Activated Sludge Biomass as Magnetic Biosorbent

Abstract

Background. Heavy metal pollution is a typical issue for a number of industries, and their removal is crucial for the environmental ecology. Biomass can be used as cheap and eco-friendly sorbent, for example excess activated sludge, because its utilization is a major expense in water treatment. Sorbents with magnetic properties can be extracted using fast and efficient magnetic separation method. Mechanism of biomineralization biogenic magnetic nanoparticles (BMN) is proved to be general for all three domains, so it is important to study what amount of activated sludge microorganisms are potential BMN producents. Objectives. The objective of this study is to determine potential BMN producents among microorganisms of activated sludge using methods of comparative genomics, to obtain magnetic biosorbent and investigate its efficiency in Fe 2+ removal from FeSO 4 solution (500 mg/L). Methods. For estimating homologies between biomineralization proteins of Μ agnetospirillum gryphiswaldense MSR-1 and microorga­nisms of activated sludge were used methods of pairwise and multiple genomic sequence alignment using free access tool BLAST (National Centre for Biotechnological Information, USA). For obtaining magnetic sorbent from activated sludge biomass high gradient magnetic separation was used. Results. Bioinformatic analysis showed, that among studied microorganisms of activated sludge, whose genomes are sequenced per 25% and more, all appeared to be potential BMN producers ( Stentor coeruleus , Bodo saltans , Sphaerotilus natans , Beggiatoa alba B18LD, Oscillatoria acuminata PCC 6304, Oscillatoria sp. PCC 10802, Oscillatoria nigro-viridis PCC 7112, Rivularia sp. PCC 7116, Anabaena sp. CRKS33, Anabaena sp. WA113, Anabaena sp. AL93, Anabaena sp. PCC7108, Anabaena MDT 14b, Thiothrix nivea DSM 5205, Duganella zoogloeoides ATCC 25935), 12 of them – potential producents of intracellular crystalline BMN. It was shown, that Fe 2+ removal efficiency isequal for non-separated activated sludge and both magnetic and non-magnetic fractions. Conclusions. Results show that excess sludge biomass can be used to obtain magnetic sorbent, which can be made without the use of extra magnetization with artificial magnetic nanoparticles. This allows extracting sorbent using methods of high gradient magnetic separation. Sorption results of Fe 2+ for magnetically labelled biosorbent on the base of activated sludge microorganisms experimentally proves equal efficiency of magnetically labelled, non-labelled fractions and biomass which was not exposed to HGMS and is higher than 97%.