| 1. |
- Bengtsson, Simon, et al.
(författare)
-
Acidogenic fermentation of industrial wastewaters: Effects of chemostat retention time and pH on volatile fatty acids production
- 2008
-
Ingår i: Biochemical Engineering Journal. - : Elsevier BV. - 1369-703X. ; 40:3, s. 492-499
-
Tidskriftsartikel (refereegranskat)abstract
- Acidogenic fermentation of wastewater can serve as a first step in a process for mixed culture production of polyhydroxyalkanoates (PHA) since the produced volatile fatty acids (VFA) are preferred substrates for PHA production. Acidogenic fermentation of industrial wastewaters (cheese whey permeate and three pulp and paper mill effluents) was evaluated in batch and continuous experiments. From the batch experiments, it was found that for whey and one of the paper mill effluents nearly 100% of the soluble COD was readily fermentable. In continuous chemostat experiments with these two effluents, varying the retention time (RT) and pH of the reactors exhibited significant impact on the amount and composition of VFA produced. Increasing RT resulted in increased degrees of acidification up to a maximum of 0.93 g COD of VFA per g influent SCOD at RT 95 h for whey and 0.75 gCOD/gCOD at RT 24 h for the paper mill effluent. Main fermentation products were acetate, propionate and butyrate. Acetate production was rather insensitive to RT while above RT 10 h a shift from butyrate production to propionate production with increasing RT occurred for both effluents. Increasing pH from 5 to 6 resulted in increased amount of propionate. Based on these findings the possibility of regulating PHA monomer composition and associated polymer properties by controlling RT and pH during acidogenic pretreatment was discussed. (c) 2008 Elsevier B.V. All rights reserved.
|
|
| 2. |
- Bengtsson, Simon, et al.
(författare)
-
Production of polyhydroxyalkanoates by activated sludge treating a paper mill wastewater
- 2008
-
Ingår i: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 99:3, s. 509-516
-
Tidskriftsartikel (refereegranskat)abstract
- Production of polyhydroxyalkanoates (PHAs) in activated sludge treating wastewater represents an economical and environmental promising alternative to pure culture fermentations. A process for production of PHA from a paper mill wastewater was examined at laboratory scale. The three stage process examined consisted of acidogenic fermentation to convert wastewater organic matter to volatile fatty acids (VFAs), an activated sludge system operating under feast/famine conditions to enrich for PHA producing organisms and accumulation of PHA in batch experiments. After fermentation of the wastewater, 74% of the soluble COD was present as VFA (acetate, propionate, butyrate and valerate) and the resulting PHA after batch accumulation consisted of 31-47 mol% hydroxybutyrate and 5369 mol% hydroxyvalerate. The maximum PHA content achieved was 48% of the sludge dry weight and the three stage process exhibited a potential to produce 0.11 kg of PHA per kg of influent COD treated. (c) 2007 Elsevier Ltd. All rights reserved.
|
|
| 3. |
- Bengtsson, Simon, et al.
(författare)
-
Production of polyhydroxyalkanoates by glycogen accumulating organisms treating a paper mill wastewater.
- 2008
-
Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 58:2, s. 323-330
-
Tidskriftsartikel (refereegranskat)abstract
- A process for production of polyhydroxyalkanoates (PHA) by activated sludge treating a paper mill wastewater was investigated. The applied strategy was to select for glycogen accumulating organisms (GAOs) by alternating anaerobic/aerobic conditions. Acidogenic fermentation was used as pretreatment to convert various organic compounds to volatile fatty acids which are preferable substrates for PHA production. Enrichment resulted in a culture dominated by GAOs related to Defluviicoccus vanus (56%) and Candidatus Competibacter phosphatis (22%). Optimization of PHA accumulation by the enriched GAO culture was performed through batch experiments. Accumulation of PHA under anaerobic conditions was limited by the intracellular glycogen stored. Under aerobic conditions significant glycogen production (to 25% of sludge dry weight) was observed alongside PHA accumulation (to 22% of sludge dry weight). By applying a subsequent anaerobic period after an initial aerobic, the produced glycogen could be utilized for further PHA accumulation and by this strategy PHA content was increased to 42% of sludge dry weight. The PHA yield over the entire process was 0.10 kg per kg of influent COD treated which is similar to what has been achieved with a process applying feast/famine enrichment strategy with the same wastewater.
|
|
