Treatment and Toxicity Takeaways From Two Pharmaceutical Wastewater Treatability Studies

Background
Pharmaceutical wastewaters can present a challenge in meeting either pretreatment or surface water discharge requirements. These wastewaters typically contain active pharmaceutical ingredients (APIs) as well as other organic compounds involved in formulating pharmaceutical products. APIs specifically can have targeted effects on aquatic toxicity that may impact permit requirements. Water quality can vary significantly, depending on facility size and product formulation schedules. Unlike many classes of contaminants, APIs vary widely in chemical structure. The uniting factor for APIs is that they actively interact with biological systems in a targeted manner. As a result, many APIs have downstream aquatic toxicity impacts, sometimes at parts per trillion (ppt) concentrations, so treatment targets for whole effluent toxicity (WET) may need to be considered. Treatment processes commonly deployed for API treatment include granular activated carbon (GAC) adsorption, biological processes, and advanced oxidation. Combinations of technologies can also be effective. Oxidation upstream of either biological treatment or GAC adsorption can improve efficacy by breaking down large organic molecules into smaller by-products that could then be more easily removed by biological treatment and/or GAC (Wu, Zhou, Sun, & Fu, 2018; Lhotsky, Krakorova, & et al., 2017). Biological treatment of complex organic compounds is typically more effective in a fixed-bed system than in suspended growth systems like activated sludge (Dvorak, Lederer, Jirku, Masak, & Novak, 2014; Zearley & Summers, 2012). In a biological activated carbon (BAC) process, the sorption capacity of the activated carbon binds pollutants and enables biodegradation processes that would otherwise be too slow to occur in a similarly sized system without GAC. By making GAC adsorption into a biological process, BAC improves micropollutant removal and reduces carbon changeout frequency (Sbardella, Comas, Fenu, Rodriguez-Roda, & Weemaes, 2018).
Objectives The objectives of this study are to synthesize lessons learned from testing and designing wastewater treatment solutions for two different water sources:
1. Groundwater impacted by pharmaceutical operations
2. Equipment rinse waters from pharmaceutical production lines We evaluated both projects through feasibility and treatability studies and are currently in design and contracting phases.
Treatability Case Study #1 The first case study addressed treatment of groundwater impacted by both APIs and VOCs. The extracted water also contained relatively high concentrations of iron, which complicated treatment processes. We conducted a preliminary feasibility study and suggested the use of iron pretreatment followed by BAC pressure vessels. We then designed and operated a six-month pilot test to evaluate the selected treatment train for its ability to meet pretreatment requirements for the local POTW. The BAC was operated similar to a GAC pressure vessel, with regular backwashing to limit biomass buildup and associated fouling. Orthophosphate present in the source water removed the need for micronutrient supplementation to support biological growth in the BAC vessels. General water chemistry and field parameters were monitored in influent and effluent from each process in the treatment train on a weekly basis throughout the life of the pilot. BAC treatment typically requires several months of acclimation before steady-state conditions and an adapted microbial community is established, which is needed to achieve consistent and predictable degradation of APIs and other constituents. Steady-state conditions, as reflected by consistent removal of bulk parameters COD and iron was achieved after three months. Over 99% removal of VOCs and 85% removal of most APIs measured were measured during steady-state conditions, as summarized in Table 1. In addition, pilot-scale treatment reduced whole-effluent toxicity (WET) impacts to Ceriodaphnia dubia and Pimephales promelas relative to influent water, with treated waters exhibiting no measured toxicity for acute survival, chronic survival, and chronic reproduction endpoints. WET outcomes are summarized in Table 2. The removal efficiencies and WET results were sufficient to meet pretreatment requirements and to secure a pretreatment discharge permit for the system. This treatment was also expected to meet surface water discharge requirements. Lessons learned from pilot operations resulted in several design changes prior to detailed full-scale design, including increased backwashing frequency, inclusion of a backwash clarifier, and an additional iron removal pretreatment step.
Treatability Case Study #2 For the second case study, Barr helped a client develop a management strategy for equipment rinse waters from a planned pharmaceutical product line. The API used in this case had significant aquatic toxicity impacts at parts per trillion levels, and needed to be removed to below those levels prior to sewer discharge. Barr coordinated bench-scale evaluation of seven treatment technologies: - Particulate filtration, - Ultrafiltration - Alkaline degradation, - Granular activated carbon (GAC) adsorption, - Electrochemical oxidation (with and without RO post-treatment), - Thermal evaporation, and - Vacuum distillation. Evaluation for full-scale application included bench testing, coordination of whole effluent toxicity (WET) and respirometry testing of treated waters, and a detailed water balance of the proposed full-scale system. Respirometry testing used the secondary influent and biomass from the local POTW and spiked it with varying levels of pharmaceutical wastewater to gauge the effect of the discharge on activated sludge microbes at the POTW. Particulate filtration, ultrafiltration, alkaline degradation, and GAC adsorption did not demonstrate compliance with City toxicity metrics. Electrochemically oxidized water was close to meeting toxicity metrics alone and did meet metrics when paired with reverse osmosis membrane separation treatment of oxidized effluent. However, electrochemical oxidation was more expensive than the two evaporative technologies evaluated, thermal evaporation and vacuum distillation. Performance of tested treatment options with respect to API removal, WET outcomes, and respirometry outcomes are summarized below in Table 3. Estimated capital and operating costs for thermal evaporation options as well as proposed option for enhanced UF treatment are compared on Figure 2. Costs for each option were evaluated with and without a final concentration step to reduce residual management needs. Relative to other options, thermal evaporation was associated with lower project risks associated with discharge and disposal and had a more favorable cost profile. Vacuum distillation may have been more cost effective if there had been a use for high-purity water produced by the process.
Significance and Takeaways Case Study 1 saw effective removal of VOCs and APIs and sufficient toxicity reduction using iron pretreatment followed by fixed-bed BAC vessels. However, treating wastewater for discharge in Case Study 2 proved either ineffective at meeting toxicity requirements or more costly than thermal evaporation options for zero-liquid discharge. General takeaways relevant to other pharmaceutical wastewater applications include: - Whole effluent toxicity is frequently a limiting parameter for pretreatment requirements in pharmaceutical wastewater. - Individual APIs have different amenabilities to water treatment processes and in some cases, evaporation or disposal can be more cost-effective than water treatment and discharge. - APIs often occur in mixtures with other APIs and/or co-contaminants, which can require multiple treatment processes.