We conducted a study on a model drinking water distribution system to evaluate the impact of nutrient in the form of sodium acetate on the growth and survival of coliform and heterotrophic plate count (HPC) bacteria f...We conducted a study on a model drinking water distribution system to evaluate the impact of nutrient in the form of sodium acetate on the growth and survival of coliform and heterotrophic plate count (HPC) bacteria for a maximum of 21 days residence time of water in pipes. Our results show that, besides the nutrient added and the absence of any additional source of contamination and additional supply of nutrient, there was significant growth of the above mentioned bacteria in the pipes and bottles for a couple of days, after which the bacterial population began to decrease. The results indicate that the bacteria used the nutrient to grow and multiply until the nutrient was totally consumed and became depleted in the bulk water phase, after which the bacterial population reached a near stationary level and subsequently declined. This suggests the death of some of the bacteria and their dead cells were used by other bacteria for growth and survival. Using a detection limit of 3.3 CFU/100 mL for the coliforms, the study shows that after sometime, no bacteria were found in the water phase of the pipe, however, the biofilm in the pipes still harbored some of the bacteria. The results have revealed that the bacteria also have the tendency to move from the water phase to the biofilm since the latter provides a more suitable environment for bacteria to thrive on and grow, thus prolonging their survival in the system.展开更多
The provenance of sandstones derived from theLower Voltaian Kwahu-Morago Group and the Middle Voltaian Oti-Pendjari Group of the Neoproterozoic Voltaian basin are discriminated by their Sm-Nd Isotopic compositions. Pl...The provenance of sandstones derived from theLower Voltaian Kwahu-Morago Group and the Middle Voltaian Oti-Pendjari Group of the Neoproterozoic Voltaian basin are discriminated by their Sm-Nd Isotopic compositions. Plots from the Sm-Nd data suggested provenance of the Kwahu-Morago Group to be from the Birimian metasediments and associated “basin type”granitoids. The Sm-Nd studies have further revealed an average TDM model age of whole rock samples in the Kwahu-Morago Group to be 2.2 Ga which shows that this portion of the Voltaian Supergroup represents eroded remnants of “basin type” granitoids. Sm-Nd data from the Oti-Pendjari Group suggested provenance from the Birimian volcanic rocks and probably with contribution from the Pan African rocks. Its average TDM model age of whole rock samples was 2.0 Ga, which generally falls in the range of the model ages for the basement Birimian volcanic rocks as well as the model ages for the granitoid rocks and thus suggests the major source rock of the Oti-Pendjari Group as coming from the volcanic belts. The model ages for both groups seem to indicate clastic supply from an early Proterozoic crustal provenance. This study shows that whole rock isotopic analyses can also be complementary in providing an insight into the origin and development of sedimentary successions.展开更多
文摘We conducted a study on a model drinking water distribution system to evaluate the impact of nutrient in the form of sodium acetate on the growth and survival of coliform and heterotrophic plate count (HPC) bacteria for a maximum of 21 days residence time of water in pipes. Our results show that, besides the nutrient added and the absence of any additional source of contamination and additional supply of nutrient, there was significant growth of the above mentioned bacteria in the pipes and bottles for a couple of days, after which the bacterial population began to decrease. The results indicate that the bacteria used the nutrient to grow and multiply until the nutrient was totally consumed and became depleted in the bulk water phase, after which the bacterial population reached a near stationary level and subsequently declined. This suggests the death of some of the bacteria and their dead cells were used by other bacteria for growth and survival. Using a detection limit of 3.3 CFU/100 mL for the coliforms, the study shows that after sometime, no bacteria were found in the water phase of the pipe, however, the biofilm in the pipes still harbored some of the bacteria. The results have revealed that the bacteria also have the tendency to move from the water phase to the biofilm since the latter provides a more suitable environment for bacteria to thrive on and grow, thus prolonging their survival in the system.
文摘The provenance of sandstones derived from theLower Voltaian Kwahu-Morago Group and the Middle Voltaian Oti-Pendjari Group of the Neoproterozoic Voltaian basin are discriminated by their Sm-Nd Isotopic compositions. Plots from the Sm-Nd data suggested provenance of the Kwahu-Morago Group to be from the Birimian metasediments and associated “basin type”granitoids. The Sm-Nd studies have further revealed an average TDM model age of whole rock samples in the Kwahu-Morago Group to be 2.2 Ga which shows that this portion of the Voltaian Supergroup represents eroded remnants of “basin type” granitoids. Sm-Nd data from the Oti-Pendjari Group suggested provenance from the Birimian volcanic rocks and probably with contribution from the Pan African rocks. Its average TDM model age of whole rock samples was 2.0 Ga, which generally falls in the range of the model ages for the basement Birimian volcanic rocks as well as the model ages for the granitoid rocks and thus suggests the major source rock of the Oti-Pendjari Group as coming from the volcanic belts. The model ages for both groups seem to indicate clastic supply from an early Proterozoic crustal provenance. This study shows that whole rock isotopic analyses can also be complementary in providing an insight into the origin and development of sedimentary successions.
