Analysis of Emerging Constituents in an Activated Sludge Treatment Facility
Authors: Sigurdson Ryan Abigail Mae 
Published: July 2024

Emerging constituents (ECs), or contaminants of emerging concern (CECs), are pharmaceuticals and personal care products (Contaminants of Emerging Concern including Pharmaceuticals and Personal Care Products | US EPA, 2023). The primary source of ECs in surface waters is the discharge from wastewater treatment facilities (WWTF) (Kumar et al., 2022). Little is known about the effects treatment processes have on ECs. Research regarding ECs has increased due to the threats they pose to the environment and human health (Khan et al., 2021). This research aimed to expand understanding ECs’ fate through an activated sludge WWTF. This was accomplished by studying concentrations present in the wastewater after each treatment step and testing for statistically significant removals and temporal variation. Eleven constituents from varying drug classes and personal care products were analyzed. The selected ECs were categorized into three groups (1) over-the-counter drugs and personal care products (acetaminophen, ibuprofen, and salicylic acid); (2) common prescription drugs (albuterol, cimetidine, methylphenidate, and theophylline); and (3) specialized prescription drugs (citalopram, primidone, sulfamethoxazole, and warfarin).

The sampling process was completed over six months, from February to July 2022, at the Lander Street Water Renewal Facility (LSWRF). This research is unique in that each step in the treatment process was analyzed, including the solids treatment process. EC concentrations were analyzed by liquid chromatography and mass spectrometry (LC/MS).

Three major trends in the liquid and solids results were identified: significant reductions, sequestering and release, and continuous release. Significant reductions were exhibited by six constituents: acetaminophen, ibuprofen, salicylic acid, theophylline, and sulfamethoxazole. Reductions were primarily from the biological treatment, and the net reductions ranged from 90.7% to 99.8%. Sequestering and release were exhibited by three constituents (albuterol, cimetidine, and primidone) in that concentrations were reduced following biological treatment, increased after secondary clarification, and varying degrees of reduction through the remaining treatment processes. It is believed that microorganisms sequester and are unable to uptake constituents as they do with phosphorus. Subsequently, the microorganisms release constituents in the secondary clarifier. This resulted in minimal net reductions of the constituents ranging from 13.6% to 58.6%. The continuous release was exhibited by methylphenidate and citalopram from the influent to secondary clarification, which is believed to be due to parent compounds breaking down and releasing them into the system. The solids results did not mirror the liquid's and exhibited a continuous reduction across solids sample locations. This reduction is believed to be due to constituent break down to a metabolite or being biologically transformed into the liquid phase. Citalopram exhibited little net reduction (0.75%), and methylphenidate exhibited a 53.3% net increase. Warfarin was not detected in liquid or solids samples due to low LC/MS sensitivity.

Student’s t-tests of temporal variations found four ECs with significantly different liquid concentrations (albuterol, cimetidine, citalopram, and primidone and one EC with statistically different solids concentrations (acetaminophen). It was concluded that temporal variations in albuterol and acetaminophen were likely due to seasonal usage. It is difficult to conclude if the variation is due to wastewater variability or from the temporal variation with this limited dataset. There are no direct indicators for temporal variations of cimetidine, citalopram, and primidone. It was concluded that the ECs’ variation is due to the variability of the wastewater.

This research expanded the understanding of ten detected ECs in the LSWRF. It determined four constituents with significant reductions and identified ECs with increased concentration through the facility. Conclusions of temporal variations were also formulated. It is recommended that further research be conducted concerning ECs due to the threat they pose to the environment and human health despite this study answering the identified research questions.