Phosphate removal from return liquor of municipal wastewater treatment plant using iron-reducing bacteria

Abstract

The application of iron-reducing bacteria (IRB) for phosphate removal from return liquor (liquid fraction after activated sludge digestion and anaerobic sludge dewatering) of municipal wastewater treatment plant was studied. Methods and Results: Enrichment culture and two pure cultures of IRB, Stenotrophomonas maltophilia BK and Brachymonas denitrificans MK identified by 16S rRNA gene sequencing, were produced using return liquor of WWTP as carbon and energy source and iron hydroxide as oxidant. The final concentration of phosphate increased from 70 to 90 mg l-1 in control and decreased from 70 to 1 mg l-1 in experiment. The mass ratio of removed P to produced Fe(II) was 0.17 g P g-1 Fe(II). S. maltophilia BK showed the ability to reduce Fe(III) using such xenobiotics as diphenylamine, m-cresol, 2,4-dichlorphenol and p-phenylphenol as sole source of carbon under anaerobic conditions. Bacterial reduction of ferric hydroxide enhanced phosphate removal from return liquor. Significance and Impact of Study: An ability of facultative anaerobes Stenotrophomonas maltophilia BK and Brachymonas denitrificans MK to reduce Fe(III) was shown. These bacteria can be used for anaerobic removal of phosphate and xenobiotics by bacterial reduction of ferric ions.