CHAPTER 1

1DR. NURUL ADYANI GHAZALIENVIRONMENTAL ENGINEERING DESIGNDesign of Sewer2Sewage flow rate Defining Dry Weather Flow (KCK), which is an important parameter in the process of sewage treatment.

Calculate KCK and list the factors that affect it.

Defining and calculating principle of Population Equivalent (PE)

Designing sewer3 It is an important factor in the design of a wastewater treatment units..

It affects the size of the sewer, screen size, the size of the sedimentation tank, etc.Sewage flow rate 4Dry weather flow rate (KCK) Dry Weather flow rate is the average sewage flow is calculated based on the total population and daily water consumption per capita.5Some common methods of calculating KCK:

i. The amount of water supplied x population KCK = (q, water consumption) (P, population) = (225 L/capita.day) x (1000 capita) = 225 m3/day

ii. (Amount of water supplied x population) lost

KCK = (i) - (20%~30% lost) = 70 ~ 80% (water supplied x population)Dry weather flow rate 6Dry weather flow rate iii. (Amount of water supplied x population) + other resources - water loss

KCK= (i) + (other sources such as well) (20 ~ 30% loss) 7Calculate the value of KCK to an area of 10 000 people if the rate of water consumption is 250 L/capita.day.

Calculate the value of KCK to an area of 20 000 people if the water consumption rate of 250 L/capita.day and the ratio of sewage/water supplied is 0.67.exercise8PE can be defined as a amount of wastewater contributed by premises such as industrial and commercial premises that state's burden in term of total population.

It influenced the design of a treatment plant..

PE can be defined as the total population contained in Table 2 MS1228: 1991 and Guidelines for Developers Volume 4, 1998.Population equivalent (PE)9Type of PremisesPopulation Equivalent (Recommended)Residential5per houseCommercial: Include offices, shopping complex, entertainment/recreational centres, restaurants, cafeteria, theatres3per 100 m2 gross areaSchools/Educational Institution: - Day schools/institutions0.2per student- Fully residential1per student- Partial residential0.2per non-residential student1per residential studentHospitals4per bedHotels with dining and laundry facilities4per roomFactories, excluding process water0.3per staffMarket (wet type)3per stallMarket (dry type)1per stallPetrol kiosk/Service stations15per stationBus Terminal4per bus bayTaxi Terminal4per taxi bayMosque0.2per personChurch/Temple0.2per personStadium0.2per personSwimming pool/Sports complex0.5per personPublic toilet15per toiletAirport0.2per passenger bay0.3per employeeLaundry10per machinePrison1per personGolf course20per hole10A separated sewer system will be build for a residential area consist of 250 houses. Other building located in the area are: A primary day school (100 students) 500 meter square of shopping complexes A wet market (15 stall) 300 meter square of restaurants

Calculate the value of PE at the residential area.exercise11Sewer are designed based on gravity flow.

It should be designed precisely to convey sewage in size, gradient/slope sufficiently and sufficient velocity.

Determination of the appropriate size is important because it can prevent erosion and sedimentation from occurring.

Sewer is not designed as full (usually ~ full) for the following reasons: - Avoiding the anaerobic sludge when full. - Taking into account the possibility of a sudden increase in flow rate beyond expectations. - Taking into account the infiltration of ground water or surface water excessSewer design approach12main design parametersDesigned in peak flow rate or maximum flow rate

- Sewer was designed at Qmax to ensure that the size of the selected sewer/culvert able to drain sewage in excessively..Peak factor, Fpeak = 4.7 P-0.11

*P = Population Equivalent (PE) in thousands13Designed taking into account the self-cleaning velocity

- The sewer position must be in certain slope so that the velocity of the sewage are at acceptable range.

- In general, the velocity of wastewater in the sewer should be in the range of self-cleaning velocity of the following:

Qminimum, v = 0.6 - 1.0 m/s

Depending on the size of sewer (Table 2.8) Qmaximum, v = 0.8 - 4.0 m/smain design parameters14Qminimum sewage is often taken as the KCK/Fpeak

Qmaximum sewage taken as 4.7P-0.11KCK

Other factors are summarized in Table 2.9.

Using the principle of an open channel. This is because sewer flows by gravity and not flowing full.

Usually used Manning and Chezy methods.main design parameters15manningV = 1/n(R)2/3(S)1/2 Q = AV Q = 1/n(A)(R )2/3(S)1/2 Where;V = velocity of the sewage (m/s) Q = flow rate of wastewater (m3/s) at full flow R = A/P (bounded sewage wet area) A = area of the sewer (m2) P = perimeter (m) D = diameter culvert (m) S = slope of culvert (m/m) n = Manning coefficient of hardness (Table 2.10)16Wet area is the area bounded with water in the sewer. For example, R = A/P is the area A divided by the circumference (perimeter) x.Notes

17Design approachIn the design, we are required to determine the size of the sewer in accordance with the following data:

- Peak discharge of sewage. - The type of sewer with a particular value of n. - The slope of the sewer (s)

- Velocity self-cleaning. - High percent of sewage in the sewer.

18Design stepsDetermining the value of d/D (if the flow is 50% of full, d/D = 0.5).

- Determining the value of q/Qfull and v/Vfull from Design Chart (Figure 2.7) on the selected value of d/D. Let q/Qfull = x and v/Vfull = y.

- From the peak flow rate, q (given the actual flow rate), determine the Qfull and Vfull. So Qfull = q/y and Vfull = v/y.

Value Qfull inserted in the Manning equation.

Then, the actual velocity of the sewage (flow at d/D) was revised in two conditions, in Qmaximum and Qminimum and compared with self-cleaning velocity.19Design an isolated sewer that flows 70% full at maximum flow rate(peak) 0.42 m3/s and minimum flow rate of 0.047 m3/s. Take gradient as 1:600 and type of sewer is cast iron (n = 0.013).EXAMPLEQmax = 0.42 m3/sQmin = 0.047 m3/ss = 1:600n = 0.013

Sewer flows at 70% full20solutionFor this example, we need to know what is the size of sewer and flow data. Due to sewage is not flowing full, the data can not directly enter into the Manning formula because Manning formula only applies for flowing full situations.21Known that the actual design of the sewage velocity, which is the peak velocity corresponding to 0.42 m3/s (ie, flowing at 70% full). But the value of 0.42 should not be put in Manning formula.

Diameter can only be obtained by knowing the value of Q at full flow.

How to get Q in full flow?

The answer to this question is to use the design charts.solution22solutionV = 1/n(R)2/3(S)1/2 Q = 1/n(A)(R )2/3(S)1/2 Sewer flows at 70% full, this can be expressed as d/D = 0.7

where, d = actual depth of the sewage D = diameter sewer23solutionFrom the design charts, at d/D = 0.7, q/Qfull = 0.85 v/Vfull = 1.14

Thus, determination of the diameter of the sewer:

Known Qmax= 0.42 m3/s

Enter the value of Q in Formula Manning

q/Qfull= 0.850.42/Qfull = 0.85

Qfull = 0.494 m3/s

Q = 1/n(A)(R )2/3(S)1/2 24R = A/P at full flow (Manning)solutionR= D/4So 0.494 = (1/0.013)(/4D2)(D/4)2/3(1:600)1/2D8/3

= 0.494/0.9788

D

= 0.77 (sewer size required)

25solutionDetermination sewage velocity and checking,Known,

V = 1/n(R )2/3(S)1/2

= (1/0.013)(0.8/4)2/3(1/600)1/2 = 1.07 m/s (full flow)

Check the actual velocity of the sewage in Qmax and Qmin, to ensure self-cleaning velocity met.

Check v at maximum flow, Known v/Vfull = 1.14 (from chart)

At full flow (at Qmax) V = 1.07 m/s

So, vreal = 1.14 (1.07) = 1.22 m/s (0.8 < v 0.6m/s (v self-cleaning) ~ OK

27A guide to use chartSee d/D on the y axis. See x axis which is represented by v/Vfull and q/Qfull. The numbers on the x-axis applies to both.

i) There are 4 lines on the chart (two straight lines and two dashed lines). Take the dashed line because n that we have is constant (unchanged).

ii) For the above value, see the dotted line for flow rate and velocity.28Extend d/D = 0.7 for both line and projected on the x-axis when it touches the line.

If done properly, the value of d/D = 0.7, v/Vfull = 1.14 and q/Qfull = 0.85.

Note that; q = actual flow rate of sewage (70% full) Q = Manning flow rate (full flow) v = actual velocity of sewage (70% full) V = Manning velocity (full flow).A guide to use chart

30A separated sewer system will be build for a residential area consist 550 houses and other building: A primary day school (100 students) A secondary boarding school (300 students) 600 meter square (m2) of shopping complexes A wet market (25 stall)From the information given, determine the design for a concrete sewer for with 1:100 gradient. The system is design to flow 70% full at peak flowrate. Determine:

Population Equivalent (PE) for the residential area;Peak Flowrate (Qpeak)Diameter of the pipe;Sewage velocity at peak flow (Vmax) and average flow (Vmin).exerciseTHANK YOU

End*07/16/96*##