P07401: EPA Water Disinfection Project

Target Specifications

Target Specifications

The chart below correlates specific needs that are satisfied through a engineering specification being met. The importance, units, and a marginal and ideal values for the specifications are also shown. The marginal and ideal values have been set through team discussions with the team and faculty advisors and customer. The definition of each metric is explained in detail below.
Metric # Need #'s Metric Imp. Units Marginal Value Ideal Value
1 1.6, 1.6a, 1.6b, 1.6c Cost per unit to manufacture 9 $ 60 25
2 1.1, 1.1a '# of parts imported 9 # 5 0
3 1.1, 1.1a % of total cost for imported parts 9 % 30 0
4 1.2, 1.1, 1.1a Local fabrication possible 9 % of component type 80 100
5 1.3, 1.4, 1.5 Use of chlorine, wood as fuel source, electricity 3 y/n n n
6 2.1, 2.2, 2.5, 3.1 Total coliform reduction 9 log 4 5
7 2.1, 2.2, 2.5, 3.1 Change in temperature between ambient & fluid in pasteurization section 9 delta deg. C. 40 40+
8 2.1, 2.2, 2.5, 3.1 Reached Safety Zone* 9 y/n y y
9 1.7, 2.1, 2.3, 3.1 Handle sediments 3 y/n n y
10 1.7, 4.1, 4.2 Output before unexpected failure** 9 L 7300 36500
11 1.7, 4.1, 4.2 Average time for preventive maintenance 1 min 1.5 3
12 2.4 Leak proof 1 y/n y y
13 1.7 Thermal cycling until failure** 3 # cycles 2000 4000
14 3.1, 3.2, 3.3, 3.4 Average daily potable output for typical Venezuelan climate 3 L/day 20 40
15 4.2 Usability of setup 9 1-7 rating 4.2 5.6+
16 1.7, 4.1 '# of moving parts 3 # 2 0
'*Equivalent safety zone is a reference safety zone curve shifted by an applicable delta deg. C that fits test conditions

'**Due to required completion date of April 6th, testing will not get done

Engineering Metrics Defined

1. Cost per unit to manufactureis the cost to purchase for the end user through mass production. The idea is to reduce the cost as much as possible through an industrial process, government subsidies, NGO support, and corporate partnerships.

2. # of parts imported are the total number of parts of the SPIHX that is not or may not be available in Venezuela.

3. % of total cost for imported parts complements metric 2. This metric was needed to ensure that although # of parts imported may be a few in quantity the cost incurred may be significant.

4. Local fabrication possible addresses the need of being able to mass produce the SPIHX using the fabrication methods and materials that are locally available in Venezuela. This takes into account such necessities as machining tools, raw materials, and skilled labor.

5. Use of chlorine, wood as fuel source, electricity should not be used or required.

6. Total coliform reduction is an indication of whether or not pasteurization has occurred. Coliform is a group of bacteria whose presence is an indication of contamination. Although a measure of each specific bacteria, pathogen, or virus would have been ideal the team had to take into account safety concerns of handling such contaminants as well as the time it would take to measure each one. A coliform count was deemed adequate by Dr. Lodge of RIT's Biology Dept.

7. Change in temperature between ambient and fluid in pasteurization section is one indicator of how well the SPIHX would perform in Venezuela when compared to results obtained from testing in Rochester, NY. Because of a much colder climate and testing conditions in the winter time, the team measures the change in temperature between the ambient and the water within the SPIHX. This delta T would be the same delta T that can be expected in Venezuela. Hence, although pasteurization may not occur in a very cold climate it is expected that the same change in temperature would pasteurize water in a warmer climate with a much higher starting ambient temperature.

8. Reached Safety Zone takes into account that pasteurization is not only a function of temperature but also of time. Although a binary metric (y/n) the team must verify that the flow rates achieved allow enough time to ensure pasteurization as defined by the safety zone curve. More information about the safety zone curve can be found on the home page.

9. Handle sediments is an attempt by the team to prevent sedimentation from entering the SPIHX. Although much of the design was focused on the SPIHX itself the need had to be addressed nonetheless. Filtering out sediments provides better water quality and prevents clogging of the SPIHX.

10. Output before unexpected failure is one measure of durability. Using 20 L produced per day as a baseline the team established a durability of at least 1 year (7300 L) to 5 years (36500 L) without having to undergo any major overhaul of the product. However, due to time constraints the test will be performed in the next phase of the project.

11. Average time for preventive maintenance is the amount of time to clean out the filter, check water levels in the buckets, and check for broken glass. Any of these tasks that are to be performed by the end-user are defined as scheduled maintenance.

12. Leak proof ensures that there are no leaks from the top channel of the pasteurizer into the bottom channel. The aluminum pasteurizer was plugged at all orifices except at the inlet and outlet. It was then pressurized, left overnight, and was checked to see if any trace amounts of water leaked passed the middle plate and exited the outlet.

13. Thermal cycling until failure is a second measure of durability. The test takes into account the worst-case-scenario in which the SPIHX is emptied of water and thermally cycled. Because of the absence of flowing water the SPIHX would encounter higher temperatures than it would during normal operation. Due to the lack of proper testing equipment at RIT and time the test is planned to be performed during the next phase of the project.

14. Average daily potable output for typical Venezuelan climate uses the World Health Organization's minimum quota of clean drinking water per day for a family of 4 to 6 people (20 L/day).

15. Usability of setup is a measure of the ease of setup the end user would have to go through. This includes fastening together the support legs and hooking inlet/outlet tubing with hose clamps.

16. # of moving parts is a metric introduced in an attempt to minimize the number of moving parts within the SPIHX with the idea that more moving parts leads to a higher probability of failure.