Microalgae cultivation in wastewater effluent from tilapia culture pond for enhanced bioethanol production

The large number of wastewaters are generated because of the various production processes. Vegetable and fish processing can be considered an important industry for wastewater generation. The essential method for completing this waste is to digest the organic matter using anaerobic digestion followed by aerobic wastewater treatment processes; however, wastewater from tilapia culture pond retains considerable quantities of inorganic substances, particularly nutrients like nitrogen and phosphorus. The optimal conditions for cultivating Chlorella vulgaris from wastewater treatment effluent from tilapia culture pond were investigated in this study. The appropriate conditions were found to be 10% initial stock suspension, 20 cm depth, and 12 days of culture conditions. C. vulgaris had an optical density of 0.649, a cell density of 17.68 × 105 cells/mL, and biomass of 0.376 ± 94.21 mg/L after cultivation. Discharged wastewater from the fishpond was utilized for the improved growth of microalgae and obtained biomass was used for bioethanol production. This study verified that fishpond wastewater is the best source of nutrients for algal mass production and biofuel applications.

Sensitivity of contaminant spread to decay rate in water distribution systems with implications for the spread of emerging contaminants

‘Emerging contaminants’ are newly introduced into the environment through release into surface waters from wastewater treatment effluent, manufacturing, and agricultural use. How emerging contaminants move through water systems is unclear. Since the decay rates of emerging contaminants in piping systems have not been determined, this study determines the importance of decay rate on concentration throughout a distribution system and also determines how the system layout effects concentration. Systems were modeled to determine the time to peak contamination for a clean system becoming contaminated, as well as a contaminated system being cleaned of contamination. It was found that only emerging contaminants with second-order decay at the highest rate observed did not build up to high concentrations. The position of storage tanks in the distribution system affected the rate at which contaminants cleared the system, and systems with a branched layout could be cleared of contamination faster than systems containing loops.

Investigating selection for antimicrobial resistance by non-antibiotic drugs (NADs)

A recent study screening over 1000 drugs has shown that non-antibiotic drugs (NADs), including human targeted drugs, have been shown to have antimicrobial effects on representative strains of human gut bacteria. NADs are present in both wastewater effluent and freshwater systems, where they may only be partially metabolised. Concentrations of antibiotics found in the environment have been shown to select for resistance in complex microbial communities, and it is thought that concentrations of NADs in the environment may also select for resistance. This project aims to determine if NADs select for antimicrobial resistance, by investigating effects in a complex bacterial community. Pharmaceuticals from 7 different drug classes have been screened for antimicrobial activity. The most potent compounds will be used in exposure experiments to identify any existing antimicrobial resistance genes that confer cross-resistance to both antibiotics and NADs using a metagenomics approach. In addition, changes in community composition will be investigated to determine if there is enrichment for opportunistic pathogens after exposure to NADs. This project ultimately aims to inform on environmental water quality standards and environmental risk assessment of wastewater treatment effluent in order to mitigate the growing problem of environmental antimicrobial resistance.

Abundance and Antimicrobial Resistance of Three Bacterial Species along a Complete Wastewater Pathway

After consumption, antibiotic residues and exposed bacteria end up via the feces in wastewater, and therefore wastewater is believed to play an important role in the spread of antimicrobial resistance (AMR). We investigated the abundance and AMR profiles of three different species over a complete wastewater pathway during a one-year sampling campaign, as well as including antimicrobial consumption and antimicrobial concentrations analysis. A total of 2886 isolates (997 Escherichia coli, 863 Klebsiella spp., and 1026 Aeromonas spp.) were cultured from the 211 samples collected. The bacterial AMR profiles mirrored the antimicrobial consumption in the respective locations, which were highest in the hospital. However, the contribution of hospital wastewater to AMR found in the wastewater treatment plant (WWTP) was below 10% for all antimicrobials tested. We found high concentrations (7–8 logs CFU/L) of the three bacterial species in all wastewaters, and they survived the wastewater treatment (effluent concentrations were around 5 log CFU/L), showing an increase of E. coli in the receiving river after the WWTP discharge. Although the WWTP had no effect on the proportion of AMR, bacterial species and antimicrobial residues were still measured in the effluent, showing the role of wastewater contamination in the environmental surface water.