Laboratory experiments were carried out at the Tshwane University of Technology, Faculty of Engineering and the Built Environment, Department of Civil Engineering to determine the optimum operating temperature and airflow rate that improves AE. The airflow rates used were 5 L/min, 10 L/min, 15 L/min, 20 L/min, 25 L/min, and 30 L/min. The airflow rate range was chosen based on the fact that low airflow rate produces low OTR/K
La compared with high airflow rates. The low OTR/K
La will result in a low AE, whereas high OTR/K
La will result in high AE in the biological treatment process. The temperatures used were 15 °C, 17.5 °C, 20 °C, 22.5 °C, 25 °C, 27.5 °C, 30 °C, 32.5, and 35 °C. The temperature range was chosen based on the fact that low temperature result in high viscosity compared with high temperature. The low temperature will result in low AE, whereas high temperature will increase the AE in the biological treatment process. The biological treatment process comprised of the following components: aeration tank, dissolved oxygen (DO) meter and probe, thermostat, air pump, airflow meter, air stone disc bubble diffuser, and a digital wattmeter. The components and the schematic diagram of the biological treatment process are detailed in Table 1 and
Figure 1, respectively.
Table 1Components of the aeration unit
Components
. | Type
. | Remarks
. |
---|
Aeration tank | Circular aeration tank (acrylic material) | 10–15 mm thick acrylic material. Dimensions 570 × 300 mm. Total volume is 40 L. Working volume is 30 L |
Dissolved oxygen meter and probe | Hanna HI98196 multi-parameter water proof meter | Measures DO, pH, and ORP |
Thermostat | Local manufacturer | Controls temperature in the range 0 °C–40 °C |
Air pump | Waterfall Resun LP100 | Can supply air between 0 and 140 L/min |
Airflow meter | MF5712 200 L/min digital gas air nitrogen oxygen mass flow meter | Can measure airflow rate between 0 and 200 L/min |
Air stone disc bubble diffuser | Growneer micro pore bubble diffuser | Diffuser is 20 cm in diameter |
Digital wattmeter | Geewiz (kilowatt) | Measures power between 0 and 3,600 watts |
Components
. | Type
. | Remarks
. |
---|
Aeration tank | Circular aeration tank (acrylic material) | 10–15 mm thick acrylic material. Dimensions 570 × 300 mm. Total volume is 40 L. Working volume is 30 L |
Dissolved oxygen meter and probe | Hanna HI98196 multi-parameter water proof meter | Measures DO, pH, and ORP |
Thermostat | Local manufacturer | Controls temperature in the range 0 °C–40 °C |
Air pump | Waterfall Resun LP100 | Can supply air between 0 and 140 L/min |
Airflow meter | MF5712 200 L/min digital gas air nitrogen oxygen mass flow meter | Can measure airflow rate between 0 and 200 L/min |
Air stone disc bubble diffuser | Growneer micro pore bubble diffuser | Diffuser is 20 cm in diameter |
Digital wattmeter | Geewiz (kilowatt) | Measures power between 0 and 3,600 watts |
Figure 1
Laboratory aeration unit.