Exergy saving and exergy production in municipal wastewater ...

More documents

Recommendations

Info

Pegah Piri TRITA-LWR Degree Project 12:14 Table 5 Material used in the solution of supply to anode part in the first step of the experiment. material amount Distilled water NH 4HCO 3 KH 2PO 4 MgSO 4 NaCl Na 2MoO4 CaCl 2 MnSo 4 FeCl 2 Yeast 250 ml 0,05 gr 0,9 gr 0,025 gr 0,0025 gr 0,0025 gr 0,0025 gr 0,00375 gr 0,000695 gr 0,5 gr glucose 1,25 gr Glucose concentration in the anode compartment: (1,25 g)/(250 ml) = 5000 mg/l . 5 g/l ÷ 180 g/ (mol glucose) = 27.8 ×10 -3 (mol)/l glucose. 27.8 ×10 -3 (mol)/l glucose ×6 mole O 2 = 1/6 mole O 2/l solution. 1/6×32 = 5.3 g O 2/l = 5333mg/l COD. The anode solution after a period of 5 weeks has the COD value of 650 mg/l. Comparing the COD value 5333 mg/l at the beginning and 650 mg/l at the end the COD removal in the anaerobic situation in the anode compartment has been about 4653 mg/l (about 88% removal). After 5 weeks the solution were renewed in the anode compartment (Fig. 11, 12). The cathode solution made from a 10 mM solution of permanganate ((0.395) g in 250 ml distilled water). The salt bridge were prepared by adding agar to hot distilled water (100gr/l). This solution was saturated with salt (NaCl) and poured in to the tube and left for one night to get dried. The pH was measured for cathode and anode prior to running the cell (Table 6). The higher difference between the pH in anode and cathode solutions makes the proton transfer easier and it can be one criterion to improve electron production in the process. However, there is a limit for this difference. All the spaces between the compartments where sealed using hot glue which could be removed from the device for the next step of the experiment. A resistance of 560 was put in the circuit with the anode and cathode and the device left in the lab for 5 weeks. After 5 weeks the solution in the cathode part became almost colorless. That is because the KMnO 4 had turned into MnO 2 according to the following equation: MnO 4 -+4H + +3e - →MnO 2+2H 2O (70) There were gas bulbs in the anode part after 5 weeks. The solution was renewed in the anode part meanwhile a layer of gloomy biofilm could be seen on the anode electrode. The device left for one night before the amperage and voltage measurement process. Table 6 pH value in anolyte and catolyte solution prior to start of the experiment. anode 5.87 cathode 7.32 34
Exergy saving and exergy production in municipal wastewater treatment Table 7 energy values of two types of food products according to the data written on their package. Energy content juice carbohydrate other 0 146 kJ/34 kcal per 100 ml 8.4 g Energy content milk Arla 3.5% Fat 3 g =51 kJ Carbohydrate 5 g =85 kJ Protein 3.3 g =122.1 kJ There were gas bulbs in the anode part after 5 weeks. The solution was renewed in the anode part meanwhile a layer of gloomy biofilm could be seen on the anode electrode. The device left for one night before the amperage and voltage measurement process. 2.1. COD measurements of food products In this part of the experiment the COD content of the type of juice and milk (3.5% fat) were measured using cuvette tests (HACH DR/2010 Spectrophotometer). The energy values of juice as well as the milk stated on the packages (Table 7) were compared with the measured values of COD content. 3. RESULTS AND DISCUSSION The microbial fuel cell left for 5 weeks to get the biofilm and after this time it re-runned again. The following graphs are the products of the measurement of the amperage and the voltage over the resistance in the circuit. According to the following calculations about 3.846 mA/m 2 could be produced from this microbial fuel cell. The average amperage produced from the microbial fuel cell is 3 microampere (Fig.11) which can be evaluated as following: 1.3 × 6 = 7.8 cm 2 =7.8×10 -4 m 2 (71) (3 μA) / (7.8 ×10 -4 m 2 )=3.846 mA/m 2 (72) This amount of the electricity production is equal to 4653 mg/l COD removal during the experiment. Fig. 11. Amperage produced from the microbial fuel cell. 35
Page 1 and 2: EXERGY SAVINGS AND EXERGY PRODUCTIO
Page 3 and 4: Exergy saving and exergy production
Page 41: Exergy saving and exergy production
Page 47: Exergy saving and exergy production

Exergy saving and exergy production in municipal wastewater ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?