Photocatalytic degradation of Rhodamine‐B dye using composite prepared from drinking water treatment sludge and nano TiO 2

Persulfate catalyst synthesized with waterworks sludge for degrading Safranine T in the presence of boron

Energy conservation and emission reduction are the general trend of the present world. In this study, a catalyst of 3WSH based on the waste recycle of waterworks sludge (WS) and Chinese herbs was prepared using one-step calcination treatment and then characterized by SEM, XRD, XPS, FTIR and BET. The catalytic performance of 3WSHB for activating potassium persulfate (PDS) was evaluated through the degradation of Safranine T (ST) in the presence of boron powder (B). The effects of vital parameters on ST removal were systematically studied, including PDS concentration, 3WSHB dosage, initial solution pH, B dosage, temperature and coexisting cations. The highest efficiency of ST removal was up to 93.0% under the optimal condition with 1.85 mM of PDS, 0.3 g/L of 3WSHB, 0.35g/L of B, 7 of pH. EPR and free radical quenching experiments demonstrated that •OH was the dominant reactive oxygen species for ST degradation in the PDS/3WSHB/B system. Moreover, the intermediates determined by HPLC-MS indicated that the oxidization of benzene ring substituents in ST and a hydrogen abstraction by electron transfer might occur during ST degradation. The dissatisfied reuse performance of 3WSHB might be attributed to its low Fe content and simple reusing way. The results demonstrate the effectiveness of WS recycling and reuse in the field of pollutant remediation.

Application of modified water treatment residuals in water and wastewater treatment: A review

Large quantities of sludge known as water treatment residuals (WTRs) are generated from water treatment facilities across the world. Various attempts have been made to reuse these residuals. Among the different applications of WTRs, their reuse in water and wastewater treatment has received more attention. However, direct application of raw WTRs is associated with some limitations. In the last decade, in order to improve their characteristics, numerous investigators have modified WTRs by different methods. This paper reviews the different methods applied to WTRs to enhance their characteristics. The effects of these modifications on their characteristics are explained. The applications of modified WTRs as a filtration/adsorption medium for treating textile/dye wastewater, groundwater containing different anionic and cationic pollutants, storm water runoff, and as a substrate in constructed wetlands are presented in detail. Future research needs are highlighted. The review clearly indicates the potential of different modification methods to improve the removal of a variety of pollutants by WTRs from water and wastewater.

Co-pyrolysis technology for enhancing the functionality of sewage sludge biochar and immobilizing heavy metals

Sewage sludge (SS) is a frequent and challenging issue for countries with big populations, due to its massive output, significant hazard potential, and challenging resource utilization. Pyrolysis can simultaneously realize the reduction, harmlessness and recycling of SS. Co-pyrolysis offers a wide range of potential in terms of increasing product quality and immobilizing heavy metals (HMs), thanks to its capacity to use additives to address the mismatch between SS characteristics and pyrolysis. High-value utilization potential of SS biochar is the key to evaluating the advancement of treatment technology. A further requirement for using biochar resources is the immobilization and bioavailability reduction of HMs. Due to the catalytic and synergistic effects in the co-pyrolysis process, co-pyrolysis SS biochar exhibits enhanced functionality and has been applied in soil improvement, pollutant adsorption and catalytic reactions. This review focuses on the research progress of different additives in improving the functionality of biochar and influencing the behavior of HMs. The key limitation and challenges in SS co-pyrolysis are then discussed. Future research prospects are detailed from seven perspectives, including pyrolysis process optimization, co-pyrolysis additive selection, catalytic mechanism research of process and product, biochar performance improvement and application field expansion, cooperative immobilization of HMs, and life cycle assessment. This review will offer recommendations and direction for future research paths, while also assist pertinent researchers in swiftly understanding the current state of SS pyrolysis research field.

Ecologically Engineered Systems for Treating Agriculture Runoff by Integrating “Wastes” into Constructed Wetlands

Runoff from agricultural irrigation is contaminated and loaded with pesticides. Frequent toxic levels of pesticide detection in the ecosystem motivate scientists and engineers to diminish agro-chemicals flowing into the environment. Constructed wetland, CWs, treatments are a sustainable methodology of special interest since it possess a symbiosis value. Flytek (FT) pesticide use has increased at an unprecedented rate for crop production as well as an increase in runoff loaded with Flytek. This study introduces the use of constructed wetlands based on an alum- sludge substrate for the purpose of Flytek (FT) removal performance. The system is based on an adsorption column and a sludge cake coupled with gravel acting as a carrier in order to be an adsorption bed and filtration system for Flytek removal. The structure, morphology and characteristics of the adsorption bed material “alum sludge” were characterized using X-ray diffraction spectroscopy and Scanning Electron Microscope (SEM). Additionally, Fourier-Transform infrared spectroscopy (FTIR) was explored. The experimental results revealed that a vertical flow constructed wetland is significant in eliminating the Flytek pesticide. However, the amount and height of sludge in a wetlands column affects its removal efficiency with the optimal removal (96%) being linked to the presence of sludge in 80%. Moreover, temperature, pH and the FT load showed a significant effect in removals, with the optimal operating conditions being recorded at 7.2 pH, 26 °C and 100 ppm of FT. The kinetic modeling is also investigated to validate the practical life applications and designs, and the results verified the reaction follows the pseudo 2nd-order reaction kinetic model according to the correlation coefficient factor. Furthermore, according to the isotherm model results the scheme follows the Freundlich isotherm model. Such preliminarily data of a gravel-alum-sludge-adsorption-column scheme is a good indicator in developing a constructed wetland facility being a good candidate for controlling agriculture effluent streams.