Heterotrophic bacteria proliferate in organic-rich environments and systems containing sufficient essential nutrients. Nitrogen, phosphorus and potassium are the nutrients required in the highest concentrations. The ratio of carbon to nitrogen is an important consideration for wastewater bioremediation because insufficient nitrogen may result in decreased treatment efficiency. It has been shown that during the treatment of effluent from the pulp and paper industry, bacterial nitrogen fixation can supplement the nitrogen requirements of suspended growth systems. This study was conducted using physicochemical analyses and culture-dependent and -independent techniques to ascertain whether nitrogen-fixing bacteria were selected in biological sand filters used to treat synthetic winery wastewater with a high carbon to nitrogen ratio (193:1). The systems performed well, with the influent COD of 1351 mg/L being reduced by 84–89%. It was shown that the nitrogen fixing bacterial population was influenced by the presence of synthetic winery effluent in the surface layers of the biological sand filters, but not in the deeper layers. It was hypothesised that this was due to the greater availability of atmospheric nitrogen at the surface. The numbers of culture-able nitrogen-fixing bacteria, including presumptive Azotobacter spp. exhibited 1–2 log increases at the surface. The results of this study confirm that nitrogen fixation is an important mechanism to be considered during treatment of high carbon to nitrogen wastewater. If biological treatment systems can be operated to stimulate this phenomenon, it may obviate the need for nitrogen addition.
Geyer, Monique; Onyancha, Faith M.; Nicol, Willie; Brink, Hendrik G.(The Italian Association of Chemical Engineering, 2018)
This study investigated the malic acid production capability of Aspergillus oryzae NRRL 3488 with three different
CaCO3 concentrations, 20 g/L, 80 g/L, and 120 g/L, used as pH buffers and CO2 supply. A black box model ...
Mynhardt, Herman; Van Niekerk, Willem A.; Erasmus, L.J. (Lourens Jacobus); Hassen, Abubeker; Coertze, R.J. (Roelof Johannes)(Escola Superior de Agricultura, 2016-11)
The aim of the present study was to determine whether sunflower meal (SFM), a
highly rumen degradable protein (RDP) source, can be substituted with non-protein nitrogen
(NPN, urea) without impacting negatively on intake, ...