Synthesis of high quality boehmite and γ-alumina for phosphorus removal from water works sludge by extraction and hydrothermal treatment

Transforming drinking water treatment residuals into efficient adsorbents: A review of activation and modification methods

The management of drinking water treatment residuals (DWTRs) poses significant environmental and economic challenges for water treatment facilities; however, these residues have considerable potential as effective adsorbents for pollutant removal. The objectives of this review are to evaluate research conducted from 2015 to 2024 on treatment and modification techniques aimed at enhancing DWTRs' efficacy as adsorbents, analyze the influence of preparation methods on DWTRs performance, evaluate DWTRs adsorbents for different pollutants, and discuss the limitations and challenges in DWTRs applications. The review addresses the knowledge gap by detailed analysis of these advanced modification methods, which have not been extensively reviewed before, and their direct impact on the physicochemical properties and adsorption performance of DWTRs. The review explores various methods including thermal treatment, chemical activation, granulation, pelletization, and the development of composite materials. Key findings indicate that thermal treatment significantly increases surface area and porosity, while chemical activation introduces functional groups that enhance adsorption capacity. Composite DWTRs, incorporating metals, organic compounds, or magnetic properties, demonstrate superior performance in adsorbing diverse contaminants such as dyes and heavy metals. Despite these advancements, challenges remain, particularly in reporting the life cycles and costs of the treated and modified DWTRs and the regeneration of spent adsorbents. The review highlights the importance of optimizing preparation techniques to enhance the physicochemical properties and adsorption performance of DWTRs. By synthesizing existing knowledge and identifying key areas for future research, this review aims to advance sustainable practices in water treatment and resource recovery, aligning with global sustainability goals.

A novel modified nano-alumina composite sol for potential application in forest firefighting

Herein, modified ammonium polyphosphate wrapped nano-alumina (mAPP@Als) was first synthesized and then dispersed in traditional fire extinguishing solution (FES) to fabricate a FES-mAPP@Als composite sol. It was found that the phosphorus-silica containing units were attached onto the nano-alumina surface, and the mAPP@Als particles showed excellent dispersion level in FES with a single-domain particle size distribution range. Due to the synergistic effects of the phosphorus-nitrogen and silica-alumina flame retardant components, FES-mAPP@Als (5% concentration) coated wood exhibited improved limiting oxygen index (33.2%) and carbonization ability, and depressed heat release (41.9%) and smoke production (10.7%), as compared to the pristine wood. In addition, the FES-mAPP@Als composite sol showed enhanced fire-extinguishing and anti-reignition capacities compared to the FES. This research offers a novel composite sol fire extinguishing agent for fighting forest fires.

Phosphorus adsorption and organic release from dried and thermally treated water treatment sludge

The study investigated water treatment sludge (WTS) as a phosphorus (P) adsorbent and examined the release of organic matter during the P adsorption process. Previous studies indicated that WTS is an effective adsorbent for P but also releases organic matter, which may affect the organoleptic properties of treated water, but no study has characterised organic release and conducted an in-depth study on its behaviours. This study characterised the organic release during the P adsorption process from four different WTS samples. This study also offers results from a 60-day column experiment that indicate that WTS columns effectively removed the majority of P from the 2 mg/L feed solution. The total organic carbon (TOC) release was gradually reduced from 24.9 mg/L on day 1 to stable levels of 4.4 mg/L to 4.1 mg/L from day 22 onwards. After 60 days, when the organic matter was nearly exhausted, WTS columns were still effective in P adsorption from the solution. In addition, the thermal treatment of WTS at different temperatures was investigated to reduce TOC release and increase P adsorption. The results showed that thermal treatment not only minimized TOC release but also enhanced the P adsorption capacity of the sludge. In a 24-h batch experiment, WTS treated at 600 °C showed the highest P adsorption (1.7 mg/g) with negligible TOC release when compared to sludge treated at 500 °C WTS (1.2 mg/g), 700 °C WTS (1.5 mg/g) and dried WTS (0.75 mg/g). However, the release of inorganic compounds slightly increased after thermal treatment. Future studies could focus on determining whether the thermal processing of WTS which can enhance the WTS's adsorption to emerging pollutants like per- and poly-fluoroalkyl substances and other contaminants. The findings of this study could influence the management practices of water authorities and contribute to the water sector's sustainability objectives.

Sewage phosphorus recovery through sachets loaded with water treatment plant sludge

Conventional wastewater treatment plants (WWTPs) present low phosphorus (P) removal capacity. Conversely, water treatment plants (WTPs) produce sludge with great P sorption from wastewater; however, directly adding the sludge into the wastewater treatment system could increase the effluent turbidity. As a novel approach, the present study evaluated the performance of WTP sludge within paper sachets for P removal from treated sewage. Different sludge concentrations (2-30 g L-1) and contact times (1-27 d) were applied to treat sewage from a university WWTP outlet. The sludge was characterized by P, Fe, and Al content. Larger sludge masses showed higher P removal efficiencies due to their high Fe content, especially at longer contact times (up to 100% at the final of the experiment). However, there is a more significant P reduction in the first 10 d (more than 90% in the most efficient treatment - 30 mg L-1). Based on the kinetic and isotherm analyses and the sludge chemical composition, precipitation proved to be a mechanism of great importance in P removal. Therefore, WTP sludge sachets can be a promising way to remove P from sewage, and the formed solid waste might be reused as an alternative fertilizer.