Tunisia achieved a relatively satisfactory wastewater collection and treatment rate of 86% in 2019 compared to its fellow countries, remarkably more threatened by water scarcity and waste management problems. However, the environmental effect of wastewater treatment in Tunisia still needs to be clarified. In this study, a life cycle assessment of WWTPs in Tunisia was performed to analyze the impact of a WWTP under current conditions. Then different scenarios with biogas production were compared to the baseline scenario to conclude the least damaging to the environment. Results showed that wastewater treatment and sludge landfilling were the processes with the highest impact on all the damage categories, especially on human health (41.8% and 41.9%). Comparing the baseline scenario to alternative scenarios with biogas production showed that sludge drying, and biogas production reduced the WWTP’s impact, especially when sludge was mixed with municipal solid waste by −30.41%. Such results provide insight for decision-making on the improvement options for the wastewater treatment sector by considering emissions through policy revision and strategy design, which will contribute to sustainable biogas production.

This study investigated the long-term performance of iron-added sediment microbial fuel cells (SMFCs) in suppressing phosphorus (P) release from agricultural drainage sediments. Sediment samples were collected from two drainage canals in livestock farming (LS) and pasture-grown (PS) areas in Kasaoka, Japan. Iron-added sediments were prepared by mixing FeCl₃·6H₂O at 0.05% (wt/wt). A graphite-felt anode and a carbon rod cathode were used in a dual-chamber SMFC (height: 146 mm, diameter: 45 mm), which was operated under open (OC) or closed circuit (CC) conditions at 25°C. The experiments consisted of 8 treatments in triplicate: LS and PS sediments × Fe or no-Fe × OC or CC. Phosphorus release from LS sediment was higher than from PS with a lower total P content. Under the SMFC operation, P release was reduced until day 42. Afterward, P concentrations became similar between OC and CC conditions, and iron addition increased P release from sediment, probably because of P mineralization. Our study suggested that SMFCs effectively reduced P through Fe precipitation until day 42, when the resistor was reduced. However, SMFC operation or iron addition would increase organic matter decomposition in sediment, which in turn enhanced P release from sediment.

Invasive alien species Alternanthera philoxeroides was found on Lake Biwa shore for almost two decades and has been causing huge loss for this region. This study aims at investigating three impact factors on reproduction of A. philoxeroides, namely nutrients, stem length, and stem diameter. Utilizing a ternary configuration dispersion method on 120 fragment samples collected from Lake Biwa shore after 10-days cultivation, the result indicates that nutrient salts significantly enhance growth (p < 0.01, Welch’s t-test), highlighting the species’ preference for eutrophic environments. Smaller stem fragments exhibit reduced growth, emphasizing the importance of thorough removal to minimize its persistence. Comparative analysis with Ludwigia grandiflora underscores that the latter exhibited bigger leaves under same experiment condition, and stem diameter significantly influence on its growth (37.7% contribution rate). These findings not only offer valuable references for elimination activities, but also stress the need for appropriate eradication strategies to preserve Lake Biwa’s aquatic ecosystem, contributing valuable insights to invasive species management in ecologically sensitive areas.

UV-LEDs are a promising technology to degrade pharmaceuticals in water. However, to consider the installation of a UV-LED system to actual treatment systems, the degradation by-products of pharmaceuticals, their toxicities, and their degradation pathways should be better understood to determine optimal UV irradiation conditions. In addition, it is necessary to estimate the impact of co-existing substances such as nitrate ion (NO₃⁻) and dissolved organic matter (DOM). We analyzed degradation by-products of five common pharmaceuticals by high resolution mass spectrometry, and ion chromatography to understand the decomposition mechanisms of pharmaceuticals in Milli-Q water and evaluated the influence of NO₃⁻ and DOM in environmental water in UV-LED degradation experiments. The results showed that pharmaceutical degradation percentage was nearly 100% for most of the target compounds (except ibuprofen) in Milli-Q water. Additionally, a part of the degradation mechanism of sulfamethoxazole was clarified. It is suggested that UV absorption occurred at the benzene ring and transfer energy resulted in S-N bond cleavage via homolysis. UV irradiation in the presence of DOM or NO₃⁻ promoted the dichlorination reaction by the photosensitizing effect of chlorinated organic compounds such as diclofenac and triclosan, suggesting that 280 nm irradiation is effective for the degradation of pharmaceuticals in water treatment.