Bod Problems 2l2w6i

Problems 1. A 10.0ml sample of sewage mixed with enough water to fill a 300ml bottle has an initial DO of 9.0 mg/L. To help assure an accurate test, it is desirable to have at least a 2.0 mg/L drop in DO during the 5-day run, and the final DO should be at least 2.0 mg/L. For what range of BOD5 would this dilution produce the desired results? 2. A test bottle containing just seeded dilution water has its DO level drop by 1.0 mg/L in a 5day test. A 300-ml BOD bottle filled with 15-ml of wastewater and the rest seeded dilution water (sometimes expressed as a dilution of 1:20) experiences a drop of 7.2 mg/L in the same time period. What would be the 5-day BOD of the waste? 3. The dilution factor for an unseeded mixture of waste and water is 0.030. The DO of the mixture is initially 9.0 mg/L and after 5 days it has dropped to 3.0 mg/L. The reaction rate constant k has been found to be 0.22/day. a. What is the 5-day BOD of the waste? b. What would the ultimate carbonaceous BOD be? c. What would be the remaining O2 demand after 5 days? 4. A waste had an ultimate BOD of 300 mg/L. At 20C, the 5-day BOD was 200 mg/L and the reaction rate constant was 0.22/day. What would the 5-day BOD be of this waste at 25C? 5. Some domestic wastewater has 300mg/L of nitrogen either in the form of organic nitrogen or ammonia. Assuming that very few new cells of bacteria are formed during the nitrification of the waste (that is the O2 demand can be found from a single stoichiometric analysis of the nitrification reactions), find: a. the ultimate nitrogenous O2 demand b. and the ratio of the ultimate NBOD to the concentration of nitrogen in the waste. 6. Suppose some pond water contains 10.0mg/L of some algae, which can be represented by the chemical formula C6H15O6N, using the following formula: C6H15O6N + 6O2  6CO2 + 6H2O + NH3 NH3 + 2O2  NO3- + H+ + H2O a. Find the theoretical carbonaceous oxygen demand b. Find the total theoretical (carbonaceous plus nitrogenous) oxygen demand 7. For a solution containing 200 mg/L glycine, a. Find the theoretical carbonaceous oxygen demand (CBOD) b. Find the ultimate NBOD c. Find the total theoretical BOD 8. A wastewater treatment plant serving a city of 200,000 discharges 1.10 m 3/s of treated effluent having an ultimate BOD of 90.0 mg/L into a stream that has a flow rate of 8.70m3/L and a BOD of its own equal to 6.0 mg/L, the deoxygenation rate constant k d is 0.20/day. a. Assuming complete and instantaneous mixing, estimate the ultimate BOD of the water just downstream from the outfall. b. If the stream has a constant cross- section so that is has a flow at a fixed speed equal to 0.3 m/s, estimate the BOD remain in the stream at a distance 30,000 meters downstream 9. The wastewater has a dissolved oxygen concentration of 2.0-mg/L and discharge rate of 1.1 m3/L. The river that is receiving this waste has DO equal to 8.3 mg/L, a flow rate 8.7 m3/L and temperature of 20C. Assuming complete and instantaneous mixing, estimate the initial dissolved oxygen deficit of the mixture of wastewater and river water just downstream from the discharge point. 10. Just below the point where a continuous discharge of pollution mixes with a river, the BOD is 10.9 ppm and DO is 7.6 ppm. The river and waste mixture has a temperature of 20C, a deoxygenation constant k d of 0.20/day, an average speed of 0.30 m/s and an average depth of 3.0 m. a. Find the time and distance downstream at which the oxygen deficit is a maximum b. Find the minimum value of the DO