Aerobic Granular Sludge: Assessing PPCP Removal From Wastewater
Catherine Kirkland | Montana State University
Pharmaceuticals and personal care products (PPCPs) are increasingly recognized as emerging environmental contaminants around the world, in part because their presence in the environment may contribute to microbial antibiotic resistance and hormonal disruptions in aquatic species. PPCPs, like antibiotics and hormones found in human and livestock excreta, enter the environment primarily via wastewater and stormwater runoff.
Fortunately, at this time the human health risks of PPCP contamination in the environment appear to be low. However, population growth, increasing PPCP use by the public, and projections for water scarcity in the future suggest that risks to human health may increase over time. Aerobic granular sludge (AGS) is emerging as a significant challenger to the dominance of traditional suspended growth technologies like conventional activated sludge (CAS) for treatment of municipal and industrial wastewaters. Aerobic granules are biofilms which grow without a carrier material; mixed microbial populations form aggregates several millimetres in diameter. The size and structure of the granules promote metabolic diversity and simultaneous biochemical conversions of soluble wastewater constituents due to substrate and oxygen gradients within the granular biomass.
The proposed research will use laboratory-scale AGS sequencing batch reactors (SBRs) seeded with lab-grown granules. A negative control reactor and an experimental SBR will receive synthetic wastewater with target PPCPs in relevant concentrations added to the experimental reactor. High performance liquid chromatography (HPLC) coupled with quantitative time-of-flight mass spectrometry (QTOF-MS) will assess and quantify the presence of PPCPs and known biodegradation products in the aqueous phase and within the granular biomass. In addition, bulk measurements of influent and effluent organic carbon and nutrient concentrations will be made routinely to monitor the reactors’ treatment efficiency, and high throughput sequencing of the 16S gene ribosomal RNA will be applied periodically to sludge samples to monitor changes in the microbial community. Fluorescence confocal scanning laser microscopy (CLSM), magnetic resonance microscopy (MRM) and other microscopy methods will be used to compare the morphology and structure of granules exposed to PPCPs to control granules.
This ongoing and proposed research uses a novel wastewater treatment biotechnology, aerobic granular sludge (AGS), to explore its capacity to reduce future loads of PPCPs entering the environment while maintaining high effluent quality with respect to conventional wastewater contaminants. I hypothesize that the biofilm structure of AGS provides a means to remove complex contaminants like PPCP(s) via sorption to the sludge phase and bio-degradation. In addition, the proposed research examines how the presence of PPCP(s) in the wastewater influences treatment efficiency, the physical stability of the granular biomass, and the microbial community. The proposed project entails operation of bioreactors in MSU’s Center for Biofilm Engineering to acquire preliminary data and refine research hypotheses for subsequent proposals. Project goals include:
- Quantify PPCP removal from the aqueous phase in a laboratory AGS reactor.
- Quantify sorption of PPCP to AGS samples from the experimental reactor.
- Compare treatment efficiency for traditional wastewater constituents (carbon, nitrogen, and phosphorus) between the control (SBR-1) and experimental (SBR-2) reactors, and monitor microbial community evolution.