Wastewater bioremediation with using of phototrophic non-sulfur bacteria Rhodopseudomonas yavorovii IMV B-7620

Abstract

Phototrophic purple non-sulfur bacteria (PNSB) mineralize organic waste. In media with different organic substances they are metabolized from simple aliphatic organic acids to complex polysaccharides. These bacteria can produce H2, indole-3-acetic acid and 5-aminolevulinic acid. PNSB purify waters from hydrogen sulfide and, as components of ecosystem trophic chains, participate in process of sulfur cycle. The ability of these bacteria to denitrification is of particular interest to specialists because nitrates concentrations in industrial effluents are often much higher than the maximum permissible concentrations. The use of industrial, agricultural and household wastes to produce PNSB biomass is economically profitable. Therefore, the aim of our work was to investigate the influence of wastewater of the yeast plant and the water of the settler № 3 filtrate of the Lviv Solid Household Waste Landfill (LSHWL) on the biomass accumulation by PNSB Rhodopseudomonas yavorovii IMV B-7620 and the changes in the composition of these waters in the process of cultivation of the investigated bacteria. Bacteria were grown for 21 days anaerobically at an illumination intensity of 200 lux in 500 ml flasks at +29 ... +30 °C. The wastewater of the yeast plant and the water of the settler № 3 filtrate of the LSHWL were used as the cultivation media. Water was diluted at 10; 30; 50; 100 times. In water, diluted at 10 times, the pH, total ferrum content, Ca2+, Mg2+, Cl-, NO3-, NO2-, SO42-, HS- and chemical oxygen demand (COD) were determined. The biomass of bacteria was measured turbidimetrically at λ = 660 nm. The concentration of HS- was determined spectrophotometrically (λ = 665 nm) by the formation of methylene blue. The content of sulfate ions was determined turbidimetrically (λ = 520 nm) after their precipitation with barium chloride. The concentrations of Ca2+ and Mg2+ were determined titrometrically by reaction with trilon B; Na+ and K+ were analyzed by flame emission spectrometry method (lK = 768 nm, lNa = 589 nm). The pH of the water was measured potentiometrically. The concentration of Cl- was determined titrometrically by reaction with AgNO3. The concentration of nitrite ions was determined spectrophotometrically by the method of sulfanilic acid diazotization by nitrite ions and the interaction of the formed salt with n-(naphthyl)ethylenediamine dihydrochloride (λ = 540 nm, l = 10 mm). The concentration of nitrate ions was determined spectrophotometrically by the diazotization method. Zinc powder was used as the reducing agent. COD was measured with using of KMnO4. It is characterised the patterns of biomass accumulation by R. yavorovii IMV B-7620 bacteria in the wastewater of the yeast plant and the water of the settler № 3 filtrate of the LSHWL, diluted at 10–100 times. The optimal dilution (at 10 times) of water for bacteria cultivation was selected. Bacteria R. yavorovii IMV B-7620 accumulate biomass of 2.2 g/l during growth in a yeast plant wastewater that is twice as large as the biomass, accumulated by bacteria in the diluted water of the settler № 3 filtrate. The organic compounds oxidation efficiency of the yeast plant wastewater and of the settler № 3 filtrate of LSHWL, determined by chemical oxygen demand, was 42.3 and 65.6 %, respectively, on the 21st day of cultivation. The established possibility of the influence of R. yavorovii IMV B-7620 on the decreasing of the content of total Fe, Ca2+, Mg2+, NO3-, NO2-, SO42-, Cl-, HS- in wastewater has complemented and broadened the understanding of the role of purple non-sulfur bacteria in ecosystems, which can significantly influence on the biogeochemical cycles of these compounds in nature. The results obtained may form the basis for the development of effective biotechnologies for wastewater treatment from hydrogen sulfide, chlorine, ferrum, nitrogen, sulfur compounds with the participation of these microorganisms.