qPCR-Based Monitoring of 2-Methylisoborneol/Geosmin-Producing Cyanobacteria in Drinking Water Reservoirs in South Korea.

Cyanobacteria can exist in water resources and produce odorants. 2-Methylisoborneol (2-MIB) and geosmin are the main odorant compounds affecting the drinking water quality in reservoirs. In this study, encoding genes 2-MIB (mic, monoterpene cyclase) and geosmin (geo, putative geosmin synthase) were investigated using newly developed primers for quantitative PCR (qPCR). Gene copy numbers were compared to 2-MIB/geosmin concentrations and cyanobacterial cell abundance. Samples were collected between July and October 2020, from four drinking water sites in South Korea. The results showed similar trends in three parameters, although the changes in the 2-MIB/geosmin concentrations followed the changes in the mic/geo copy numbers more closely than the cyanobacterial cell abundances. The number of odorant gene copies decreased from upstream to downstream. Regression analysis revealed a strong positive linear correlation between gene copy number and odorant concentration for mic (R2 = 0.8478) and geo (R2 = 0.601). In the analysis of several environmental parameters, only water temperature was positively correlated with both mic and geo. Our results demonstrated the feasibility of monitoring 2-MIB/geosmin occurrence using qPCR of their respective synthase genes. Odorant-producing, gene-based qPCR monitoring studies may contribute to improving drinking water quality management.

Prediction of varying microcystins during non-thermal plasma oxidation of harvested microalgal biomass.

By capturing intracellular microcystins (MCs) release from microalgal cell destruction and extracellular MCs oxidation, this study suggests a mathematical model explaining the simultaneous removal of microalgae and their toxins (MC-LR, -RR, and -YR) in non-thermal plasma (NTP) application. Although the suggested model was built based on simplified kinetic assumptions, it can reasonably predict the behavior of extracellular MCs in a harvested/concentrated slurry of microalgae taken from a blooming site. After 24 h of NTP treatment, the experimental reduction of extracellular MCs was recorded up to ∼77 %. Regressions based on the experimental data reveal the degradation rate (8.60 d-1) and release rate (0.37 d-1) of MCs, which provides the essential physicochemical information about intracellular MCs release by microalgal cell destruction. Simulation results help to develop safe and useful control over the simultaneous treatment of harvested microalgal biomass and toxins. This study further demonstrates that the suggested model contributes to predicting the variation of MCs in mass management of microalgal biomass for sustainable utilization.

Coupling cold plasma and membrane photobioreactor for enhanced fouling control during livestock excreta treatment.

To treat high-turbidity livestock excrements (LE), this study suggests a synergistic system coupling cold plasma (CP) and membrane photobioreactor (MPBR). During the continuous operation of the integrated system, physico-chemical oxidation of CP decompose turbidity and total suspended solids (TSS) up to 99.9%. The microalgal concentration of Scenedesmus obliquus in the following MPBR reach as high as 1,944 mg D.W./L, which indicates the residual organic and inorganic substances were actively consumed by phototrophic metabolism. Pearson correlation analysis confirms this synergistic relationship of turbidity and TSS with biological growth parameters such as biomass growth, soluble microbial products, and extracellular polymeric substances. Results evidence that the turbidity and TSS are directly connected to the microalgal growth in this integrated system thus the role of CP is crucial to achieving the LE treatment goal. Overall, this study provides a guideline to support the enhanced treatment strategy to control LE with the production of bioresources for sustainable carbon and nutrient cycles.

Integration of submerged microfiltration and cold plasma for high-strength livestock excreta.

Numerous biological treatment techniques have been studied for better management of high-strength livestock urine and manure (LUM) but it is still challenging. To gain an advanced option for LUM management, this study proposes a physicochemical process combining microfiltration (MF) and cold plasma (CP). Experimental design applying single CP, single MF, and the integrated system coupling CP and MF (CP + MF) evaluates the performances of the configurations while reducing hydraulic retention time (HRT) from 3 d to 1 d. Results demonstrate that the CP + MF can maximize the removal efficiencies of total nitrogen (72.4 %), total phosphorus (57.8 %), NH4-N (73.3 %), turbidity (99.1 %), dissolved organic carbon (71.3 %), suspended solids (98.7 %) at HRT 3 d. It was verified that CP, even at the lowest HRT (1 d), significantly reduces membrane resistance (0.4 × 1014 m-1) compared to the control (1.5 × 1014 m-1) which leads to lower transmembrane pressure (TMP, 45.6 kPa) and inclined flux (4.4 L/m2/h) than those of the control (45.6 kPa TMP and 2.2 L/m2/h). These results contribute to the advanced treatment of LUM with a cost-effective and environmentally friendly strategy via technical convergence.