Activated sludge models have assumed that a portion of organic solids in municipal wastewater influent is unbiodegradable. Also, it is assumed that solids from biomass decay cannot be degraded further. The paper evaluates these assumptions based on data from systems operating at higher than typical sludge retention times (SRTs), including membrane bioreactor systems with total solids retention (no intentional sludge wastage). Data from over 30 references and with SRTs of up to 400 d were analysed. A modified model that considers the possible degradation of the two components is proposed. First order degradation rates of approximately 0.007 d(-1) for both components appear to improve sludge production estimates. Factors possibly influencing these degradation rates such as wastewater characteristics and bioavailability are discussed.
Although the paper industry processes polymeric materials and discharges large amounts of wastewater, no research on microplastics in the wastewater from paper mills has been published to date. This study is the first to investigate this issue. The wastewater treatment plants of twelve representatively selected German paper mills were investigated using an analysis protocol based on µ-Raman spectroscopy.
Nitrogen emissions up to the standard are a major challenge for wastewater treatment plants in alpine and high-altitude areas. The dosing of carriers can improve the nitrogen removal efficiency of the system at low temperatures; however, the mechanism of action of sludge and biofilm in nitrogen removal remains unclear. This study elucidated the internal mechanism of nitrogen removal via the function of microbial metabolism in sludge and biofilm at low temperatures.
In subsurface water, humic acid (HA) can react with active chlorine to form carcinogenic compounds, posing ecological issues and health risks. This study aims to create sludge activated carbon (SAC), combine it with Fe, and activate peroxosulfate (PMS) to remove HA from water. To verify the successful modification of SAC, the physicochemical properties were characterized using various methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer Emmett Teller (BET) analysis, and X-ray photoelectron spectroscopy (XPS).
Urea is a major issue in human wastewater because it may be easily broken down by the urease enzyme produced by bacteria, leading to ammonia production. Due to its ability to increase soil pH and eutrophicate streams, ammonia-containing effluent emissions pose environmental and health risks. This study aimed to evaluate the effectiveness of various treatment approaches in reducing urea concentrations by comparing the removal rates of conducting electrocoagulation (EC), EC followed by chemical coagulation (EC-CC), and CC followed by electrocoagulation (EC-CC).
Efforts addressing sludge management, food security, and resource recovery have led to novel approaches in these areas. Electrically assisted conversion of sludge stands out as a promising technology for sewage sludge valorization, producing nitrogen and phosphorus-based fertilizers. The adoption of this technology, which could lead to a fertilizer circular economy, holds the potential to catalyze a transformative change in wastewater treatment facilities toward process intensification, innovation, and sustainability.
