GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- VII (New) EXAMINATION — WINTER 2019
--- Content provided by FirstRanker.com ---
Subject Code: 2171306 Date: 03/12/2019
Subject Name: Wastewater Engineering
Time: 10:30 AM TO 01:30 PM Total Marks: 70
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
--- Content provided by FirstRanker.com ---
MARKS
Q.1 (a) Write down operational problems with its solution occurred in aerated grit chamber. 03
(b) A wastewater flow of 0.60 m³/min containing 150 mg/L of oil and grease is to be reduced to a concentration of 25 mg/L. Assuming the following data, design a dissolved air flotation system. 04
--- Content provided by FirstRanker.com ---
Surface loading rate (SLR) = 130 L/m²-min; Wastewater temperature = 35°C; Air solubility at 35°C (S?) = 17.15 ml/L; A/S = 0.025 (mL/mg); Fraction of air saturation (f) = 0.80 and Recycle system pressure = 500 kPa.
(c) Determine the size, dimensions and HRT of a UASB reactor which will be used for the treatment of an industrial effluent. The wastewater is mainly soluble, containing carbohydrate compounds and a granular sludge is expected. Suppose 90% soluble COD removal, 50% of the influent pCOD degraded and 90% of influent sulfate is reduced biologically. Methane production at 35°C = 0.40 L CH4/g COD; Reactor volume effectiveness factor = 85%, density of methane at 30°C =0.6451 g/L and height for gas collection = 2.5 m. Also determine total gas production (assuming 65% methane), energy available from methane and alkalinity requirements. 07
Item Value
Flow Rate 1000 m³/day
COD 2300 mg/L
--- Content provided by FirstRanker.com ---
sCOD 2000 mg/LAlkalinity: 500 mg/L as CaCO3
SO4 200 mg/L
Temperature 30°C
Q.2 (a) Differentiate between domestic wastewater and industrial wastewater. 03
--- Content provided by FirstRanker.com ---
(b) Design a cylindrical flash mixing tank by determining the tank dimensions and required input power using following data: Design flow rate = 11.5 x 106 m³/d, Rapid Mix time= 5 s, Rapid mix G =600 s?¹ and ? = 1.5195 x 10?7 N/m².s. 04
(c) Design a grit chamber having a rectangular cross-section and a proportional weir as the velocity control device, with the following supplied data: 07
Maximum flow = 12 MLD; Maximum temperature = 26°C; Minimum temperature = 15°C; Specific gravity of grit particles = 2.65 and Diameter of smallest grit particles to be removed = 0.02 cm.
OR
(c) Assuming suitable design criteria, compute the dimensions of a rectangular settling tank to remove suspended flocculent particles from the average wastewater flow of 15000 m³/d. A column test indicates that an overflow rate of 40 m/d will produce satisfactory removal of suspended floc at 3.5 m depth. 07
--- Content provided by FirstRanker.com ---
Q.3 (a) Write down operational problems of UASB. 03
(b) Assuming suitable design criteria, design a trickling filter system to treat an average domestic wastewater flow of 10 MLD having influent BOD5 equal to 250 mg/L. The desired effluent BOD5 is 25 mg/L or less. BOD5 = 175 mg/L & to be operated at 25°C. The depth of modular plastic media to be used is 6.0 m & recirculation ratio will be 2:1. The treatability constant determined at 20°C = 0.06 min?¹ & desirable concentration of effluent is 20 mg/L. 04
OR
(c) Write the Eckenfelder equations (with & without recirculation) for Bio tower design. 07
Q.4 (a) Enlist and Explain the operational problems of chemical unit operations. 03
--- Content provided by FirstRanker.com ---
(b) Estimate the size of digester required to treat the sludge from a primary treatment plant designed to treat 38000 m³/d of wastewater. Check the volumetric loading, estimate percent stabilization and the amount of gas produced. For wastewater to be treated, it has been found that the quantity of dry volatile solids and biodegradable COD removed is 0.15 Kg/m³ and 0.14 Kg/m³, respectively. Assume that the sludge contains about 95% moisture and has a specific gravity of 1.02. Assume hydraulic regime of the reactor is complete mix. (SRT =10 days @ 35°C; Efficiency of waste utilization =0.70; Y =0.08 Kg VSS/Kg bCOD utilized; k? = 0.03 d?¹ and digester gas is 65% methane) 04
(c) Explain the factors responsible for bulking of sludge. 07
Q.5 (a) An activated sludge plant is to be designed for 10 MLD domestic wastewater flow to operate at 10 days MCRT and 6 hours of HRT. Assuming BOD5 20°C as 175 mg/L in influent to the aeration tank, sludge wasting flow equal to 70 m³/d and return sludge concentration equal to 8000 mg/L, determine the concentration of MLVSS to be maintained in the aeration tank to achieve effluent BOD5 of 30 mg/L. Also determine the recirculation ratio at which plant should be operated. Assume the kinetic coefficients K?=0.06 d?¹ and Y = 0.6. 03
(b) Explain the phases of SBR operational cycle with neat sketch. 04
OR
--- Content provided by FirstRanker.com ---
(c) Write a short note on extended aeration. 07
Q.5 (a) Explain the working mechanism of “Rotating Biological Contractor with neat sketch. 03
(b) Design a rotating biological contactor to treat 10 MLD flow of municipal wastewater having BOD5 concentration of 250 mg/L. The primary treatment removes 30 % raw BOD5 and desired effluent BOD5 is 250 mg/L. Assume 0.05 m³/m²-d hydraulic loading and other suitable data if needed. 04
(c) Enlist and explain the types of filter presses. 07
Q.6 (a) Explain various methods of dewatering of sludge. 03
--- Content provided by FirstRanker.com ---
(b) Design sludge drying beds to dewater the digested sludge produced from wastewater treatment plant based on the activated sludge process designed for 50000 population. Assume other suitable data. 04
OR
(c) Define the following terms: (i) Sludge volume index, (ii) Mean cell residence time and (iii) Mixed liquor suspended solids 07
Q.6 (a) Explain various methods of thickening of sludge. 03
(b) Write a short note on “Natural evaporation “as a treatment of wastewater. 04
--- Content provided by FirstRanker.com ---
This download link is referred from the post: GTU BE/B.Tech 2019 Winter Question Papers || Gujarat Technological University
--- Content provided by FirstRanker.com ---