5. (Phosphorus cycle, Julana Lake has a surface area of 4.1 x 106 m². The 2.02 m³ s¹ and a phosphorus concentration of 0.023 mg L-¹. A wastewater average depth of the lake is 15 m. The lake is fed by a stream having a flow rate of treatment plant discharge into the lake at a rate of 0.2 m³ s¹ and a phosphorus concentration of 1.1 mg L. Runoff from the homes along the bank of the lake adds phosphorus at an average rate of 1.35 g s¹. The settling rate of phosphorus from the lake averages 0.94 year¹. The river flows from the lake at a flow rate of 2.42 m³ s¹. Assume evaporation and precipitation to negate each other. 5.1. What is the concentration of phosphorus in the river flowing from the lake? fabo lake.

Flow rate:  1.5 m3/s Pollution: pesticide permethrin Lake size: 100m x100m x 2.5m Steady state concentration of permethrin leaving the lake is 1.4 ppm Average cross-sectional area of the river is 2.7 m2. Half-life of permethrin in this environment is 19 hrs. What is the concentration of permethrin entering the lake and what distance downstream of the outlet would the concentration be less than 1 ppm?

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.

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