Nutrient Removal with Sequencing Batch Reactors¶
Process Control¶
An introduction to automated process control is available in pages 1681 to 1703 of (Metcalf & Eddy, Tchobanoglous et al. 2003).
Sensors¶
Sensors that are can be used to monitor the status of the sequencing batch reactor include pressure, temperature, dissolved oxygen, pH, and turbidity. The pressure sensors are quite versatile and can be used to measure airflow, water flow, volume of water in the reactor, as well as head loss through the course bubble diffuser.
Measure Oxygen Uptake¶
One of the objectives of a wastewater treatment plant is to reduce the Biochemical Oxygen Demand (BOD). The minimum national standard for secondary wastewater treatment is that the average 30-day concentration of \(BOD_5\) be less than 30 mg/L. Biochemical oxygen demand is difficult to measure since it takes 5 days for a test. The long test period also precludes the possibility of using BOD as a control parameter in operating a WWTP. Most WWTPs don’t have the luxury of knowing the concentration of influent BOD. For the NRP the composition and properties of the synthetic feed are known. Thus it should be possible to estimate the BOD removal and the residual BOD by measuring the oxygen uptake rate. Temporarily increasing the oxygen concentration in the sequencing batch reactor, turning the airflow off, and then measuring the decrease in oxygen concentration with time can measure the oxygen uptake rate. The aeration rate with the airflow turned off is insignificant and thus the rate of oxygen consumption is equal to the rate of change of the oxygen concentration.
References¶
Cicek, N., J. P. Franco, et al. (1998). “Using a Membrane bioreactor to reclaim wastewater.” Journal American Water Works Association 90(11): 105-113. Metcalf & Eddy, I., G. Tchobanoglous, et al. (2003). Wastewater Engineering: Treatment and Reuse. New York, McGraw Hill. Rittmann, B. E. and P. L. McCarty (2001). Environmental Biotechnology: Principles and Applications. New York, McGraw Hill. R. Mikler, W. Kramer, O. Doblhoff - Dier, K. Bayer (04/07/95) Strategies For Optimal Dissolved Oxygen (Do) Control https://doi.org/10.1016/B978-0-08-042377-7.50059-3
Lab Setup¶
For 6 weeks of operation of 4 plants prepare 20 L of 100x organic stock. Mix in a 20 L Jerrican and use a power mixer inserted through the opening to mix after the addition of each chemical. Store 100x stock in a refrigerator.
| Compound | Chemical Formula | Molecular Weight (g/mol) | Concentration (mg/L) | total grams required (g) | stock |
|---|---|---|---|---|---|
| Starch | 40,000 | 84.40 | 162.048 | 1 | |
| Casein | 30,000 | 125.00 | 240 | 1 | |
| Sodium acetate | \(C_2H_3O_2Na \cdot 3H_20\) | 136.1 | 31.90 | 61.248 | 1 |
| Capric acid | \(C_{10}H_{20}O_2\) | 172.3 | 11.60 | 22.272 | 1 |
| Ammonium chloride | \(NH_4Cl\) | 53.5 | 75.33 | 144.6336 | 1 |
| Potassium phosphate | \(K_2HPO_4\) | 174.2 | 6.90 | 13.248 | 1 |
| Sodium hydroxide | \({NaOH}\) | 40.0 | 1.75 | 3.36 | 1 |
| Glycerol | \(C_3H_8O_3\) | 92.1 | 12.00 | 23.04 | 1 |
| Magnesium sulfate | \(MgSO_4 \cdot 7H_2O\) | 246.5 | 69.60 | 133.632 | 2 |
| Sodium molybdate | \(NaMoO_4 \cdot 2H_2O\) | 241.9 | 0.15 | 0.288 | 2 |
| Manganese sulfate | \(MnSO_4 \cdot H_2O\) | 169.0 | 0.13 | 0.2496 | 2 |
| Cupric sulfate | \(CuSO_4 \cdot 4H_2O\) | 249.7 | 0.08 | 0.1536 | 2 |
| Zinc sulfate | \(ZnSO_4 \cdot 7H_2O\) | 287.5 | 0.48 | 0.9216 | 3 |
| Calcium chloride | \(CaCl_2 \cdot 2H_2O\) | 147.0 | 22.50 | 43.2 | 3 |
| Iron chloride | \(FeCl_3 \cdot 6H_2O\) | 270.3 | 18.33 | 35.1936 | 3 |
| Cobalt chloride | \(CoCl_2 \cdot 6H_2O\) | 237.9 | 0.42 | 0.8064 | 3 |