The stream shown below has a flow of 28,000 m³/d, and a cross-sectional area of 35 m². The stream is saturated with dissolved oxygen (C* = 10 mg/L) and its BOD concentration is 0.5 mg/L. At point (A) 7 km upstream from the stream's confluence with another much larger river. a food processing industry is continuously discharging 1,500 m³/day of wastewater with an average organic composition of CH₂O (which is 90% degradable). The wastewater has a dissolved oxygen concentration of 2 mg/L. A stream sample taken just before the confluence of stream and river has a BOD, 20°C of 3.0 mg/L (k = 0.24/day for BOD assimilation in the lab). a) Calculate the concentration of the wastewater (in units of mg CH₂O/L) before it is mixed in the river. Relevant constants are given below. b) Determine whether the D.O. level in the stream remains above 5 mg/L between point A and confluence of the stream with the larger river. You may assume the following: i) plug flow ii) instantaneous mixing of stream and wastewater iii) stream and wastewater temperatures are 15°C and the applicable 15°C rate constants are: K= 0.18/day for BOD assimilation in the river k3= 0.01/day for BOD sedimentation in the river = 0.23/day for reaeration k₂ iv) C for the stream = 10.0 mg/L c) If the wastewater D.O. is raised to the saturation value of 10 mg/L what degree of waste treatment (% removal), if any, would be needed to keep the D.O. above 5 mg/L in the stream? Q=28,000 m³/d C=C= 10 mg/l BODL= 0.5 mg/L Stream -7 km Area - 35 m river

A city wishes to discharge wastewater primary effluent to a river which supports a trout. The state requires the city to show that the trout population is protected.  Trout require a minimum of 4 mg/l of dissolved oxygen to survive.  Determine the minimum downstream dissolved oxygen concentration from the following information about the wastewater discharge and river.  Does the minimum dissolved oxygen concentration meet the requirements? Wastewater discharge=0.45m3/s, river flow rate= 8.5 m3/s, river cross-sectional area=19m2, dissolved Oxygen concentration in the wastewater= 0.2mg/l, dissolved oxygen content of the river upstream = 8.1mg/l, saturation dissolved oxygen concentration at 20 C= 9.0 mg/l, BOD concentration in wastewater = 85 mg/l, BOD concentration upstream in the river= 0.2 mg/l, BOD decay constant = 0.2 d-1, and the reaeration constant for the river= 0.4 d-1.

There are currently 420 inhabitants in the small village of Pravino. The population is estimated to increase to 940 in thirty years. The current average peak flow is 1.2 L/s and is expected to increase to 2.14 L/s by 2050. The organic load is approximately 45 g BOD5/capita/day. The community is considering a free surface wetland or a lagoon to treat their wastewater.   1. Use the BOD loading to estimate the maximum surface area (in ha) required for a free surface wetland to serve the community by 2050 and remove BOD to 30 mg O2/L and TSS to 30 mg/L.

The town of Viracocha discharges 17,360 m³/day of treated wastewater into the Pachacamac Creek. The treated wastewater has a BOD5 of 12 mg/L and a BOD decay constant, k, of 0.12/day at 10 °C. Pachacamac Creek has a flow rate of 0.43 m³/s and an ultimate BOD, Lo, of 5 mg/L. The DO of the river is 6.5 mg/L and the DO of the wastewater is 1.0 mg/L. Compute the DO and the initial ultimate BOD, Lo, after mixing. Draw the Mass Balance Diagram.

what is the detention time (days) for a tank 50 ft high and 40 ft diameter and flow of 0.5 MGD? a. 9 days b. 1.25 days c. 0.94 days d. 2.5 days e. 0.24 MGD

The density of water at 4°C is 1000 kg/m3 at atmosphericpressure. The gravity acceleration constant (g) is 9.81 m/s2. Thespecific gravity of an industrial wastewater (SGww) is 1.32. Whatis the specific weight of this wastewater?

An action will release DO and BOD to a large low velocity river at a location where the existing conditions of the river have already been determined. Assess the impacted conditions (as a result of this action) at a location 10,000 m down-river from where the action releases the pollution. River: Q = 2 m³/s, A=1m², T = 15 degC, L = 5 mg/L, DO = DOsat Source1: Q = 0.5 m³/s, T = 25 degC, L = 100 mg/L, DO = 1 mg/L