In tomato processing plants, the production of paste involves the use of heat to evaporate water to concentrate the tomato juice. The hot water isolated from the juice is then passed through cooling towers to cool it sufficiently before discharge. Recovery of excess and blowdown water from the cooling towers would decrease the net water demand of the plant and improve water efficiency. However, since this water has been exposed to the open air, it must be disinfected before reuse. This research investigated the use of a novel ultraviolet (UV) system to disinfect water from the cooling tower basins located at an industrial tomato processing facility. The objective was to assess, in situ, the disinfection system’s performance with regards to its utility, and its ability and to treat wastewater generated in an operational, industrial-scale setting. Beyond typical wastewater microbial assays, 16S rRNA gene sequencing was employed to understand the bacterial communities present in the wastewater, and to screen for microorganisms that may pose a risk for water reuse in food processing facilities.

We present a novel system for water disinfection with ultra-violet (UV) radiation. In this system, the UV lamps do not come into contact with the water and hence remain free of fouling. The system incorporates a diffusor and a nozzle, with stationary guide vanes built into each. Their combined purpose is to reduce the hydraulic losses while imparting a strong swirl component to the flow. The swirl significantly enhances turbulent mixing processes and provides a self-cleansing mechanism that renders the system tolerant to high levels of turbidity and scaling. The hydrodynamic performance of the system was optimized using Computational Fluid Dynamics, while the manufacture of its key components was accomplished using advanced mechanical design software and three-dimensional (3D) printing. Biodosimetry testing with the bacteriophage MS2 indicated the delivery of a UV dose of 215.6 mJ/cm2. This produced a 6.9 log10 reduction of E. coli and 7.12 log10 reduction of MS2. Assessment of the system with hard water containing high Ca, Mg, and Fe concentrations, and with water with turbidity of 18 NTU indicated that the log10 removal of E. coli remained above 5.

Reliable, robust, and inexpensive disinfection systems are needed to expand water security in remote and underserviced areas. This paper reports on the deployment and evaluation of a novel UV water disinfection system in a remote rural community. Prior laboratory tests indicated a 7.12 log10 reduction of the bacteriophage MS-2 at a flow rate of 9.46 L/min, which corresponds to a supplied UV dose 215 mJ/cm² . Further tests in water containing turbidity levels up to 18 NTU showed E. coli removal remaining above the 5 log10 level. Field testing was performed at a Native American reservation in Northern California where the system was used to treat groundwater obtained from a well with a known fecal contamination. The system was powered by solar panel and was operated on-demand for extended periods. Tests on the treated water showed that the system exceeded the standard of disinfection required for drinking water. PRACTITIONER POINTS: A novel system for water disinfection with UV light is described. Laboratory and field tests showed high levels of disinfection achieved even at low UVT and high turbidity. System is robust, reliable and inexpensive to produce thus suitable for use in underserved communities.

Untreated recycled irrigation water has been shown to introduce and spread plant pathogens such as Pythium and Phytophthora in commercial nurseries. Nevertheless, few nurseries currently treat their recycled irrigation water. Instead, nurseries use prophylactic pesticides to control the spread of plant pathogens, which increases costs and promotes the growth of resistant pathogens. Of interest to California is the spread of Phytopthora ramorum, causal agent of Sudden Oak Death (SOD), responsible for the death of tens of thousands of trees in California and Oregon. This study investigated the use of a novel UV disinfection system to inactivate P. ramorum and other microbial contaminants at the National Ornamental Research Site at the Dominican University of California (NORS-DUC). In this system, the UV lamps do not come in contact with the water and hence remain free of the ‘lamp fouling’ problem. Tests on waters having the same characteristics as run-off from commercial nurseries showed a minimum of 3.7 log removal of bacterial species, 91.7% reduction of fungal counts, and 100% inactivation of the P. ramorum in the effluent. Treating the run-off from plant nurseries limits the spread of plant pathogens and enables the onsite re-use of the run-off.

The contribution of planktonic cyanobacteria to burial of organic carbon in deep-sea sediments before the emergence of eukaryotic predators ~1.5 Ga has been considered negligible owing to the slow sinking speed of their small cells. However, global, highly positive excursion in carbon isotope values of inorganic carbonates ~2.22-2.06 Ga implies massive organic matter burial that had to be linked to oceanic cyanobacteria. Here to elucidate that link, we experiment with unicellular planktonic cyanobacteria acclimated to high partial CO₂ pressure (pCO₂) representative of the early Paleoproterozoic. We find that high pCO₂ boosts generation of acidic extracellular polysaccharides (EPS) that adsorb Ca and Mg cations, support mineralization, and aggregate cells to form ballasted particles. The down flux of such self-assembled cyanobacterial aggregates would decouple the oxygenic photosynthesis from oxidative respiration at the ocean scale, drive export of organic matter from surface to deep ocean and sustain oxygenation of the planetary surface.