Sustainability Archive » Sustainable Technologies

Molecular Based Characterization of the Microbial Ecology and Activity of Anammox Bioreactors

justin — Tue, 06 Jul 2010 18:35:01 +0000

Stable N-removal and successful enrichment of anammox bacteria was achieved over a period of one year in continuous flow granular sludge bioreactor. C. Brocadia was the dominant anammox community in the reactor, likely by virtue of operating conditions including not maintaining excessive control over nitrite concentrations and the possible influx and utilization of volatile fatty acids in the influent centrate. In general, granulation led to a significant improvement in reactor stability and N-removal performance and was paralleled by a significant increase in bacteria related to the Bacteroidetes/Chlorobi phylum. Based on data obtained to date, expression of both hzo and ISR appear to be suitable biomarkers of anammox activity and have potential as predictive tools for anammox monitoring and control. Source: WEFTEC 2009 Proceedings

Process Consideration to Achieve Nitrogen Removal in a Moving-Bed Biofilm Reactor

justin — Tue, 06 Jul 2010 18:34:28 +0000

The MBBR process is a relatively new biological attached growth treatment system for denitrification. The results of this research should improve the understanding and quantification of the important kinetic and stoichiometric parameters of the MBBR system. The following conclusions can be drawn from overall test results:
i. Biomass density test indicated an increase in biomass density with decrease in temperature. Observed values ranged widely from 6 – 22 g/m2 for R1 and 5-17 g/m2 for R2 throughout the test period (January through June, 2008) for temperatures ranging from 11oC to 24oC.
ii. SDNR was estimated between 1.3 to 2.0 g N/m2/d expressed in terms of total biofilm carrier area. The SDNR expressed as g/m2.d had very little relationship with temperature suggesting a resilience of the overall process to temperature changes. The SDNR expressed as g-NOx- N/g biomass-d was observed to decrease with decreasing temperature. This suggested an Arrhenius relationship, and the Arrhenius constant was calculated as 1.09 for R1 and 1.07 for R2 for a temperature range of 11 – 18 oC, similar to those observed for the activated sludge process using methanol as a substrate. The biomass accumulation at colder temperatures may have contributed to temperature-stable SDNRs when expressed as g/m2.d. This is of practical significance for use of MBBRs in colder climates.
iii. Stoichiometric COD/N ratio was observed in the range of 4.6 mg COD/mg NO3-N to 5.3 mg COD/mg NO3-N and 4.4 mg/mg to 6.1 mg/mg for R1 and R2 respectively. This range is similar to the range observed for denitrification in suspended growth processes.
iv. A model was developed to predict half saturation constant for the MBBR biofilm. The model was based on the non-linear Monod kinetic model and operated on a Microsoft Excel Platform. The model predicted a similar range of KsNOx-N between 0.6 and 2.6 mg N/L for R1 and R2. These values seemed insensitive to changes in temperature with a weak relationship with biomass density. Source: WEFTEC 2009 Proceedings

Low Flow Design of Package Membrane Bioreactor Systems for Total Nitrogen Removal

justin — Tue, 06 Jul 2010 18:31:33 +0000

Valued qualities such as portability, small footprint, fast start up, and high effluent quality have made package membrane bioreactor (MBR) systems a preferred technology for decentralized wastewater treatment applications. Package MBR systems have many advantages which make them ideal for decentralized wastewater treatment applications, particularly those looking for high effluent quality including total nitrogen removal. However, the selection of a package MBR system can be overwhelming for decision makers given the wide variety in available package MBR systems today and if not evaluated properly can lead to selection of a system that cannot meet the low flow challenges often encountered by decentralized wastewater treatment applications. Therefore it becomes important for decision makers to recognize whether the package MBR system is designed with features that allow it to maintain treatment conditions during low flows. This includes a properly designed flow equalization system capable of handling low influent flows which can be done using multiple pumps with VFDs or an influent flow splitter configuration. The package MBR system should also be designed with system turndown through the use of multiple treatment trains and/or use of multiple pumps and blowers. Lastly the package MBR system must be able to maintain control of oxygen delivery during low flows. Selecting a system which incorporates these low flow design methods into the design of the package MBR system will lead to selection of a system that will reliable meet total nitrogen limits at low flow conditions. Source: WEFTEC 2009 Proceedings