E c o M i c r o

MICROBIOLOGICAL ANALYSIS OF WASTEWATER AND SETUP OF THE MICROBIAL CONSORTIUM

This line of work has been based on the analysis of washing wastewater: washing wastewater from white and coloured laundry was assessed separately, and both chemical analyses were performed to identify the organic load and the amount of nutrients present, as well as microbiological analyses to determine the composition of the microbial community present in the wastewater.

The chemical analyses demonstrated that the wastewater is biodegradable (the COD/BOD₅ ratio is 2) and contains a portion of nutrients that can be reused.

Microbiological analyses were conducted using both standard microbiology techniques (plate cultivation) and molecular techniques. Culture methods combined with Sanger sequencing demonstrated that the wastewater largely contained Enterobacteriaceae (mainly Enterobacter), associated with the intestine, and Aeromonas, ubiquitous and sometimes opportunistic pathogens, present in aquatic environments. The other genera most frequently detected (Micrococcus sp., Terribacillus sp., and Priestia sp.) are ubiquitous bacteria, also potential human colonizers of the intestinal tract and skin. Molecular techniques (DNA metabarcoding in Next Generation Sequencing) confirmed the results of culture methods, namely that the vast majority belong to the Enterobacteriaceae family; the technique also allowed the identification of Pseudomonadaceae, bacterial taxa associated with the intestine or human skin, which are normally present on the clothes washed in the washing machine. The other families detected at high frequency (Moraxellaceae, Aeromonadaceae and Rhodobacteraceae) include ubiquitous species, often also associated with the human respiratory tract, intestine or skin. Interestingly, the data obtained with molecular techniques showed a different taxa prevalence and distribution in wastewater from white or coloured garments, even within the same households. This is understandable, given the different types and uses of white (household linens, shirts, etc.) and coloured garments (underwear, knitwear, delicates, etc.).

The results indicate that the microorganisms present in the wastewater are predominantly those associated with clothing, and does not seems to be a specific community settled in washing machines. This finding is consistent with the literature, which shows that the composition of the washing machines microbial community depends primarily on the users and not on the type of washing machine or its geographical location (Jacksch et al., 2019; Abney et al., 2021; Whitehead et al., 2025).

Similarly to previous experiments on dishwasher wastewater (Alabiso et al., 2023), microbes isolated by culture were collected and used in microbial consortium assembly trials, which represent the basis of the biological filter. According to the results of one-to-one tests, one-to-three consortium was constructed by assembling the photosynthetic cyanobacterium T. variabilis with the three heterotrophic bacteria isolated from washing wastewater (Terribacillus sp., Micrococcus sp., Aeromonas sp.), which showed the best performance in the association with the autotrophic cyanobacterium. Unfortunately, none of the heterotrophic bacteria from the washing machine wastewater efficiently associated with T. variabilis, and no consortia were formed.

The failure to form a microbial consortium is due both to the fact that these bacteria are closely related to humans and to the relatively low amount of nutrients present in the wastewater. In fact, none of the microorganisms present has been able to efficiently associate with the autotroph to form the consortium, and the wastewater did not contain enough nutrients to support a microbial consortium. 

 

	THE RESEARCH TEAM
Roberta Congestri
	Associate Professor at the University of Rome Tor Vergata, Department of Biology, where she coordinates the Biology of Algae Laboratory. Her research focuses on microalgae, with a particular interest in taxonomy, ecophysiology, and monitoring of microalgae and cyanobacteria. In the project she deals with the development of the microbial consortium.
Valerio Cantelmo
Research Fellow of the Project. Biotechnologist, he deals with the development of the ad hoc microbial consortium to rehabilitate washing machine wastewater. He also collaborates to the Zero Mile© project, based on a microbial consortium capable of rehabilitating dishwasher wastewater.