Use of ceramic-based cell immobilization to produce 1,3-propanediol from biodiesel-derived waste glycerol with Klebsiella pneumoniae.

AIMS: The feasibility of the continuous production of a valuable bioplastic raw material, namely 1,3-propanediol (1,3-PDO) from biodiesel by-product glycerol, using immobilized cells was investigated. In addition, the effect of hydraulic retention time (HRT) was also analysed. METHODS AND RESULTS: Ceramic balls and ceramic rings were used for the immobilization of a locally isolated strain; Klebsiella pneumoniae (GenBank no. 27F HM063413). HRT of 1 h is the best one in terms of volumetric production rate (g 1,3-PDO l(-1) h(-1)). The results indicated that ceramic-based cell immobilization achieved a 2-fold higher production rate (10 g 1,3-PDO l(-1) h(-1)) in comparison with suspended cell system (4·9 g 1,3-PDO l(-1) h(-1)). CONCLUSIONS: Continuous cultures with immobilized cells revealed that 1,3-PDO production was more effective and more stable than suspended culture systems. Furthermore, cell immobilization had also obvious benefits especially for resistance of the production for extreme conditions (high organic loading rates, cell washouts). The results were important for understanding the significance of continuous immobilization process among other well-known 1,3-PDO fermentation processes. SIGNIFICANCE AND IMPACT OF THE STUDY: This work is a promising process for further studies, as the immobilized micro-organism was able to reach high volumetric production rates at short HRT, it has an important role in tolerating and converting glycerol during fermentation. Therefore, HRT is a very significant operational parameter (P value <0·05) directly affecting the bioreactor performance and production rate.

Comparative evaluation of the nutrient and COD removal performances of various sequentially operated biofilm reactors.

In this paper, the performances of Fixed Bed (FXB), Fluidized Bed (FLB), and Hybrid (HYB, i.e. fluidized bed followed by fixed) operational conditions of biofilm reactors were investigated. The COD (chemical oxygen demand), TN (total nitrogen) and TP (total phosphorus) were taken as performance-indicator parameters. For that purpose, a pilot experimental setup allowing FXB, FLB and HYB operations in a single reactor was run under varying COD (between 500 to 2000 mg COD l(-1)), TN (between 25 to 100 mg l(-1)) and TP (between 5 to 20 mg l(-1)) influent concentrations. The system was operated as sequentially batch (SBR) and a filtering process was added at the end of each operational phase in order to achieve liquid-solid separation. Results indicated that FXB and FLB are two upper and lower cases, and HYB plays a role between them and respond as a best alternative. For example, for the lower influent concentrations (around 500 mg l(-1)), 84% of COD was removed to final averages of 78 +/- 15.4 mg l(-1); simultaneously, TN reduced to 18.55 +/- 3.48 mg l(-1) (corresponding to 31% TN removal) and 60% of TP was treated to final averages of 1.92 +/- 0.2 mg l(-1) in the HYB operation. When the influent concentrations were increased to 1000 mg l(-1) , COD removal efficiency of the HYB reactor was reduced to 73% (COD reduced from 1005.3 +/- 6.13 mg l(-1) to 270.57 +/- 13.18 mg l(-1)) and, due to incomplete organic matter degradation and oxygen deficiency, 40% of TN was removed to final averages of 34.03 +/- 5.04 mg l(-1) and 56% of TP treated to final averages of 3.98 +/- 0.28 mg l(-1). Performance of the HYB reactor was decreased when influent concentration increased to 2000 mg COD l(-1).

Comparison of various advanced oxidation processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent.

In this paper, a comparison of various advanced oxidation processes (O3, O3/UV, H2O2/UV, O3/H2O2/UV, Fe2+/H2O2) and chemical treatment methods using Al2(SO4)3.18H2O, FeCl3 and FeSO4 for the chemical oxygen demand (COD) and color removal from a polyester and acetate fiber dyeing effluent is undertaken. Advanced oxidation processes (AOPs) showed a superior performance compared to conventional chemical treatment, which maximum achievable color and COD removal for the textile effluent used in this study was 50% and 60%, respectively. Although O3/H2O2/UV combination among other AOPs methods studied in this paper was found to give the best result (99% removal for COD and 96% removal for color), use of Fe2+/H2O2 seems to show a satisfactory COD and color removal performance and to be economically more viable choice for the acetate and polyester fiber dyeing effluent on the basis of 90% removal.

Effect of process configuration and substrate complexity on the performance of anaerobic processes.

The roles of substrate complexity (molecular size of the substrate) and process configuration in anaerobic wastewater treatment were investigated to determine optimal methanogenic technology parameters. Five substrates (glucose, propionate, butyrate, ethanol, and lactate) plus a mixed waste (60% carbohydrate, 34% protein, and 6% lipids) were studied under five reactor configurations: batch-fed single-stage continuous stirred tank reactor (CSTR), continuously fed single-stage CSTR, two-phase CSTR, two-stage CSTR, and single-stage upflow anaerobic sludge blanket (UASB). The substrate feed concentration was 20,000 mg/L as COD. The solids retention time (SRT) and hydraulic retention time (HRT) in the CSTR reactors were 20 d, while HRT in the UASB was 2 d. All reactors were operated for at least 60 d (equal to 3SRT). Substrate complexity was observed to be less significant under two-phase, two-stage and UASB reactor configurations. Two-phase CSTR, two-stage CSTR, and single-stage UASB configurations yielded the lowest effluent chemical oxygen demands (130-550, 60-700, and 50-250 mg/L, respectively). The highest effluent chemical oxygen demands were detected when feeding glucose, propionate, and lactate to continuously fed single-stage CSTRs (10, 400, 9900, and 4700 mg/L COD, respectively) and to batch-fed single-stage CSTRs (11, 200, 2500, and 2700 mg/L COD, respectively). Ironically, the one stage CSTR--most commonly utilized in the field--was the worst possible reactor configuration.