Biofiltration is a process in which an otherwise conventional granular filter is designed to remove not only fine particulates but also dissolved organic compounds through microbial degradation. Biofiltration can reduce the need for chemicals in drinking water treatment and thus improved applications of biofiltration in drinking water treatment can be viewed as green or sustainable engineering technology. Recent trends in biofiltration technology for drinking water treatment have or have attempted to extend the performance of biofilters through gaining a better understanding of operational constraints. This review articles summarizes important operational parameters influencing biofiltration performance such as hydraulic loading, empty bed contact time (EBCT), temperature, media type, and backwashing conditions. In addition, recent advancements in biofiltration operations including, ozonation, ammonia removal and the influence of nutrient (nitrogen, phosphorous) supplementation to facilitate carbon removal are explored.

No abstract

Diarrheal illnesses claim the lives of hundreds of thousands of children each year, most of whom live in rural and low-income communities. Ceramic Water Filters (CWF) are widely regarded as one water treatment technology with the potential to increase access to safe drinking water. While physical filtration mechanisms are a key contributor to improving the water safety, silver is commonly added to improve disinfection performance. Therefore, a thorough review of silver disinfection efficacy and disinfection mechanisms in relation to CWFs are critically important. This paper reviews filter mechanisms and efficacy for bacteria removal for cases with and without silver addition. Method of silver application (dipping, painting, or co-firing) is assessed. Silver release and retention is discussed. The findings from this paper illustrate that eluted silver contributes to filter bacterial disinfection. However, more research is needed on the impact of silver on preventing a "slime layer" on the filter surface and receptacle. Silver application method, water quality and particle characteristics were demonstrated to impact release. For instance, co-firing results in the most consistent elution over time but at lower concentrations than other methods. Finally, research into alternative metals to silver for enhanced disinfection present emerging opportunities within the CWF field.

No abstract

Catalyzed hydrothermal carbonization (CHTC) was used to produce hydrochar biofuel from wood chips at 240 °C in 1 h batches that included recycling of the process liquid. Infrared spectra showed changes in the chemical structure consistent with dehydration and decarboxylation. The CHTC hydrochar had higher heating values (HHV) of 28.3 MJ/kg, energy yield of 64%, and hydrogen-to-carbon (H/C) and oxygen-to-carbon (O/C) ratios similar to those of coal. The same process without the catalyst (HTC) produced a hydrochar with HHV of 27 MJ/kg, energy yield of 57%, and H/C and O/C ratios similar to those of lignite. Partial recycling of the CHTC process liquid resulted in a 5% increase in the energy yield; elemental composition, HHV, and scanning electron microscopic images of the CHTC hydrochar for different recycles were indistinguishable. Densified CHTC hydrochar pellets were 97% durable and hydrophobic when compared with wood pellets and torrefied-wood pellets, which was shown by water ingress measurements using an electrochemical cell with pellet electrodes. The CHTC process with recycling has the potential to provide a green hydrochar biofuel with excellent handling, storage, and transportation properties, that could be a suitable direct replacement for coal.