Impact of ozonation and biologically enhanced activated carbon filtration on the composition of micropollutants in drinking water

Abstract

A pilot-scale drinking water treatment process for Songhua River, including conventional treatment (coagulation-settlement and rapid sand filtration), ozonation, biological enhanced activated carbon (BEAC) filtration, and chlorination disinfection, was carried out in this study. To investigate the impact of ozonation and BEAC filtration on removing the composition of micropollutants in drinking water, we detected the micropollutant composition from each stage of the treatment process by non-targeted analysis using a GC-MS technique and compared the results between effluents of single BEAC and O-BEAC processes. Aromatic compounds and esters could be abated efficiently during single BEAC filtration via biodegradation and adsorption; however, possible metabolic products (i.e., alkenes) were formed by biodegradation. Comparatively, O-BEAC process could reduce micropollutants much more significantly than single BEAC process especially for aromatic compounds including substituted benzenes and polycyclic aromatic hydrocarbons (PAHs) without the formation of metabolic products through the coupling effect of oxidation, biodegradation, and adsorption, suggesting that ozonation improved the removal potential of micropollutants in the BEAC process. In addition, conventional and novel chlorinated disinfection by-products were also measured during post-chlorination.

New directions and challenges in engineering biologically-enhanced biochar for biological water treatment

“…The effects of other upstream treatments such as coagulation, ozonation or chlorination on bacterial growth and density have to be considered, as these treatments can impact biofilm development. For example, residual chlorine in the influent water to a pilot-scale BAC unit reduced the bacterial attachment on its surface, while a pre-ozonation process before BAC treatment improved the biological activity of the biofilm for contaminant degradation in many cases 18,23,[106][107][108] . These aspects should be considered during design of BEB filters for industrial/ municipal applications.…”

“…When exhausted filters are used, large amounts of organic matter and nutrients such as ammonia and phosphorus in the effluent water can lead to biofilm formation in the distribution networks 18,26 . It is thus important to adjust the process parameters, frequency and intervals of backwashing and regeneration/change to fresh BEB filters 106 The presence of toxic and carcinogenic compounds such as Polycyclic Aromatic Hydrocarbons (PAH) and Volatile Organic Compounds (VOCs) that form during pyrolysis and deposit on biochar surface/pores is undesirable 108 . However, production of clean biochar is feasible and can be achieved by tuning a few key process parameters such as peak temperature, feedstock type, residence time and carrier gas flow rate [111][112][113] .…”