for prof.goodwill only

Facet 1: Quantifying the Need

Tropical Fish require a very specific type of water, with just the right mineral content. If they do not have this proper balance of chemicals they can become sick or even die. Therefore, having access to water that is as close as possible to having no contaminants is of great importance for people who keep tropical fish. This becomes even more important when your research and livelihood depend on keeping these fish alive, as is the case of our project.

Groundwater can vary greatly in quality depending on where you live. Many places have water that is extremely hard, that is, it has a large number of basic salts and minerals, such as calcium carbonate and magnesium. The groundwater here in the Mesilla Valley is considered “very hard” by the USGS. This means that it has over 200 parts per million of just calcium carbonate.

This hardness not only causes problems with filtering devices, pumps, water lines, water treatment systems, and the overall appearance of the tanks themselves, but it also affects the quality of the water in the tanks, as well as the need to use extra tank chemicals to balance the pH of the water, since calcium carbonate is an extremely basic compound. These chemicals are expensive. When the groundwater is especially hard a large amount of these expensive chemicals need to be used to keep the tanks at their specified properties.

The need for an efficient and simple process for removing these contaminants from water in a timely matter is of great importance to researchers, and tropical fish aficionados. There is also a great need for an efficient and low maintenance process for making usable clean water out of very hard water for anything from cleaning things such as laundry, cars, and dishes to having water suitable for human consumption. Clean water is a necessity.

Facet 2: Problem Definition

Design Objective

To design and implement a system or process to remove Calcium Carbonate and other

contaminants from groundwater for use in tropical fish tanks in the biology department.

Design Constraints

Budget: $500

Time: As soon as feasible

Legal: Will not be able to install system ourselves due to contracts with plumbers.

Personnel: Should be serviceable by qualified or trained technicians.

Material Properties and Availability: Water properties are widely known. Calcium Carbonate properties such as solubility and acidity are also well known. Water treatment systems are widely available.

Manufacturability: Single installation means the system will not need to be repeated, but could.

Design Specification

Chosen solution should be able to remove contaminants from groundwater such as calcium carbonate and magnesium safely and effectively while not creating a harmful environment for the tropical fish. Solution should also be able to be replicated and/or moved to another location so solution should not be permanently fixed to its location.

Design Requirements

1. Design should be easily implementable. It should be able to be installed quickly and without the need for any permanent damage or installation to existing water filtration infrastructure.

2.  Design should have a long time interval between needing services. The design should not need to be serviced frequently as this would get in the way of the research.

3. Design should be readily serviceable. The design should be able to be checked on and have any problems fixed and any consumable materials replaced with ease and haste.

4. Design should have a low long term operating cost. The design should be simple and reliable enough that the only long term costs are consumable materials and minor maintenance.

5. Design should be able to effectively remove contaminants. The design should be capable of reducing or removing the levels of calcium carbonate to acceptable levels.

6. Design should be able to reduce the load on the pre existing filtration system to allow it to function more efficiently. The design should make the entire system, from prefiltered input water to the mechanical and biological filters more efficient and  make the system have a longer life.

7. Design should reduce or eliminate the need for water and mineral balancing chemicals. The design should make the total water in the system be balanced in such a way that the need for pH and mineral balancing chemicals is minimal to none.

Facet 3: Concept Development

Developing a first concept for our design was difficult because we first had to figure out the cause for the corrosion and  buildup of calcium carbonate. This was particularly difficult because when we tested the input water the results were very confusing. Every source of water we tested after the filtration and reverse osmosis system tested with minimal levels of calcium carbonate and proper alkalinity (~7 pH). This meant that the reverse osmosis system was working properly, the input water was within specifications, and thus was not the culprit.

After a few meetings and talks with the client and the clients assistants, we were able to determine the cause of the corrosion and calcium buildup. The standard operating procedures for the aquarium system required reverse osmosis input water to counteract evaporation from the tanks. They also called for a monthly “water change” which consisted of replacing 40% of the water in each tank, staggered over a month so all of the water was not changed at once. In doing this water change process the client and their assistants would use carbon filtered groundwater due to the fact that the reverse osmosis system would consistently get clogged and operate well under its specified output of clean water. This carbon filtered water, while being free of large contaminants and stripped of many bad chemicals such as chlorine and chloramine, it still contained upwards of 200 parts per million of calcium carbonate.

Once we discovered the cause of the corrosion the solution was simple, do not use water that has not been processed by reverse osmosis or distillation for water changes. This, however was not a feat that would be easily achieved due once again to the reverse osmosis system not running at its full capacity. It was at this point that we were finally able to start brainstorming how to make the system perform optimally and within the guides outlined in the standard operating procedure.

Brainstorming

After that integral meeting with the client we immediately starting parsing out possible solutions to the problem. During our team meeting that directly followed the client meeting we starting tossing ideas around about possible ways to meet our goal. After this meeting we all used individual brainstorming until our next meeting.

At our next meeting we had a much more in depth session where we added more ideas into our pool of thoughts, and started to flesh out an optimum solution to the problem at hand. Once we came to the final idea we all then went on our own to think about the best way to implement our solution. In the end our solution was a mixture of ideas we had discussed while brainstorming.

Facet 4: Feasibility

The designs obtained by brainstorming were then tested for economic feasibility, personnel viability, and time constraints among many others. We then weighted each assessment and analysed each concept on a Pugh Matrix.

	1	2	3	4
Cost	+	-	-	+
Personnel Requirement	+	+	-	-
Availability of Materials	+	-	+	+
Speed of Deployment	+	-	+	+
Effect on Infrastructure	+	-	-	+
Ease of Use	+	+	+	-

After analysing the proposed solutions we came to the conclusion that our concept number 1 would be analysed further and eventually chosen as our final design.

Facet 5: Preliminary Design

After our feasibility assessment we were able to narrow our options down to one solution as it was the only solution that would be able to meet all of the goals of the design criteria.

The chosen solution was to install a water softener in line before the reverse osmosis system. This was a strange design that had nearly no supporting documentation for, so research needed to be done to discover the effects of softened water on tropical fish and on the existing water filtration and reverse osmosis system.

By installing a water softener before the reverse osmosis system we can effectively replace 200 parts per million of calcium carbonate with 14 parts per million of sodium or potassium depending on salt choice. This massive reduction in contaminants not only helps to maintain the water chemistry but it also reduces the load on the reverse osmosis system by a large factor. Since the reverse osmosis system can effectively have its membrane become  clogged by the calcium carbonate, replacing the high amount of calcium carbonate with low levels of sodium, via ion exchange water softening, will also increase the filter life of the reverse osmosis system, thus reducing costs of replacing filter elements and osmotic membranes.

The water softener design is also one that needs very little maintenance and even less so as the chosen softener has an automatic timed regeneration cycle to flush the ion exchange resin beads with sodium rich water preparing them to remove more calcium carbonate from the water. The predicted salt usage is also very low for the entire system meaning that it would only need to be refilled once a month. Water softeners are readily available at many local hardware stores as well as online, and the salt can be purchased at any general store. There is also a warning light when the salt in the softener is getting low making it nearly fool-proof and automatic.

Facet 6: Analysis

Engineering Model

Due to the scope and scale of the system, as well as it requiring only a single installation we were unable to create a reasonable engineering model. Due to costs we were also unable to create a full scale prototype. In addition creating a scale model would not work in this situation as the parts needed are full size working appliances, and scale versions are not available.

Analysis and Synthesis

Stage 1. Problem Statement

How do we reduce or completely eliminate calcium carbonate and other mineral contaminants from the ground water for use in the tropical fish aquarium room? How much salt will be needed per month?

Stage 2. Summarize Known Information

The levels of calcium carbonate in the groundwater is 250 parts per million and its pH is 8.4 . The ratio of moles of calcium carbonate removed to moles of sodium added is 17:1. The reverse osmosis system is capable of producing 34 gallons/day with new filters and membranes. The total water capacity of all of the tanks is ~1000 gallons. The maximum evaporation experienced from the tanks is 4.8 gallons/day. The percent of water change required once a month is 40%, so the total water usage is ~18 gallons per day.

Stage 3.  Summarize Desired Information

We need to quantify the capabilities of the pre softened reverse osmosis system and make sure they meet the requirements of the design criteria. We need to make sure the softened water will not adversely affect living conditions for the inhabitants of the tanks, nor cause any problems with the pre existing reverse osmosis system, nor cause issues with the mechanical or biological filtering mechanisms for the tanks systems.

Stage 4.  Assumptions

Based on the published effectiveness of the reverse osmosis system and testing results of the the water at multiple stages in the process it is safe to assume that the reverse osmosis system will remove all measurable amounts of the reduced calcium carbonate and sodium that is introduced in the softening process. We will also assume that the water softener acts near its published efficiency, this is a safe assumption because the softener has been oversized to compensate for any drop in efficiency.

Stage 5.  Schematic and Given Data

Stage 6.  Analysis

240 ppm of CaCO3 = 14 grain per gallon

240 ppm CaCO3 = 6 g CaCO3 per gallon

1 grain of hardness removed = 1 part per million of Na added

Assuming water softener will act as advertised:

Resultant softened water will have 14 ppm of Na and trace amounts of CaCO3

Assuming the “clogging rate” of the CaCO3 is similar to that of Na and all other factors the same

240 ppm / 14 ppm = 17

The R/O system will be able to treat 17 times more water before needed servicing which reduces the cost of filters and reverse osmosis membranes by the same factor of 17

Given that the water usage is 18 gallons per day which is half of the rating for the R/O system

18 gallons per day * 14 grain per gallon hardness = 252 grains per day

= 7560 grains per month

and at a ratio of 15000 grains: 3.5 Lb salt

we get 1.76 Lb Salt per month

which is around $0.44 of salt per month

So long term costs are minimal compared to initial cost of softener and installation

Stage 7.  Review results

The results presented above appear reasonable due to the fact that it was designed for a much higher water usage and since our total water usage is quite low compared to the water softeners typical surroundings, a family home where the usage per month can easily reach 10000 gallons.

Stage 8.  Synthesis

Based on our above analysis of the efficacy of the water softener addition to the water treatment system already in effect we have decided to not make changes to the size of the water softener or any other aspect of our design.

Facet 7: Detailed design

The final design solution for the problem was to take the existing reverse osmosis system coupled with the ultraviolet sanitization filter and add a water softener before the reverse osmosis inlet. This will allow the system to take the heavily hard and calcium rich water and turn it into soft and low sodium content water which will be much easier for the reverse osmosis system to handle, thus increasing its filter life expectancy, which also increases its overall efficiency as well as cutting costs on filter replacement and water treatment chemicals. We believe that out of all of the proposed solutions this is the most cost effective and lowest maintenance solution.

After reviewing our design and analysing its hypothetical performance we have decided to choose a water softener based on the needs of the system, we wanted to find one that was low cost, high efficiency, and easy to use. After looking around through a number of similarly sized and priced water softeners we decided to recommend the Kenmore Extra High Efficiency Water Softener Model No. 42-38350. The main reason why we decided to recommend this specific softener is it was the most efficient in its price range, and it was readily available locally.

The downside of our final design for the system is due to bureaucratic red tape we were unable to do more than recommend the softener. We were unable to implement it due to contracting issues with the plumbing company and the university. We had to leave the task of implementing the solution to the client, who hopefully will be able to get the softener installed and be able to save time and money utilizing our design.