DEPARTAMENTO DE ENGENHARIA CIVIL E ARQUITETURA

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1 SCHOOL YEAR 01/013 1 ST EXAM 013/01/16 08h00 DURATION: h00 THEORY QUESTIONS (maximum 45 minutes) 1. In a pumped trunk main system explain why the smallest technically viable diameter may not be the least expensive alternative. (1,5 points). Explain how the selection of the peak factor in a trunk main system affects the volume of the tanks. (1,5 points). 3. The design of a water supply network includes the choice of diameters that meet the maximum velocity constraint and the minimum and maximum pressure criteria. Indicate which other conditions need to be checked and for which flows. (1,5 points). 4. Indicate the máximum and minimum pressure levels in a water supply network. (1,5 points). 5. Draw the plant layout of the wastewater drainage network (separate system) of the agglomeration in the Figure. The flows are to be treated in a single wastewater treatment plant. (1,5 points). 6. In a separate wastewater drainage network explain why each strech has its own design flow.(1,5 points). 7. Indicate the minimum velocity constraint for a separate wastewater drainage network and explain the need for that restriction. (1,5 points). 8. Indicate the main components of a stormwater drainage system. (1,5 points). 1

2 Problem I (4,0 points) Water source EE Lageosa Average water Population Year consumption (inhab.) (l/(inhab.day) Figure 1 The village of Lageosa will be supplied by the tank represented in Figure 1. This tank will receive water from the water source located at elevation 30 m. The trunk main system will start at the water source with a gravity pipe followed by a pumped system. Data regarding the population evolution and average water consumption are presented in the table. Given these conditions determine: a) The design flow for the gravity pipe considering a daily peak factor. (1,5 points) b) Determine the range of the technically viable diameters, indicating which commercial diameters are available. (1,5 points) c) Draw a scheme of the energy line of the system, from the water source to the tank, for two of the technically viable diameters calculated in b). Adjust the location of the pumping station if needed. (1,0 points) Pipes will be built using High Density Poliethylen (HDPE), with a K S =110 m 1/3 s -1 and the following range of commercially available nominal diameters: 63, 80, 90, 110, 15, 140, 160, 00, 50, 315, 400 and 500 mm. Assume that the diameters correspond to internal diameters.

3 Problem II (4,0 points) The stretch A-B from the wastewater drainage system presented in Figure needs to designed. The pipe material to be used will be corrugated Polyvinyl Chlorine (PVC) (K s =85 m 1/3 s -1 ). The upstream main pipe drains a population of 000 inhabitants and there is a branch connected to manhole A that drains wastewater from 00 inhabitants. The upstream pipe as a 00 mm diameter and the depth of this pipe at the entrance of manhole A is of 1,0 m, measured to the top of the pipe. Cx. A Cx. B Figure Assume that: The average water consumption is 150 l/(inhab.day) Peak factor is given by fp 1,5 60 ; Pop The infiltration flow equals 80% of the average flow; 80% of the water supplied goes to the wastewater drainage system; The nominal diameters for PVC are (in mm): 00, 50, 315, 400 e 500 a) Determine the design flow for stretch A-B (1,0 val.); b) Determine the diameter and slope for stretch A-B that minimizes land movement and complies with the Regulation criteria of velocity and flow height (,0 val.); c) Draw the longitudinal profile of the stretch, indicating ground elevation, bottom elevation and depth of the manholes, distance between manholes, distance to the origin, diameter and slope. (1,0 val.) Assume that the nominal diameters correspond to internal diameters and use the Manning- Strickler formula when needed. 3

4 Formula Q K s S R 3 J 1 n 1 sen n Q 6,063 K i 0,6 D 1,6 0,4 n 4

5 EXTRACT FROM DECRETO REGULAMENTAR Nº 3/95, 3 DE AGOSTO REGULAMENTO GERAL DOS SISTEMAS PÚBLICOS E PREDIAIS DE DISTRIBUIÇÃO DE ÁGUA E DE DRENAGEM DE ÁGUAS RESIDUAIS Artigo 133.º Hydraulic and sanitary sizing 1. In the hydraulic and sanitary sizing the folowing rules should be adopted: a) Maximum velocity for peak flow in design year is 3 m/s for domestic sewer networks and 5 m/s for combined and stormwater systems.; b) The minimum velocity in year 0 is 0,6 m/s for domestic sewer networks and 0.9 m/s for combined and separate stormwater systems. c) If the constraints of b) are not met, the slope needs to be changes until the limits set in b) are met for full section flow. d) In combined and separate stormwater systems the flow height for the maximum velocity mentioned in a) should equal the diameter of the pipe.; e) In domestic sewers the flow height should not exceed 0.5 of the diameter for diameters equal or lower thtan 500 mm, and 0.75 for diameters higher than 500 mm.; f) Slope should be between 0.3% and15%; g) Slopes lower than 0.3% can be accepted as long as the leveling of the pipe, stability and transport capacity are guarateed. h) When there is the need to install pipes with a slope higher than 15% special devices to secure the pipes should be ensured. 5

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DEPARTAMENTO DE ENGENHARIA CIVIL E ARQUITETURA

DEPARTAMENTO DE ENGENHARIA CIVIL E ARQUITETURA SCHOOL YEAR 01/013 1 ST EXAM 013/0/04 15h00 DURATION: h00 THEORY QUESTIONS (maximum 45 minutes) 1. Describe two methods to calculate population projections in a project of sanitary engineering. (1,5 val).