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Feasibility Report Group 1 Scheme Design 2014


Feasibility Report A feasibility study was carried out to investigate which wastewater treatment system was the most cost effective. There were two systems chosen for the feasibility study. The two systems consisted of primary and secondary settlement combined with biological treatment. Screening was used for both systems as a preliminary treatment. Both systems consisted of a balancing tank to control the wastewater flow coming into the system and a sludge collection tank to collect the sludge produced from the system. The flow diagrams for each system can be seen in figure 1 and 2. The two systems were relatively the same except for the primary treatment and the secondary treatment. The primary treatment for option 1 consisted of a horizontal flow settlement tank. The primary treatment for the second option consisted of a septic tank. The secondary treatment for both options consisted of a horizontal flow settling tank, however the second option had an additional component. The additional component for option 2 contained a constructed wetland to treat the effluent coming out of the horizontal flow tank. The biological treatment for each system consisted of an aeration tank. The feasibility study is designed so that the user can define the type of system he/she is going to design. The information required for this stage involves the types of treatment and other specific components e.g. sludge holding tank. Once the information on the different levels of treatment has been input into the spread sheet the next step is to input the relative information that will affect the overall cost of the system. This information includes the cost, size, efficiency, time of construction and life span. The operational costs are also entered into the spread sheet. Some of the operational costs include the electricity, maintenance, cleaning etc. After the cost information has been filled, the information for the plant criteria is input into the spread sheet. This information includes the efficiency required, area of proposed wastewater treatment plant, lifespan and proposed income.

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The final step of the feasibility is to include relative information on the plant criteria. Some of the information for the plant criteria includes the BOD effluent flowing in and out of the system, area of site, proposed income etc. The feasibility spread sheet is designed to carry out a cost benefit analysis using the information input by the user. Once the values were input into the feasibility study, the feasibility study showed that the most cost effective system for Keadue was option 1. The results plotted showed that the initial capital costs for option 2 was a €3000 less than option 1, however the payback period for option 1 over a number of years was significantly less than the second option, showing that option 1 was far more cost effective. Wastewater Treatment System Option 1 Storm Water Overflow

Sludge Return

Collection Network

Screening

Flow Monitoring (Flume)

Balancing Tank

Primary Settlement (Horizontal Flow Tank)

Biological Zone (Aeration Tank)

Secondary Settlement (Horizontal Flow Secondary Tank)

Receiving Water

Sludge Return

Sludge Holding Tank

Figure 1 – Wastewater Treatment Option 1 Flow diagram

Wastewater Treatment System Option 2 Storm Water Overflow

Sludge Return

Collection Network

Screening

Flow Monitoring (Flume)

Balancing Tank

Primary Settlement (Septic Tank)

Biological Zone (Aeration Tank)

Secondary Settlement (Horizontal Flow Secondary Tank)

Constructed Wetlands

Receiving Water

Sludge Return

Sludge Holding Tank

Figure 2 – Wastewater Treatment Option 2 Flow diagram

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Feasibility Report