Organic wastewater treatment without greenhouse gas emission by photosynthetic bacteria

High conversion of wastewater into biomass of photosynthetic bacteria was investigated. This biomass is possibly utilized as feed for fish or extraction source of PHA (polyhydroxyalkanoate). As a fundamental investigation, batch experiments were carried out using purple nonsulfur bacteria Rhodobacter sphaeroides to determine the growth rate and yield and to quantify CO2 release/uptake during substrate assimilation. The substrates used for this study were five kinds of VFA namely, acetate, propionate, n-butyrate, n-valeric acid and n-caproate. Growth rates for n-valeric acid and n-cvaproate were lower than those for other VFAs. Yields, defined as carbon in bacteria divided by removed organic carbon, for n-butyrate, n-valeric acid and n-caproate exceeded 1 due to simultaneous CO2 uptake and no net greenhouse gas emission. Maximum CO2 uptake was 17% of removed DOC (dissolved total organic carbon) in the case of n-valeric acid supplemented with 2.00 g/l of NaHCO3.