A

PRESENTATION

ON

COST ANALYSIS OF

ACTIVATED SLUDGE PROCESS

INTRODUCTION

Efficient working of wastewater treatment plant depends upon the accuracy of design of wastewater treatment plant.

Sewage Treatment Plants (STP’s) and Effluent Treatment Plants (ETP’s) essentially work on certain well-established principles.

Economics of construction is a major factor in construction of any wastewater treatment facility

COST ANALYSIS

For the design of waste water treatment plant we need to know: Initial construction cost Annual operation cost Maintenance cost

COST ANALYSIS

While preparing a cost estimate consider the following points:

• Both capital and annual cost be reported • All cost estimates be referenced to some cost

index (as costs are changing so rapidly & also to allow effective cost comparisons to be made in the future)

Engineering News- Record Construction Cost Index

Current value of index Current cost = --------------------------------------- x Cost cited in report. Value of index at time of report

 Projected future value of index

Future cost = --------------------------------------- x Current cost. Current Value of index

Source: U.S Environmental Protection Agency

  

DEVELOPING COST CURVES FOR TANKS

The analysis and structural design of all types of tanks is carried out by using “SEPL- Tank” software.

All the tanks are designed using this single software, hence uniformity in the results is also expected. The outputs given by “SEPL Tank” are then fed into a spreadsheet prepared in

“Microsoft Excel” to work out the quantities.

METHODOLOGY

Selection of Shape and Size

Analyze Circular, Square and Rectangular shaped reactors for their cost.

Identification of all possible sizes of the components

Work out the maximum size of a tank that can constructed for a STP.

Materials and Specifications

METHODOLOGY

The rates used for calculation of the cost of a tank can be taken from Schedule of Rates of respective State PWD.

The rates taken include the following sub heads:

1.     Cost of Materials

2.     Cost of Labor

3.     Nominal Carriage

4.     Contractor’s profit

5.     Over head charges and

6.     Contingencies.

DEVELOPING COST CURVES FOR MECHANICAL EQUIPMENTS

For ASP we consider the cost of following equipments:

• Equalization Basin• Settling Tank and Clarifloculator• Fixed Aerators/ Floating Aerators• Clarifier• Pumps

CIVIL STRUCTURES

Circular Tanks

Square Tanks

Rectangular Tanks

ESTIMATES OF QUANTITIES OF CIRCULAR TANKS

Rates as per Rajasthan Schedule of Rates:

Cement Concrete M 25 = Rs 2,367.00 per m3

P.C.C (1:4:8) = Rs 18.50 per kgSteel (Fe 415) = Rs 910.00 per m3

Shuttering = Rs 73.00 per m2

Excavation = Rs 26.50 per m3

 

CIRCULAR TANKS

Geometry of circular tanks to be considered:• Diameter of tank• Height of tank• Wall thickness• Length of toe• Length of heel• Thickness of toe and heel• Thickness of base lab

Dia of Tank(m)

Depth of Tank(m)

Capacity( m3 )

Total CostRs (lacs)

Cost/Liter

 

2.00 1.70 5.34 0.10 1.90

3.00 2.20 15.55 0.21 1.36

4.00 2.70 33.93 0.34 1.01

5.00 3.20 62.83 0.52 0.83

10.00 3.20 251.33 1.37 0.55

A graph is then plotted between capacity (in cubic meter) and cost (Rs in lacs) and the equation for best-fit curve is obtained.

COST FUNCTIONS FOR CIVIL WORKS

COMPONENT FUNCTION REGRESSION COEFFICIENT

Circular Tanks C=0.0256 V0.7430 0.9962

Square Tanks C=0.0320 V0.7776 0.9863

Rectangular Tanks

Aspect Ratio 1.5

Aspect Ratio 2

C=0.0364 V0.7709

C=0.0339 V0.7998

0.9864

0.9907

C=Cost in Lacs, V=Volume of Reactor in m3

COST FUNCTIONS FOR MECHANICAL EUIPMENTS

COMPONENT FUNCTION REGRESSION

COEFFICIENT

Fixed Aerators C= 0.3512 H 0.6405 0.9073

Floating Aerators C= 0.9718 H 0.4597 0.9433

Clariflocculator Mechanism

C= 0.8213 D 0.7394 0.9769

Clarifier Mechanism C= 0.6274 D 0.7749 0.9547

Clarifier Scraper Arm C= 0.3107 D 0.8098 0.9767

Centrifugal Pumps C= 0.0828 H 0.9794 0.9746C= Cost in Lacs, H= Horse power of equipment, D= Dia of Clarifier in m

CONCLUSIONS

Circular tank is most economical in construction cost.

As Aspect ratio of a Rectangular tank increases its cost also increases.

CONCLUSIONS

Designers should also add local variations like:

Land acquisition rates, development of site, additions for piping and interconnecting paths, drains, lighting and laboratory equipments etc.

Energy requirements for construction costs and for maintenance, labor, parts and supply costs are also reported.

THANK YOU