Sustainability Archive » Sludge Handling

Primary Sludge Fermenters in BNR Plants: Are they Cost-Effective for Meeting Effluent Phosphorus Limits?

justin — Fri, 20 May 2011 16:47:06 +0000

The 100 ML/d Pine Creek WWTP is a state-of-the-art BNR facility that serves the City of
Calgary, Alberta. A delay in the construction of the primary sludge fermenters allowed a
comparison of the performance of the BNR process with and without fermentation for
extended periods of time, and facilitated a life-cycle cost analysis in which the cost of
primary sludge fermentation was compared with alternative forms of primary sludge
thickening and meeting the effluent total P limit by chemical addition. Data from the first 20
months of plant operation indicated that, with primary sludge fermentation, the plant is
capable of reliably meeting its stringent effluent total P target of <0.3 mg/L. Without
fermentation, the plant required the in-plant addition for approximately 50 mg/L of alum to
meet this same effluent quality standard. The life-cycle cost comparison between primary
sludge fermentation and enhanced biological phosphorus removal (EBPR), and two
alternative forms of primary sludge thickening and chemical P removal, indicated that
primary sludge fermentation is a cost-effective method of reliably meeting a stringent
effluent total P standard. Using a 20-year net present value (NPV) analysis, primary sludge
fermentation was found to be approximately 8 percent cheaper than mechanical primary
sludge thickening and chemical P removal, and 22 percent cheaper than gravity thickening of
primary sludge and chemical P removal.

Biological Solids Reduction in Activated Sludge with an Anaerobic Side-Stream Reactor

justin — Fri, 20 May 2011 16:23:16 +0000

To investigate the mechanism of excess sludge reduction in an activated sludge process (ASP)
that incorporates an anaerobic side-stream bioreactor (ASSR), four systems were operated in the
laboratory: (a) ASP+ASSR (R1); (b) ASP+aerobic digester (R2); (c) ASP+anaerobic digester
(R3); and (d) ASP without solids wastage (R4). The overall sludge yield of ASP+ASSR (R1)
was the lowest among four systems without showing any negative impacts on effluent quality,
The net sludge yield of R1 was 24-57% and 4-49% less than the three other systems in phase I
and phase II, respectively. Accounting of biomass in R1 reveals that ASSR works like a
conventional anaerobic digester but leads to additional sludge reduction in the main aeration
basin. The results from batch digestion tests indicated that both anaerobically and aerobically
digestible sludge degrade in R1. The extracellular polymeric substances (EPS) extraction results
showed that release and degradation of base-extractable EPS, thought to be iron and/or
aluminum bound floc materials, accounts for lower sludge yield in ASP+ASSR. The bacterial
fingerprinting data showed that there was high similarity of microbial composition between the
anaerobic side-stream reactor and the anaerobic digester; however, there were unique microbial
cells in the side-stream tank reactor as well, indicating that some microbial cells were enriched in
anaerobic side-stream bioreactor due to the continuous sludge recirculation via minimal sludge
wasting.

Cannibal solids reduction technique integrated with activated sludge process

caitlin — Wed, 26 May 2010 20:47:28 +0000

Cannibal solids reduction technique integrated with activated sludge process requires lowest construction and operational costs, without generating a carbon footprint substantially larger than other alternatives. Source: WEFTEC Proceedings 2009 Plant Upgrades Optimized by Efficient Whole Plant Evaluations.

3.4 MGD, Conventional Secondary Treatment Facility, Oak Lodge WWTP