Aichinger P.,University of Innsbruck |
Aichinger P.,Alpnter for Climate Change Adaptation |
Wadhawan T.,Dynamita SARL |
Kuprian M.,University of Innsbruck |
And 6 more authors.
Water Research | Year: 2015
Making good use of existing water infrastructure by adding organic wastes to anaerobic digesters improves the energy balance of a wastewater treatment plant (WWTP) substantially. This paper explores co-digestion load limits targeting a good trade-off for boosting methane production, and limiting process-drawbacks on nitrogen-return loads, cake-production, solids-viscosity and polymer demand. Bio-methane potential tests using whey as a model co-substrate showed diversification and intensification of the anaerobic digestion process resulting in a synergistical enhancement in sewage sludge methanization. Full-scale case-studies demonstrate organic co-substrate addition of up to 94% of the organic sludge load resulted in tripling of the biogas production. At organic co-substrate addition of up to 25% no significant increase in cake production and only a minor increase in ammonia release of ca. 20% have been observed. Similar impacts were measured at a high-solids digester pilot with up-stream thermal hydrolyses where the organic loading rate was increased by 25% using co-substrate. Dynamic simulations were used to validate the synergistic impact of co-substrate addition on sludge methanization, and an increase in hydrolysis rate from 1.5 d-1 to 2.5 d-1 was identified for simulating measured gas production rate. This study demonstrates co-digestion for maximizing synergy as a step towards energy efficiency and ultimately towards carbon neutrality. © 2015 Elsevier Ltd. Source
Nogaj T.,University of Central Florida |
Randall A.,University of Central Florida |
Jimenez J.,Brown and Caldwell |
Takacs I.,Dynamita SARL |
And 4 more authors.
Water Science and Technology | Year: 2015
This study describes the development of a modified activated sludge model No.1 framework to describe the organic substrate transformation in the high-rate activated sludge (HRAS) process. New process mechanisms for dual soluble substrate utilization, production of extracellular polymeric substances (EPS), absorption of soluble substrate (storage), and adsorption of colloidal substrate were included in the modified model. Data from two HRAS pilot plants were investigated to calibrate and to validate the proposed model for HRAS systems. A subdivision of readily biodegradable soluble substrate into a slow and fast fraction were included to allow accurate description of effluent soluble chemical oxygen demand (COD) in HRAS versus longer solids retention time (SRT) systems. The modified model incorporates production of EPS and storage polymers as part of the aerobic growth transformation process on the soluble substrate and transformation processes for flocculation of colloidal COD to particulate COD. The adsorbed organics are then converted through hydrolysis to the slowly biodegradable soluble fraction. Two soluble substrate models were evaluated during this study, i.e., the dual substrate and the diauxic models. Both models used two state variables for biodegradable soluble substrate (SBf and SBs) and a single biomass population. The A-stage pilot typically removed 63% of the soluble substrate (SB) at an SRT <0.13 d and 79% at SRT of 0.23 d. In comparison, the dual substrate model predicted 58% removal at the lower SRT and 78% at the higher SRT, with the diauxic model predicting 32% and 70% removals, respectively. Overall, the dual substrate model provided better results than the diauxic model and therefore it was adopted during this study. The dual substrate model successfully described the higher effluent soluble COD observed in the HRAS systems due to the partial removal of SBs, which is almost completely removed in higher SRT systems. © IWA Publishing 2015. Source
Wett B.,ARAconsult |
Omari A.,AECOM Technology Corporation |
Podmirseg S.M.,University of Innsbruck |
Podmirseg S.M.,AlpS GmbH |
And 10 more authors.
Water Science and Technology | Year: 2013
A three-pronged coordinated research effort was undertaken by cooperating utilities at three different experimental scales investigating bioaugmentation, enrichment and performance of anammox organisms in mainstream treatment. Two major technological components were applied: density-based sludge wasting by a selective cyclone to retain anammox granules and intermittent aeration to repress nitrite oxidizers. This paper evaluates process conditions and operation modes to direct more nitrogen to the resource-saving metabolic route of deammonification. Source
Rahman A.,George Washington University |
Riffat R.,George Washington University |
Okogi S.,DC Water |
Takacs I.,Dynamita SARL |
And 2 more authors.
International Journal of Environmental Research | Year: 2016
The stoichiometric parameter namely “Yield Coefficient” associated with growth of certain organism can be determined by direct measurement and/or calculated indirectly. The focus of this paper was on the anoxic yield of heterotrophic organisms using ethanol as an external carbon source during the denitrification process. In the literature, it was observed that yield coefficients can vary for the same substrate, which can be referred to the relative acclimation to the substrate. The aim of this study was to evaluate the yields determined through various catabolic and anabolic estimations. This paper presents ten different yield coefficient calculation methods under anoxic conditions in a sequencing batch reactor using ethanol as an external substrate. The range of anoxic yield using different calculation methods was between 0.423±0.014 to 0.512±0.021 mgCOD/mgCOD at 20°C. It was concluded that there was no statistically significant difference between the yield values calculated from the different methods. Depending of what parameters can be measured correctly for a particular experiment or setup, a particular method can be selected using those parameters to calculate the yield. © 2016, University of Tehran. All Rights reserved. Source
Mancell-Egala W.A.S.K.,University of Virginia |
Mancell-Egala W.A.S.K.,District of Columbia Water and Sewer Authority |
Kinnear D.J.,HDR |
Jones K.L.,Howard University |
And 3 more authors.
Water Research | Year: 2016
Flocculent settling (stokesian) is predominant within ideally operating clarifiers, and the shift to 'slower' hindered settling (non-stokesian) causes both failure and poor effluent quality. Therefore, a new metric for settling characteristics was developed and classified as Limit of Stokesian Settling (LOSS). The technique consisted of determining the total suspended solids (TSS) concentration at which mixed liquor settling characteristics transition from stokesian to non-stokesian settling. An image analytical technique was developed with the aid of MATLAB® to identify this transition. The MATLAB tool analyzed RGB images from video, and identified the presence of an interface by a dramatic shift in the Red indices. LOSS data for Secondary activated-sludge systems were analyzed for a period of 60 days at the Blue Plains Advanced Wastewater Treatment Plant. LOSS for secondary systems typically occurred between 600 and 700 mg TSS/L but reached 1000 mg TSS/L for a good settling secondary sludge and 500 mg TSS/L for a poor settling secondary sludge, settling quality was based on hindered settling rates. In addition, LOSS was collected for granular systems seeded with cyclone underflow from Strass Wastewater Treatment Plant, it was observed that LOSS was higher for granular systems ranging from 1600 to 5500 mg TSS/L for low and high levels of granulation, respectively. The monovalent to divalent cation ratio (M/D) was increased with the addition of sodium ions to deteriorate settling properties. Samples adjusted with higher M/D consistently had 100 mg TSS/L (15%) decrease in LOSS from the control. LOSS numbers collected experimentally were validated with the Takacs et al. (1991) settling model. When compared to flux curves with small changes in sludge matrix, LOSS was proven to be faster at characterizing hindered settling velocity and was less erratic. This is the first time a measurement method has been developed to characterize the transition from stokesian to non-stokesian settling. Additionally, this is the first step in developing new metrics to predict clarifier failure, and determine effluent quality through the development of flocculent settling metrics. © 2015 Elsevier Ltd. Source