the gut and casting of EWs was reported by Furlong et al (2002), which is an enzyme‐producing bacteria, ensuring enhanced biodegradation of organics. Again, Arora et al (2020) found the dominance of Gammaproteobacteria (up to 60% of the microbial community) in EWs' bodies, whereas the VF was governed by Firmicutes (responsible for degrading complex carbohydrates) and Actinobacteria (biofactory of enzymes; produces substrate‐specific enzymes even in the extreme adversities). Moreover, the predominance of cellulase, amylase, and protease was also noticed.…”

“…However, the potential of the vermifiltration/macrophyte‐assisted vermifiltration technology in removing nutrients, especially N, from wastewater has not been fully identified, which warrants intensive research. For example, Arora et al (2020) reported that the vermifiltration of institutional wastewater resulted in a hike in the effluent nitrate nitrogen (NO 3 − –N) concentration compared to its influent concentration. This could be due to the provision of insufficient HRT of wastewater inside the VF or the unavailability of anoxic/anaerobic pockets inside the vermibed, which restricted the denitrification process (Bandyopadhyay et al, 2023; Dey Chowdhury et al, 2022; Dey Chowdhury & Bhunia, 2021; Jiang et al, 2016).…”

Microplastics in agroecosystems: A review of effects on soil biota and key soil functions

“…and biodegradable materials, added at 1% (w/w), caused an increase in soil pH after 2 months of exposure compared with the control treatment, while after 4 months of exposure, soil pH was decreasing again (Qi et al, 2019) (Arora et al, 2020;Zhong et al, 2021).…”

New developments on vermifiltration as a bio-ecological wastewater treatment technology: Mechanism, application, performance, modelling, optimization, and sustainability

“…In that synergy, the microorganisms biochemically degrade the matter while the earthworms by muscular actions also allow a degradation but especially a homogenization of the matter. Through the investigation of bacterial and protein characteristics, it has been demonstrated by Arora et al [ 22 ] that the feeding of earthworms and the interactions between earthworms and micro-organisms are responsible for the removal of pollutants during the vermifiltration process. Indeed, the digestion of organic matter (OM) in the digestive tract of earthworms is carried out within the framework of a mutualism existing between the earthworm and the microorganisms ingested in the environment.…”