Silver nanoparticle filter for domestic wastewater reuse

Abstract

BACKGROUND: Under scarcity of freshwater, the reuse and low-cost technological solutions applied to wastewaters seek to reduce contamination to the users and freshwater biota. RESULTS: A low-cost cellulose membrane was doped with silver nanoparticles to filter urban wastewater (UW) from a city in Argentina. The total amount of coliforms and Escherichia coli in the filter decreased by 99.6% and 99.9%, respectively. The leak of silver from the filter was 275 ng L−1, analyzed by square wave anodic stripping voltammetry. Silver nanoparticles tested on HepG2 and A549 mammalian cell lines showed no toxicity in a broad concentration range. Calculation of the organic matter provided by dead bacteria post-filtration was 347 μg L−1 proteins, 148 μg L−1 nucleic acids, 57 μg L−1 lipids, and 53 μg L−1 polysaccharides, indicating high availability of organic matter. The retention of inorganic salts in the filter was 78.5% ammonia, 6.2% nitrates, 97.6% nitrites, and 19.2% phosphates. In post-filtered UW, the Lactuca sativa germination test showed early seed germination between 90% and 95% in all the dilutions tested. In the range of 6.25% to 50.0%, filtered UW showed no significant differences in the hypocotyl but the difference was significant in the radicle length (mm) compared to the control made of synthetic media (P < 0.05). CONCLUSION: The development of a low-cost filter based on cellulose membranes doped with silver nanoparticles allowed the reuse of wastewater for domestic purposes and garden irrigation.