The effects of caffeine, gliclazide, and prazosin on the performance and microbial diversity in an up-flow anaerobic sludge blanket (UASB) reactor

A laboratory-scale up-flow anaerobic sludge blanket (UASB) reactor was deployed in this study to examine the relationship between pharmaceutical compounds and anaerobic process performance. The reactor successfully biotransformed up to 87–99% of psychostimulant caffeine, anti-diabetic drug gliclazide, and anti-hypertensive drug prazosin during 92 days of operation. At the same time, fluctuations were recorded for the methane gas production, and also the domination of acetic acid and propionic acid in the presence of pharmaceutical compounds was measured. The results from 16s rRNA sequencing revealed that these compounds stimulated the growth of hydrogenotrophic methanogens, mainly Methanobrevibacter and Methanobacterium, while shifting the compositions of hydrolytic and fermentative bacteria. These outcomes proved the capability of the pharmaceutical compounds to influence the process performance by changing the microbial compositions in the anaerobic reactor

Biotransformation of caffeine, gliclazide and prazosin in an up-flow anaerobic sludge blanket reactor

Up-flow anaerobic sludge blanket (UASB) reactors are largely utilised as an anaerobic reactor configuration to efficiently treat various wastewater streams. However, previous UASB operations for the removal of pharmaceutical compounds at low hydraulic retention time (HRT) resulted in poor chemical oxygen demand (COD) and removal efficiencies for the investigated compounds. Anaerobic process performance has also been found to be vulnerable towards pharmaceutical compounds at high concentration levels but there is no evidence to indicate if the same effects will be induced when other compounds are present at trace concentration levels. This research aims to establish the relationship between pharmaceutical compound removal, influencing parameters, and anaerobic process performance. In this research, caffeine, gliclazide, and prazosin were selected based on their environmental occurrences, persistency, and toxicity. The compounds were investigated as a mixture to simulate their concurrent occurrences in the same actual wastewater stream. The first part of the research investigated the biodegradability of the three compounds in an anaerobic batch experiment. Synthetic wastewater and inoculum mixture were spiked with 1 mg/L of mixed pharmaceutical compounds and incubated at mesophilic condition (37°C) for 90 days. All compounds achieved removal through biotransformation between 44 - 99% by the end of the incubation period. The second part of the research was commenced by running five experimental phases in an acclimatised laboratory-scale UASB reactor. Phases I - V were carried out to assess the effect of pharmaceutical concentrations (0.1 – 1 mg/L), HRT (36 – 48 hours) and different reducing conditions (predominant methanogenic and simultaneously reducing conditions) to the removal of pharmaceutical compounds and UASB process performance. Overall, biotransformation remained the predominant removal pathway in the laboratory-scale experiments despite the changes in pharmaceutical concentrations and HRT. Only gliclazide recorded an improvement of biotransformation up to 99% under simultaneous reducing conditions compared to that in predominant methanogenic conditions. The UASB reactor was also operating in a stable condition (COD removal efficiency of 93 ± 2%) but fluctuations were recorded in the production of individual volatile fatty acids (VFAs) and biogas. Microbial assessment through 16s rRNA sequencing justified the changes in VFAs production based on the effect of the pharmaceutical compounds towards the growth of hydrolytic and fermentative bacteria. The compounds also shifted the composition of methanogenic archaea by favouring hydrogenotrophic methanogens (59 - 72%) over acetoclastic methanogens (15 - 31%) under predominant methanogenic conditions

Can anaerobic intermediate stages affect the biotransformation and sorption of pharmaceutical compounds?

Batch experiment was conducted to investigate if anaerobic intermediate stages can affect bio-transformation and sorption performance of selected pharmaceutical compounds (stimulant caffeine (CAF), anti-diabetic drug gliclazide (GCZ) and anti-hypertensive drug prazosin (PRZ)). The outcome revealed that CAF was removed solely via biotransformation and followed the methanogenic pathway. Sorption was significant during the fermentation stage for hydrophobic GCZ and PRZ although both compounds continued to biotransform in the later stage of incubation. While more than 95% removal of all compounds was achieved after 30 d of incubation under anaerobic mesophilic condition, further incubation to Day 90 resulted in re-occurrences of GCZ and PRZ in the aqueous and solid phase. Biotransformation of hydrophilic and hydrophobic compounds could not be represented in the same kinetic model considering sorption and retransformation dis-played significant effect to the model. This study also reported the first removal of GCZ and PRZ under anaerobic condition