Highlighting earthworm contribution in uplifting biochemical response for organic matter decomposition during vermifiltration processing sewage sludge: Insights from proteomics

The vermicomposting for agricultural valorization of sludge from Algerian wastewater treatment plant: impact on growth of snap bean Phaseolus vulgaris L

In the present study, vermicomposting of sewage sludges and their application in agriculture have been investigated. The impact of Eisenia fetida earthworms on the stabilization of these sludges during 7, 14 and 21 days was assessed. The final product was applied as soil amendment (set-1) to evaluate the effects on vegetative parameters (Chlorophyll, carotenoid, number of nodules, leaf weight, and plant height) of Phaseolus vulgaris.L bean. In the second test (set-2), the amendment was made with raw sludge. In the third test (set-3), the worms were added to the raw sludge at the time of spreading and left during the whole period of beans growth. In order to identify and better understand the behavior and role of worms with regard to sludge, their growth (weight and length), some pathogens and physico-chemical parameters were assessed during the vermicomposting. Results showed significant increase of earthworm weight of 10.62, 23.89 and 35.72 % after 7, 14 and 21 days of sludge vermicomposting, respectively, which explain their acclimatization. The vermicomposting caused a decrease of feacal coliforms number and organic matter (OM), an increase in electrical conductivity (EC) and stabilization in pH. Furthermore, significant differences were obtained for all plants vegetative parameters in soil amended with vermicomposts, compared to the control (unamended soil). Indeed, a significant increase of the chlorophyll level (a, b) was noted in the beans having undergone sludge spreading. However, worm-stabilized sludge for 7 days (set-1) showed the highest chlorophyll a and b levels about 16.1 and 24.64 μg/g, respectively, against 10.13 and 4.38 μg/g in the control. For the carotenoid, a significant decrease was observed compared to the control. Our experiments have also showed that the application of vermicomposted sludge significantly increases the number of nodules, leaf weight and plant height of Phaseolus Vulgaris L. snap beans.

Bioelectrochemically-assisted vermibiofilter process enhancing stabilization of sewage sludge with synchronous electricity generation

Bioelectrochemically-assisted vermifilter (VBF_BE) with sewage sludge as the anode fuel was constructed to accelerate composting of sewage sludge, which could increase the quality of the compost and harvest electric energy in comparison with vermicomposting and electrochemical only. Results revealed that the sludge stabilization with a higher soluble chemical oxygen demand (SCOD) and lower NH₄⁺-H during 40 days of composting. At the composting, pH, C/N, electrical conductivity (EC) and germination index (GI) results demonstrated that the maturity degree of VBF_BE4 was higher than that of other VBF_BE. The VBF_BE4 yielded a voltage of 1.024 V and maximum power density of 105.28 mW/m² on 3th day. The bacteria in VBF_BE4 were richer and higher in terms of diversity than those in other VBF_BE, that was demonstrated that combination vermicomposting and electrochemistry could improve the sludge stabilization degree, accelerate sludge composting process and enhance composting maturity.

Study on the biomass and size spectra of bio-particles in vermifilter biofilms

In biological processes of sludge treatment, the sludge yield is closely related to the energy dissipation of entire microbial system. The vermifilter (VF), a novel biofilter, works efficiently due to the introduction of earthworms, which modifies the energy flow pathway through the variations of microbial size structure. For a deep insight into the sludge reduction in the VF, the biomass size spectrum (BSS) was employed to map the energy dissipation in the VF. The results indicated that bio-particles in the size class of [31, 63] μm were reduced most in the excess sludge after the VF treatment. In biofilms, bio-particles in the size class of [31, 63] μm varied most with the filter depth and earthworm density. Eight biomass and size spectra (BSS) were established for all beds of the VF and BF (the control of the VF, without earthworms). The normalized BSS were all linear both in the VF and BF, and their linear regression parameters, the slopes (k) and intercepts (b), varied with the filter depth and the earthworm density. The k and b of the VF were both significantly different from those of the BF. According to the k, the productivity level of largest bio-particles was higher in the VF than in the BF. According to the b, bio-particles at the bottom of size structure could be taken faster in the VF than in the BF. At last, some improvement approaches with some tries were proposed to enhance the sludge treatment capacity of the VF.

Degradation and characteristic changes of organic matter in sewage sludge using Vermi-biofilter system

Vermi-biofilter (VF) System could be an efficient sludge treatment unit in regard of rates and extents of total chemical oxygen demand (TCOD) removal, particularly the first 10 days earthworm-treated. This study characterized the organic matter in sludge before and after VF system treatment, with or without earthworm stage. The 60 days earthworm-treated VF system reached a TCOD removal of 10,450 mg/L, bulk DOC removal of 89.5 mg/L, and earthworm density increase from 32 g/L to 43 g/L in sludge EBOM in 60 days of VF system operation. The aromatic proteins, soluble microbial byproduct-like fluorescent compounds and carboxylic components, aliphatic components (C-H related), hydrocarbon and carbohydrate materials were identified to be principally increased by 10 days earthworm-treated and then degradation in the nest days under VF system.