Development of a laboratory clarifier test to predict full scale primary clarifier performance

The objective of this research was to develop a laboratory test procedure to predict full-scale primary clarifier performance using Chemically Enhanced primary Treatment [CEPT]. A method was developed that simulated actual primary clarifier performance, with chemical enhancements, based on simulating full-scale surface overflow rate [SOR] and flocculation time in the laboratory. The method used for this test was adapted from a procedure used for sizing of Lamella Separators. Validation of the developed method was done by comparison of laboratory data, with stress test data from two full-scale clarifiers, at the Blue Plains Advanced Wastewater Treatment Plant in Washington, DC, USA. The results indicated that the laboratory SOR test method could be calibrated to predict and optimize full-scale primary clarifier performance

Specific methanogenic activity of halophilic and mixed cultures in saline wastewater

Wastewater containing high concentrations of salt, are difficult to treat using biological treatment processes, especially anaerobic processes. Limited information is available on methanogenic activity in saline environments. The objective of this research was to investigate the activity of halophilic methanogens, digester sludge and a mixed culture of halophilic and methanogenic bacteria, at various levels of salinity, in terms of lag period and specific methanogenic activity [SMA] at two temperatures. For the halophilic bacteria at 35 oC, the initial SMA ranged from 0.46 to 0.90 g acetate/g VSS.d, but decreased at higher salt concentrations. The maximum SMA varied from 1.2 to 2.08 g acetate/g VSS.d. High sodium chloride concentrations had a significant adverse effect on digester sludge. At 25 oC, at salt concentrations of 30 g/l and above, the digester sludge could not acclimate even in 50 days. Little difference was observed in the maximum SMA of mixed culture and halophilic bacteria at high salt concentrations of 40 -50 g/l

Effect of trace metals on halophilic and mixed cultures in anaerobic treatment

Trace metals are known to stimulate the activity of anaerobic methanogenic bacteria involved in the degradation of organic matter. The objective of this research was to investigate the effect of three trace metals, iron, nickel and cobalt on the activity of halophilic methanogens, digester sludge and a mixed culture of halophilic bacteria and digester sludge, at various salt concentrations. Iron slightly stimulated both initial and maximum specific methanogenic activity [SMA] of halophilic methanogens at all salt concentrations. Iron addition was also able to increase both initial and maximum SMA of the mixed culture. Iron could not stimulate either initial or maximum SMA of digester sludge at salt concentrations of more than 10 g/L. Adding cobalt showed no benefit on the initial and maximum SMA of halophilic methanogens. A slight increase in the initial SMA was observed in mixed culture when cobalt was injected to the system containing sodium concentrations of 10-30 g/L. At salt concentrations above 40 g/L, cobalt could stimulate the maximum SMA of mixed culture. No benefits were found when cobalt was added to the digester sludge at sodium concentrations higher than 20 g/L. Nickel was observed to increase the initial SMA of digester sludge at all salt concentrations, and the maximum SMA of mixed culture at salt concentrations of 30-50 g/L.tions of 30-50 g/L