Profiling of the Microbiome Associated With Nitrogen Removal During Vermifiltration of Wastewater From a Commercial Dairy

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

The review discusses the advancements in vermifiltration research over the last decade, focusing on pollution removal mechanisms, system performance, the fate of filter components, and by-products. Vermifiltration has demonstrated remarkable capabilities, particularly in treating highly contaminated wastewater with Chemical Oxygen Demand (COD) levels exceeding 92,000 mg/L and Biochemical Oxygen Demand (BOD5) levels over 25,000 mg/L, achieving removal rates of approximately 89% and 91%, respectively. Importantly, vermifiltration maintains its effectiveness even with fluctuating organic loads at the inlet, thanks to optimization of parameters like Hydraulic Loading Rate, biodegradable organic strength, earthworm density and active layer depth. Clogging issues can be minimized through parameters optimization. The review also highlights vermifiltrations' potential in co-treating the organic fraction of municipal solid waste while significantly reducing heavy metal concentrations, including Cd, Ni, Pb, Cu, Cr, and Zn, during the treatment process. Earthworms play a pivotal role in the removal of various components, with impressive removal percentages, such as 75% for Total Organic Carbon (TOC), 86% for Total COD, 87% for BOD5, 59% for ammonia nitrogen, and 99.9% for coliforms. Furthermore, vermifiltration-treated effluents can be readily utilized in agriculture, with the added benefit of producing vermicompost, a nutrient-rich biofertilizer. The technology contributes to environmental sustainability, as it helps reduce greenhouse gas emissions (GHG), thanks to earthworm activity creating an aerobic environment, minimizing GHG production compared to other wastewater treatment methods. In terms of pollutant degradation modeling, the Stover-Kincannon model outperforms the first-order and Grau second-order models, with higher regression coefficients (R2 = 0.9961 for COD and R2 = 0.9353 for TN). Overall, vermifiltration emerges as an effective and sustainable wastewater treatment solution, capable of handling challenging wastewater sources, while also producing valuable by-products and minimizing environmental impacts.

Efficacy of a vermifilter at mitigating greenhouse gases and ammonia emissions from dairy wastewater

Dairy effluent is a potential source of gaseous pollutants associated with global warming and soil acidification. Mitigating such emissions during handling and storage requires substantial financial and labor input. This study evaluated a low-cost technology for mitigating gaseous emissions from dairy wastewater. For 9 mo, a pilot-scale vermifilter system installed on a commercial dairy farm was studied. Bimonthly samples of the dairy wastewater influent and effluent from the vermifilter system were collected. These samples' potential gas emissions (ammonia [NH₃ ], methane [CH₄ ], carbon dioxide [CO₂ ], and nitrous oxide [N₂ O]) were measured using a closed-loop dynamic flux chamber method. Results indicated the following reductions in emissions of these gases by the vermifilter system: 84-100% for NH₃ , 58-82% for CO₂ , and 95-100% for CH₄ . Nitrous oxide emissions were mainly below our instrument detection limits and were thus not reported. The vermifilter showed the potential of reducing the global warming potential from the dairy wastewater by up to 100%. This study further indicated that higher ambient temperatures led to higher emissions of CH₄ (R²  = .56) and NH₃ (R²  = .53) from untreated dairy wastewater. Overall, the vermifilter system has potential to mitigate gaseous emissions from dairy wastewater.

Optimization of operational conditions and performances of pilot scale lumbrifiltration for real raw municipal wastewater treatment

Lumbrifiltration (LF) has been promoted as a low-cost, low maintenance and efficient solution for domestic and municipal wastewater treatment especially. However, there have been limited studies investigating the optimal operating conditions and long-term performances of LF systems (especially in temperate climates). The key objectives of this study were to (i) to present an outcome of the operating conditions and associated performance of LF the systems studied in the literature regarding removal efficiencies for nutrients and organic matter (OM) in municipal and domestic wastewater (WW) treatment contexts, (ii) to generate long term and reliable results on the potential performances of LF systems for the treatment of real municipal WW (for both OM and nutrients), (iii) to optimize operational conditions such as active layer height, earthworms density, HLR and earthworms type, conditions for which it is still unclear from the current literature which are optimal, and (iv) to assess the performances of the LF in a "temperate climate" context. Overall, LF systems showed high removal efficiencies for organic matter and nutrients for all the operating conditions tested. The study also confirmed the positive impact of earthworms in achieving high level of nitrification of ammonium after a short start-up period. The system operation and performances were maintained without maintenance for the whole duration of the study (over 250 days), showing the potential for keeping high level of performances for long-term periods. Recommendations are given in relation to LF system design such as optimal active layer height and hydraulic loading rate. The study also demonstrated the applicability and potential of Dendrobaena veneta as an alternative to Eisenia fetida (the latter generally being used in previous studies but are less available in some areas of Europe) for application in municipal wastewater treatment by LF.

Simultaneous Heterotrophic Nitrification and Aerobic Denitrification of Water after Sludge Dewatering in Two Sequential Moving Bed Biofilm Reactors (MBBR)

Water after sludge dewatering, also known as reject water from anaerobic digestion, is recycled back to the main wastewater treatment inlet in the wastewater treatment plant Porsgrunn, Norway, causing periodic process disturbance due to high ammonium of 568 (±76.7) mg/L and total chemical oxygen demand (tCOD) of 2825 (±526) mg/L. The main aim of this study was the simultaneous treatment of reject water ammonium and COD using two pilot-scale sequential moving bed biofilm reactors (MBBR) implemented in the main wastewater treatment stream. The two pilot MBBRs each had a working volume of 67.4 L. The biofilm carriers used had a protected surface area of 650 m²/m³ with a 60% filling ratio. The results indicate that the combined ammonia removal efficiency (ARE) in both reactors was 65.9%, while the nitrite accumulation rate (NAR) and nitrate production rate (NPR) were 80.2 and 19.8%, respectively. Over 28% of the reject water’s tCOD was removed in both reactors. The heterotrophic nitrification and oxygen tolerant aerobic denitrification were the key biological mechanisms found for the ammonium removal in both reactors. The dominant bacterial family in both reactors was Alcaligenaceae, capable of simultaneous heterotrophic nitrification and denitrification. Moreover, microbial families that were found with equal potential for application of simultaneous heterotrophic nitrification and aerobic denitrification including Cloacamonaceae, Alcaligenaceae, Comamonadaceae, Microbacteriaceae, and Anaerolinaceae.