DESIGN OF BHANDEWADI TO KORADI EFFLUENT TRANSMISSION PIPELINE

INTRODUCTION

Bhandewadi is existing sewage treatment plant at Nagpur owned and maintained by NMC. Presently it is working with inflow of 70 MLD. It has an installed capacity of 100 MLD. It is designed for secondary treatment and effluent is disposed in nearby natural drain after due chlorination. NMC has now proposed to use this effluent for meeting the requirement of Mahagenco for its cooling water. NMC and Mahagenco have entered into agreement for such an arrangement. Installing the pumping system at Bhandewadi, laying the pipeline from STP to Mahagenco is a combined venture of both NMC and Mahagenco.

Requirement of water for Mahagenco is about 130 MLD for their new plant coming up and scheduled to commence functioning in 2014. This plant will be of more modern and using new techniques than the existing one. It will require the cooling system water of improved quality. Presently, Bhandewadi Sewage treatment is not delivering the effluent of that standard. Hence, NMC has planned for two options. In the first option up gradation of the existing facilities at Bhandewadi STP and to install Tertiary treatment facility. In the second option NMC plans to create a new STP for North zone and it will have the capacity another 110+10% MLD.

Mahagenco has total installed capacity of 1100 KW  and under expansion programme they have planned for 3 X 600 KW new plants. These plants will be using new technology and will require improved quality of water fro cooling towers.

Mahagenco has existing power plant and for the cooling system they are bringing water from Pench. The use of water in recent years has shown that demand is about 40 MCUM per annum. It works out to about 110 MLD including the ash washing activity.

Mahagenco wants that the quality refining for the water shall be as near to their plant as possible, so that monitoring would be possible easily. As Mahagenco has decided to utilize the treated waste water from NMC Sewage treatment plant conveying that treated waste water becomes first task and then developing tertiary treatment in the premises of Mahagenco becomes additional task. Final output from the TTP will be equivalent to the requirements of Mahagenco new plants.

For any Sewage treatment plant the flow pattern will be always changing and during the daily variations there will be some peaks and some lean periods and accordingly the output from TTP will be having similar variations. For getting continuous flow output at defined rate it needs to have an equalization tank. Mahagenco wants to take up a full day capacity storage to ensure the reserve as well as daily balancing of flow from the output of TTP.

Chlorination shall be effective in the transit as well as in storage. For adopting standard practice of chlorination Mahagenco will develop and maintain the required facilities and appropriate chlorination will be ensured. Required contact time will be given in the system for effective chlorination. Dose will be dependent on the quality of incoming waste water. Being open containers, complete dissolving of chlorine has to be ensured.

Phased planning

Bhandewadi STP is generating 70 MLD of effluent and it is likely to increase to 110+10% ≤ 130 MLD. Proposed North zone STP with Tertiary treatment facilities will be on way to Mahagenco and will have the similar capacity of 110+10% ≤ 130 MLD.

Initially it is proposed to use the available capacity of Bhandewadi STP and pump the effluent from STP to Mahagenco. For this sump and pump house will have to be constructed at Bhandewadi. The space has been reserved for this activity by NMC.

There will be a proposed TTP on way for North Zone. Rising main from Bhandewadi to Mahagenco will have an incoming and outgoing interconnection to the proposed sump and pump house of TTP. As both the Plants will generate 130 MLD flow in their ultimate stages capacity of rising mains will be 130 MLD. Presently North zone TTP is in the proposed stage direct Rising main from Bhandewadi to Mahagenco will also have the capacity of 130 MLD.

Presently it will start from the Bhandewadi STP and hence pumped treated sewage will be conveyed from Bhandewadi to Koradi. There will be interconnectivity from and to North zone STP so that the same main will be used to pump the North zone treated waste water to Koradi. Both these plants will ensure the total treated sewage flow to Mahagenco of 130 MLD flow. Common rising main will ensure tapping from Bhandewadi flow or North Zone STP (proposed ) Flow.

In the first phase however, Bhandewadi STP effluent will be considered to be conveyed to Mahagenco. As it needs pumping an appropriate capacity pumping station will be developed in the open space available at STP site. Conveyance system will be appropriate rising main from Bhandewadi to Mahagenco via proposed North Zone STP (proposed) site.

Design parameters of Rising Main for phase I

FLow 130 MLD

Bhandewadi G.L.  278.26 m

Mahagenco G.L.   288.15 m

Static head                9.89 m

Length 15131 m

It is proposed to construct a shaft of appropriate height to convert the rising main into gravity main for having smooth operations. A shaft will have a rising main at the center and it will go high to the designed level and effluent will expel into the annular space of the shaft and it will have an outlet at the bottom of the shaft which will lead to the gravity main. Hydraulic level will be balanced as per the flow in the shaft annular space and generate required head for the optimum flow in the gravity main. It will be never more than the rising main top in the shaft and it will ensure the free fall. In any case the pump head will be always constant for any combination of the pumps used. Design of shaft is treated separately. Proposal of shaft will be operative in the initial stages when the pipe line is bypassing the proposed North zone TTP. When TTP will come into existence effluent will be pumped from the sump and pump house at North zone TTP to Mahagenco. In  that case the pipe line will again act as rising main. Static head from North Zone TTP to Mahagenco is more than static head from Bhandewadi to Mahagenco. It is 288.15 – 263.53 = 24.62 m.

The pipe line proposed is rising main. Hence, standard programme of economic diameter of rising main is used to arrive at the competitive size. The programme needs the data to be fed to it in respect of competitive diameters of pipe line of selected materials. M.S. pipe and HDPE pipes are used as the competitive materials. For both the pipes rates as per present market rates have been adopted.

For M.S. pipes, supply rate is further modified to taxes and then to lowering, laying and jointing cost on kg basis. M.S. pipes are required to be protected against rusting, both from inside and outside. Such a treatment for M.S. pipes is normally adopted as Guniting from outside and cement mortar lining from inside. It has its own limitations. It can not be done in the factory and it has to be done at site and it remains on the skill of workers. Further, inside lining can improve the C-value of the pipe line. Cement mortar lining cannot improve C-value beyond 120. With all these considerations it has been proposed to use outside and inside coatings with PE/PU which can be done in the factory and quality lining can be done with minimum thickness 2 mm from outside and 1 mm from inside. C-value can be assured to be more than 140 and the life of coatings is also assured to be more than 30 years. Whole of the pipe line is proposed underground.

Other competitive material for pipe line is HDPE. Approximate diameter required for the flow under consideration is about 1200 mm diameter. Available factories in India are manufacturing HDPE pipes and are supported by relevant ISS. But at present diameters up to 1000 m are supported by ISS. However, for comparison purposes HDPE pipe with 1200 mm diameter have been considered, for which rates have been given By M/S. Jain Pipes. They are manufacturing these pipes as per AWWA standards.

Dia. of pipe in mm	Thickness in mm	Weight in MT Per m	Rate per MT Ex. Factory	Rate with Taxes	Rate per m	Rate including PU coating and lining LLJT per m (6*1.2)
1	2	3	4	5	6	7
1000	10	0.2465	5500	6500	16022	19226
1000	11	0.2711	5500	6500	17624	21149
1100	10	0.2711	5500	6500	17624	21149
1100	11	0.2983	5500	6500	19386	23264
1200	11	0.3254	5500	6500	21149	25379

As far as the diameter is concerned 1200 mm diameter was found to be appropriate with 10 mm thickness. But it is again subject to modification as it has to stand the structural analysis of the pipeline in position. Hence, standard programme was used developed by IWWA for deciding thickness of the pipeline for various criteria. It was found from the output of 1200 mm dia. pipe with 10 mm thickness does not stand to some of the criteria. Output is shown as below,

Above software has been prepared and introduced by Indian Water works Association and has been adopted for a very long period and is trusted by the experienced persons and designers. It has all parameters of design inbuilt. It calculates the structural stability as well minimum thickness of the adopted pipe. Anything inordinate is shown as reflections in red to correct the appropriate parameters. Green displays in the windows will ensure the adopted parameter is satisfactory.

Red figures in the output and also comments in the red indicate to modify the data to suit the requirement. In this case while changing to the thickness from 10 mm to 11mm the output gets modified and is as shown below, 

With 11 mm thickness other structural features are taken care of and a completely safe report output is given. There is no red figure nor there any red comment. Hence, after diameter selection as far flow is concerned thickness is properly selected. Rate table is accordingly changed for 1200 mm diameter 11 mm thickness.

Regarding the C-value for M.S. pipes it normally ranges for 110 for bare pipe and 120 for lined pipes. The lining normally adopted is CM lining. Thickness of lining is normally 12 m to 20 mm. Effective Diameter is net internal diameter. With 12 mm thickness 1200mm diameter will become 1176 mm for calculating flow through velocity.

Instead a new type of lining is proposed in this case. It is called as 3LPE/2LPE External and internal HDPE lining. It can be 3LPU/2LPU lining. In the first case polyethylene is used and in the second case polyurethrene coating /lining is used. Thickness of lining is maximum 2 mm. It serves as a good protection to M.S. pipe line and also it adds to C-value which is maintained always more than 140. Diameter is not much reduced for calculation of flow, and it has a good serving life at par with design period. This being a new technology it can ensure smoothness of surface of the M.S. pipeline at par with nonmetallic plastic pipes. Apart from the strength both in compression and tension and ruggedness, now M.S. pipes can add a feature of smooth flow of liquid, in this case, water. Lining is chemical resistant; hence, for effluent from STP there is full compatibility. The data can be fed in the software for calculating the economic size of rising main.

HDPE pipe is also treated as one of the competitor.

Typical Data for HDPE Resin Grades

		PE 63	PE 80	PE 100
Design stress at 20 degree centigrade	N/sq.mm	5	6.3	8
Density	kg/cum	945-960	945-960	958-960
Melt index (5 kg)	g/10 min	0.4-0.7	0.4-0.7	0.4
Tensile strength at yield	N/ sq.mm	20	20	23
Elongation at break	%	>600	>600	>600
Brittleness temperature	deg. Cent.	<-70 o:p="">

<-70 o:p="">

<-70 o:p="">

Durometer hardness

Shore D

60-65

60-65

60-65

Charpy impact strength

kj/sq.m

No failure

No failure

No failure

Linear expansion

mm/m.deg.c.

0.17

0.17

0.20

Classification of pipe material

Material grade	Minimum required strength in kg/sq.cm at 20 degree centigrade and 50 years of life	Max. allowable stress at 20 degree centigrade in kg/sq.cm	Max. allowable stress at 30 degree centigrade in kg/sq.cm
PE63	63	50	40
PE80	80	63	50
PE100	100	80	63

SDR = D/T. Where SDR is the standard dimension ratio, Do is the outside diameter of the pipe and t is the minimum wall thickness.

For a given pressure rating of the pipe the SDR ratio is constant.

It is now the accepted practice to talk of the pipes with SDR ratio rather than pressure class, such as PN4, PN6 etc.

s = P*Do/(2c + p)

s = minimum wall thickness ,mm P = maximum permissible WP for the given grade of the material kg/sq.cm = WP at 30 Deg cent* DR factor Do = Outside Diameter of pipe in mm c = specified maximum allowable hydrostatic design stress for a given temp. and grade of material kg/sq.cm

Outside diameter of the pipe	1200	mm
Maximum permissible WP at 30 deg. Cent.	6.3	kg/sq.cm
Maximum subjected Temperature	40	deg cent	(underground)
Confrontation to atmosphere time	8760	hr/annum
Expectation of confrontation to particular degree cent during entire design life 30*1/3	10	years
hours in design life	87600
Derating factor at 40 deg.cent.	0.76		Refer to graph
Effective pressure	4.788	kg/sq.cm
c for stress at temp. against design life	4.8	N/sq.mm
	48	kg/sq.cm
s =	57.01	mm

Jain Pipes Ltd. has helped in giving the design of the pipe line. They have selected PE 100 pipe. They have selected the diameter of 1200 mm O.D. pipe. They have given the rate of the pipe in their estimate. The same rate has been adopted in the programme. They have accepted to use the derating

factor as 0.76 for the strength reduction at 40 degree centigrade. SDR is calculated as above. The calculation has been done according to the technical catalogue of Godavari HDPE pipes.

Jain Pipes have given design of pipeline into two parts. For Bhandewadi to North Zone they have proposed PE100 pipes and for the length North zone to Mahagenco they have proposed PE 80 pipes.

This has been corrected and both the stretches of pipe line have been retained as PE100. North zone Plant is not yet in existence but it may come up as TTP in the nearer future. From the sump and Pump house at this TTP effluent will be pumped to Mahagenco. In fact level difference from North zone to Mahagenco is more than that from Bhandewadi to Mahagenco.

Output of the economic size of the rising main is shown below. It indicates that the 1200 mm M.S. Pipe is economical in the design period. It can serve as rising main and as gravity main as required in the different stages of design life of the system.

For ascertaining the most economical diameter of the rising main software has been used which has also been time tested and reliable. It has been developed by the Mahrashtra Jeevan Pradhikaran. Input data is for the prices of various diameters. Flow for immediate stage  and ultimate stages are to be noted. Static head, rate of unit energy, length of main etc. are additional data to be given. Software works out capital costs of the pipe material as well as for energy charges and replacement of pumping machinery etc. and schedules the most economical version of the alternatives from available diameters and selects for preference. As it considers total life of the system of pumping and conveyance the output is more rationalized.

Only drawback of the software is to consider the internal diameter of the pipeline irrespective of pipe material. Hence, additional data for C-value is given to calculate net frictional losses and the thickness parameter and class parameter is converted into the cost for comparison.

On the total considerations the outputs are much reliable and they have been given as below, 

For design of pipe line flow is considered as 130 MLD.

It is also presumed that in the initial stages flow will be slowly rising to 130 MLD. For calculation of the shaft height maximum flow is considered. Shaft will convert the rising main into gravity main. It can be seen that HGL required for taking effluent from Bhandewadi to Mahagenco is 309.23 m to give residual head of 5.34 m. In this case as per claim of HDPE pipes and as per the HDPE lining to M.S. pipes the C-value is taken as 145 instead of 140. It is for the reason that the height of shaft has to be decided and hence maximum C-value is the parameter. For basic design of rising main it has been taken as 140. Residual head can be reduced to 3 m to get the shaft HGL as 307.00 m. Even for this height level difference from G.L. works out to 307.26 – 278.26 = 29 m.

From	To	Length	Total Load	Design Flow	Design Flow	Dia	C-Value	Velocity	Rate of head loss	Head loss	Total Loss
		m	KL	MLD	lps	mm		m/s	m/Km	m	m
SPH	BPT	30	5417	130.008	1504.72	1196	145	1.34	0.946	0.03	0.03
BPT	Koradi	15131	5417	130.008	1504.72	1196	145	1.34	0.946	14.31	15.74

GL at start	GL at end	HGL at start	HGL at end	efft. Head at start	efft. Head at end	static head at start	static head at end	Type of pipe
m	m	m	m	m	m	m	m
278.26	278.26	309.26	309.23	31.00	30.97	31.00	30.97	M.S.
278.26	288.15	309.23	293.49	30.97	5.34	30.97	5.34	M.S.

Getting the flow of 130 MLD will be ultimate stage for Bhandewadi. It will take at least up to 2021 that flow will be generated to this level. Pumping to this high head will not be justified. Hence, it is assumed that maximum direct drawl from Bhandewadi to Mahagenco will be considered as 96 MLD. Pumping machinery can be designed for 96 MLD with a combination of pumps. Selecting 25 MLD pumps 4 working and 2 standby in the initial stages and in the final stages machinery can be designed and replaced as per the demand of situation. Pump bay shall be designed to accommodate 8 pumps out of which only 6 pumps can be installed at present. Head of pumps shall be selected for getting 96 MLD from Bhandewadi in the initial stages. Losses for carrying 96 MLD through 1200 mm dia. Pipeline are calculated as below,

Accordingly , after selection of the pipe material, diameter of the pipe material let the hydraulics decide the economics of the system per a set of period as the time proceeds and how the situation changes with addition of new units of TTP, sump and pump house at North Zone plant and new power plant at Mahagenco.

This design has consideration of the pumping system also.

From	To	Length	Total Load	Design Flow	Design Flow	Dia	C-Value	Velocity	Rate of head loss	Head loss	Total Loss
		m	KL	MLD	lps	mm		m/s	m/Km	m	m
SPH	BPT	30	2920	70.080	811.11	1196	145	0.72	0.301	0.009036	0.00994
BPT	Koradi	15131	2920	70.080	811.11	1196	145	0.72	0.301	4.557413	5.01315

Initially, when effluent from Bhandewadi is to be conveyed to Mahagenco it will have flow ranging from 70 MLD to 80 MLd. It will be convenient to pump the effluent to shaft of about 22 m height by raising HGL to 278.26 m to 300.26 m. Bhandewadi effluent availability will increase to about 96 MLD. And at the most it be about 110 MLD as its rated capacity. Even then the frictional losses will be within limits of HGL 300.26 m to run the effluent by gravity to Mahagenco. As per planning the TTP will expected to come up. Then the situation will change. Bhandewadi sump R.L. of FSL is 278.26 m and its LSL R.L. will be 273.26 m. About 110 to 130 MLD can flow by gravity to TTP sump through same pipe line of 1200 mm dia. as the frictional losses are 1.09 m /km.  Assuming 130 MLD flow for 6.94 km the losses will be (1.09*6.94)*1.1 = 8.32 m. Available head at TTP will be 273.26 - 8.32 = 264.94. and 264.94 – 263 53 = 1 .41 m. Similar calculations for 110 MLD flow show that the available head is (0.699*6.94)*1.1 = 5.34 m, 273.26 – 5.34 = 267.92 m, 267.92 – 263.53 =

4.39 m. For 70 MLD flow the calculations are as below,

GL at start	GL at end	HGL at start	HGL at end	efft. Head at start	efft. Head at end	static head at start	static head at end	Type of pipe
m	m	m	m	m	m	m	m
278.26	278.26	307	306.99	28.74	28.73	28.74	28.73	M.S.
278.26	288.15	306.99	301.98	28.73	13.83	28.73	13.83	M.S.

For 70 MLD flow but with reduced shaft height the calculations are shown as below,

From	To	Length	Total Load	Design Flow	Design Flow	Dia	C-Value	Velocity	Rate of head loss	Head loss	Total Loss
		m	KL	MLD	lps	mm		m/s	m/Km	m	m
SPH	BPT	30	2920	70.080	811.11	1196	145	0.72	0.301	0.009036	0.00994
BPT	Koradi	15131	2920	70.080	811.11	1196	145	0.72	0.301	4.557413	5.01315

GL at start	GL at end	HGL at start	HGL at end	efft. Head at start	efft. Head at end	static head at start	static head at end	Type of pipe
m	m	m	m	m	m	m	m
278.26	278.26	297	296.99	18.74	18.73	18.74	18.73	M.S.
278.26	288.15	296.99	291.98	18.73	3.83	18.73	3.83	M.S.

Bhandewadi STP is at present giving 70 MLD effluent. It is expected to increase to 80 to 85 MLD in the nearer future. However, safe design is considered as flow will increase to 96 MLD for some duration. Pumps used are having a discharge capacity of 21.67 MLD each. With normal flow of 80 to 85 MLD 4 pumps will be in operation. In some higher flow condition 5 th pump may be in operation for small duration. At that time combined flow will be around 96 MLD. Hence, for this flow shaft height is to be checked. It is proposed to keep it at 300.00 m . It is expected that Bhandewadi will be able to give this flow as maximum flow and then for additional demand NZ STP will be developed.

For optimum flow of 96 MLD Shaft level is considered as  R.L.300.00 m

From	To	Length	Total Load	Design Flow	Design Flow	Dia	C-Value	Velocity	Rate of head loss	Head loss	Total Loss
		m	KL	MLD	lps	mm		m/s	m/Km	m	m
SPH	BPT	30	4000	96.000	1111.11	1196	145	0.99	0.539	0.016184	0.0178
BPT	Koradi	15131	4000	96.000	1111.11	1196	145	0.99	0.539	8.16252	8.97877

GL at start	GL at end	HGL at start	HGL at end	efft. Head at start	efft. Head at end	static head at start	static head at end	Type of pipe
m	m	m	m	m	m	m	m
278.26	278.26	300	299.98	21.74	21.72	21.74	21.72	M.S.
278.26	288.15	299.98	291.00	21.72	2.85	21.72	2.85	M.S.

Even with this flow there is a head of 2.85 m at Mahagenco. This is quite safe.

R.L. 300 m has to be taken for calculating optimum head on pumps.

Minimum water level adopted in sump is 274.40 m.

Static head  300.00 – 274.40 = 25.40.

Add for frictional loss and residual head  = 2.60 m

Hence, duty point is 28 m for the pumps.

Total height of the shaft above G.L.  300.00 – 278.26 = 21.74 m.

If there is a flow minimum one pump to be operative to give 21.67 MLD discharge.

Head loss is  0.57 m. Add for residual head of minimum 1 m.

G.L. at Mahagenco is 288.15 m.

Min.HGL required at Bhandewadi Shaft for flow of 21.67 MLD is 288.15 + 1.00 +0.57 = 289.72 m.

Hence, shaft will have LSL of 289.00 m

                                         FSL at 299.00 m

Rising main top             R.L.    300.00 m

Free board                                     2.50 m

Overall height above G.L.   302.50 – 278.26 = 24.24 m

In case of additional flow up to 110 MLD structure will be designed accordingly but rising main can be increased in the shaft when required. At present it will be limited to the pumps proposed to be provided .

Thus shaft will be a container 10 m hydraulic depth and dia. as 12 m.

Volume is equal to 1130 Cum.

Overall size will be dia. 12 m, height of container 13.50 m,

No. of columns  12 + 8 + 1 = 21 No.

Expected bearing capacity is minimum 15 MT/Sq. m.

Preferable bearing capacity 20 MT/Sq.m.

Shaft should have access up to top. Internal RCC staircase to go down to the floor.

Peripherial walkways at LSL and FSL.

Shaft can be open at top.

A protective PU coating shall be given for the water retaining surface with minimum 2LPU 1 mm.

Flow from STP at Bhandewadi will be having a pattern dependent on the consumption pattern of water by the consumers. It will have peaks in the morning and also in the evenings. Flow at the night time will be lesser. Hence, operation of four pumps will be essential according to the flow incoming. It will also be rationalized slightly by providing sump of minimum 2 hours capacity to have partial equalization in the sump itself. For having justified depth in the sump the floor is proposed to be inclined to accommodate lower flows with better pump-able depths. According to flow variations pump numbers can be manually or automatically selected. Pumping head is proposed to be constant up to R.L. 300.00 in the shaft. Further hydraulics after the shaft will be hydraulically auto-decided in the annular space of the shaft to flow water from the pumping station site to Mahagenco.

At Mahagenco also, flow pattern will remain the same. Same fluctuations of flow will be transmitted to Mahagenco and hence, direct utilization of the rated pumping is not advisable. Instead the storage is required for the quantity equalization.

Volume of pipe line from Bhandewadi  to Mahagenco for a length of 15131 m and with 1200 mm dia. is a matter of interest in equalization. 

3.14*1.2*1.2*.25*15131 = 17104.08 cum = 17 ML

Initial stage flow 70 MLD =  2.9 ML/hr average.

Assume peak factor as 3

Maximum rate of flow is 3*2.9 = 8.7 ML/ hour

Hence, volume of pipe line is equivalent to balancing of minimum 2 hours.

Shape of the pipeline from Bhandewadi to Mahagenco is in the saucer shape. It has typical advantages. Line does not get emptyied easily. It remains full up to R.L. 288.63 m. Water level in the shaft also stabilizes in the shaft. In no flow conditions, system  do act as a balancing. When the flow starts water initializes as a jump on the steady surface of the water and energy wave transmits to the far end. When it accumulates in overcoming the frictional losses I the system flow at the far end starts. Being in gravity it is a very smooth transition.