Pilot-scale study of forward osmosis for treating desulfurization wastewater

Mapping the research on desulfurization wastewater: Insights from a bibliometric review (1991-2021)

Desulfurization wastewater in coal-fired power plants (CFPPs) is a great environmental challenge. This study aimed at the current status and future research trends of desulfurization wastewater by bibliometric analysis. The desulfurization wastewater featured with high sulfate (8000 mg/L), chlorite (8505 mg/L), magnesium (2882 mg/L) and calcium (969 mg/L) but low sodium (801.82 mg/L), and the concentrations of the main contaminants were critically summarized. There was an increasing trend in the annual publications of desulfurization wastewater in the period from 1991 to 2021, with an average growth rate of 15%. Water Science and Technology, Desalination and Water Treatment, Energy & Fuels, Chemosphere, and Journal of Hazardous Materials are the top 5 journals in this field. China was the most productive country (58.3% of global output) and the core country in the international cooperation network. Wordcloud analysis and keyword topic trend demonstrated that removal/treatment of pollutants dominated the global research in the field of desulfurization wastewater. The primary technologies for desulfurization wastewater treatment were systematically evaluated. The physicochemical treatment technologies occupied half of the total treatment methods, while membrane-based integrated processes showed potential applications for beneficial reuse. The challenges and outlook on desulfurization wastewater treatment for achieving zero liquid discharge are summarized.

A Comprehensive Review on Forward Osmosis Water Treatment: Recent Advances and Prospects of Membranes and Draw Solutes

Forward osmosis (FO) is an evolving membrane separation technology for water treatment and reclamation. However, FO water treatment technology is limited by factors such as concentration polarization, membrane fouling, and reverse solute flux. Therefore, it is of a great importance to prepare an efficient high-density porous membrane and to select an appropriate draw solute to reduce concentration polarization, membrane fouling, and reverse solute flux. This review aims to present a thorough evaluation of the advancement of different draw solutes and membranes with their effects on FO performance. NaCl is still widely used in a large number of studies, and several general draw solutes, such as organic-based and inorganic-based, are selected based on their osmotic pressure and water solubility. The selection criteria for reusable solutes, such as heat-recovered gaseous draw, magnetic field-recovered MNPs, and electrically or thermally-responsive hydrogel are primarily based on their industrial efficiency and energy requirements. CA membranes are resistant to chlorine degradation and are hydrophilic, while TFC/TFN exhibit a high inhibition of bio-adhesion and hydrolysis. AQPs are emerging membranes, due to proteins with complete retention capacity. Moreover, the development of the hybrid system combining FO with other energy or water treatment technologies is crucial to the sustainability of FO.

The noteworthy chloride ions in reclaimed water: Harmful effects, concentration levels and control strategies

Chloride ions (Cl^-), which are omnipresent in reclaimed water, can cause various problems in water reuse systems, especially during water transmission and at end use sites. Although reverse osmosis (RO) is considered as an effective technology to reduce chloride, its high investment and complex maintenance requirements hinder its application in many water reclamation plants (WRPs). Recently, several technologies bringing new options to better deal with chloride have gained increased attention. This review provides detailed information on the harmful effects, concentration levels, and sources of chloride in reclaimed water and summarizes and discusses various chloride removal technologies, including non-selective methods (e.g., membrane filtration, adsorption and ion exchange, oxidation, and electrochemical methods) and selective methods (e.g. precipitation and specially designed electrochemical methods). Among these, Friedel's salt precipitation and capacitive deionization showed attractive development potential. This review also proposes a holistic framework for chloride control from aspects of "Fit-for-Purpose" planning, technical system development, and whole process optimization, which could facilitate the planning and operation of long-term sustainable water reuse practices.