Investigation of biotransformation, sorption, and desorption of multiple chemical contaminants in pilot-scale drinking water biofilters

Abstract

The evolving demands of drinking water treatment necessitate processes capable of removing a diverse suite of contaminants. Biofiltration can employ biotransformation and sorption to remove various classes of chemicals from water. Here, pilot-scale virgin anthracite-sand and previously used biological activated carbon (BAC)-sand dual media filters were operated for ∼250 days to assess removals of 0.4 mg/L ammonia as nitrogen, 50-140 μg/L manganese, and ∼100 ng/L each of trace organic compounds (TOrCs) spiked into pre-ozonated Colorado River water. Anthracite achieved complete nitrification within 200 days and started removing ibuprofen at 85 days. Limited manganese (10%) removal occurred. In contrast, BAC completely nitrified ammonia within 113 days, removed all manganese at 43 days, and exhibited steady state removal of most TOrCs by 140 days. However, during the first 140 days, removal of caffeine, DEET, gemfibrozil, naproxen, and trimethoprim decreased, suggesting a shift from sorption to biotransformation. Acetaminophen and sulfamethoxazole were removed at consistent levels, with complete removal of acetaminophen achieved throughout the study; ibuprofen removal increased with time. When subjected to elevated (1 μg/L) concentrations of TOrCs, BAC removed larger masses of chemicals; with a subsequent decrease and ultimate cease in the TOrCs spike, caffeine, DEET, gemfibrozil, and trimethoprim notably desorbed. By the end of operation, anthracite and BAC exhibited equivalent quantities of biomass measured as adenosine triphosphate, but BAC harbored greater microbial diversity (examined with 16S rRNA sequencing). Improved insight was gained regarding concurrent biotransformation, sorption, and desorption of multiple organic and inorganic contaminants in pilot-scale drinking water biofilters.

Deep-bed filters as post-treatment for ozonation in tertiary municipal wastewater treatment: impact of design and operation on treatment goals

“…In accordance with these results, other studies also observed better removal of biodegradable organic matter on BAC than on non-adsorptive filter materials. [34][35][36] Multiple explanations for the benefits of BAC have been reported. The porous structure of GAC media provides a significantly higher specific surface area and increased roughness of the surface, compared with compact grains of anthracite or sand.…”

Persistent contaminants of emerging concern in ozone‐biofiltration systems: Analysis from multiple studies

“…The majority of the studies evaluated used GAC as the biological filtration media, although a number of facilities also used other media such as sand and anthracite. Previous studies have shown that vastly different microbial populations were developed in different media, with carbon‐based media exhibiting greater microbial diversity, potentially impacting BAF performance (Gerrity et al, 2018; Greenstein, Lew, Dickenson, & Wert, 2018; Vignola, Werner, Wade, Meynet, & Davenport, 2018). The impact of media type on CEC removal in this study was assessed through comparison of selected CEC along the treatment train of two full‐scale facilities using different media type but similar O 3 :TOC ratio (0.5–0.65 mg O 3 /mg TOC): project J used anthracite in their BAF system, while project K used GAC.…”

“…It is also important to note that, in addition to the factors mentioned above, BAF performance is also influenced by media age and backwashing frequency (Arnold et al, 2018; Sundaram et al, 2020), as well as acclimation periods (Greenstein et al, 2018, p. 47; Zearley, 2012, p. 170). The effect of media age is especially important when using GAC as the contaminant removal will transition from carbon‐based to mixed carbon to noncarbon‐based (e.g., biodegradation, adsorption to biofilms) and finally to full biodegradation at approximately 20,000 bed volumes (BVs) based on a study conducted by Sundaram et al (2020).…”

Implementing Ozone‐BAC‐GAC in potable reuse for removal of emerging contaminants

“…Desorption of a compound indicates that it was previously removed by adsorption and not biodegradation. Sundaram and Pagilla (2019) showed that more than 90% of sucralose was removed by adsorption onto GAC media, while Greenstein et al (2018) did not report removal of sucralose as the GAC media was already exhausted. Cotinine is poorly removed by ozone and biodegradation and has shown to breakthrough in an 18‐min EBCT GAC at 12,500 BV (Kennedy, Reinert, Knappe, Ferrer, & Summers, 2015).…”

“…The removal of certain CECs, such as N,N-Diethyl-meta-toluamide (DEET), naproxen, and ibuprofen, has been shown to be improved with a higher EBCT of 14 min compared to 5 min in biofilters containing anthracite (Hallé, Huck, & Peldszus, 2015), demonstrating that these compounds are primarily removed by biodegradation. There are other studies showing the importance of BAC in the biodegradation of CECs (Abromaitis, Racys, van der Marel, & Meulepas, 2016;Greenstein, Lew, Dickenson, & Wert, 2018;Nugroho, Reungoat, & Keller, 2010). Furthermore, although GAC units are intended to sorb CECs, in fact, they will be readily colonized by microorganisms that could also contribute to CEC removal (Rattier, Reungoat, Gernjak, Joss, & Keller, 2012).…”