No abstract

Microbial consortia are effective biofilters to treat wastewaters, allowing for resource recovery and water remediation. To re-use and save water in the domestic cycle, we assembled a suspended biofilm, a ‘biofilter’ to treat dishwasher wastewater. Bacterial monocultures of both photo- and hetero-trophs were assembled in an increasingly complex fashion to test their nutrient stripping capacity. This ‘biofilter’ is the core of an integrated system devoted to re-using and upcycling of reconditioned wastewater, partly in subsequent dishwasher cycles and partly into a vertical garden for plant food cultivation. The biofilter has been assembled based on a strain of the photosynthetic, filamentous cyanobacterium Trichormus variabilis, selected to produce an oxygen evolving scaffold, and three heterotrophic aerobic bacterial isolates coming from the dishwasher wastewater itself: Acinetobacter, Exiguobacterium and Pseudomonas spp. The consortium has been constructed starting with 16 isolates tested one-to-one with T. variabilis and then selecting the heterotrophic microbes up to a final one-to-three consortium, which included two dominant and a rare component of the wastewater community. This consortium thrives in the wastewater much better than T. variabilis alone, efficiently stripping N and P in short time, a pivotal step to the reuse and saving of water in household appliances.

The structural characteristics of diatom cell walls (frustules) has led to their widespread use in diverse biotechnological applications, some of which can be further improved by surface chemical modification (functionalization). The use of coating agents can significantly increase surface binding capacity for target compounds. Frustules of the diatom Staurosirella pinnata used here were a by-product after applying a cascade-extraction process (for other products) to mass cultures. The protocol for the cleaning and functionalization of raw frustules using 3-Mercaptopropyl-trimethoxysilane and 3-Aminopropyl-trimethoxysilane was optimized and reported. Functionalization efficacy was observed using Electron Microscopy, Energy Dispersive X-ray Spectroscopy and Fourier-Transform Infrared Spectroscopy. Optimally functionalized frustules were evaluated for nickel removal from aqueous solutions. Incubations of 10 min, using 1 g/L of frustules, gave almost complete Ni removal with functionalized frustules compared to 3% removal by raw frustules. The proposed protocol represents a reproducible and efficient alternative for Ni removal from contaminated water.