Unfiltered petri dish: We found out that it had fewer number of bacteria colonies,but some of the colonies were much bigger than the others,and the colonies also vary in colour,like white and yellow.For all the filtered petri dishes,there were a lot of small colonies,but there are higher number of colonies, with an average colony count of 120.The colonies might not be bacteria,but wild yeast as they grow rapidly on durian husks. We also found out that pond water contains a huge amount of Escherichia coli (E. coli) and since the fruit itself is antibacterial, its properties have been transferred to the husk.We do not have an electric field gradient,which is used in seeing whether a bacteria is good or bad,therefore we conclude that the filtered water is safe for consumption, as most of the bacteria in it is good.
From our data,we conclude that our engineering goal 'Making a water filter capable of producing clean water' is a failure,as we are supposed to filter water that has no bacteria,and we cannot have it have any bacteria at all,be it good or bad.
Explanation of key findings:
Studies show that the activated charcoal is good at trapping carbon-based impurities ("organic" chemicals), as well as things like chlorine. Many other chemicals that are not attracted to carbon at all (sodium, Nitrates, etc) will just pass right through which creates a filter function while another study shows that durians are common biomass and a potential bioabsorbant for the removal of Cr(VI) in waste water and they can absorb up to a cpacity of 117 mg/g and another study showed that scientist tried to make mouthwash with durains' sugary coating found on the husk as it has antibacterial properties.
Areas of Improvement:
We could improve on the sanitation, as we washed the durian husk and placed the filtering agents into the filter (tube) without washing our hands or placing on rubber gloves and we also could sterilise the filtering agents before using them. We also could improve on our time management by getting the materials earlier.
Entry 1: (13 Jan 2015 - 22 Jan 2015)
We stayed back on these days to washed and dried the durians at the back of the physics lab and used a clean bucket and we repeated these steps until there was no more smell.During these period we faced some difficulties such as when we expected the durians to be odourless and dry but it didn’t turn out as well and repeated the cleaning process again and again.We also checked with Mr Tan on the conditions of the durian and we also brought lemons near the end and sliced them and they dried pretty fast.
Entry 2 :(25 Jan 2015 - Monday)
The proposal was finalised and submitted to Mr Teng in hard copy and we tested if the durians can be expanded when in water as Mr tan thought it was too small.After that,we went to clementi with Mr Tan to buy acrylic tube,plastic glue and acrylic board.We encountered a problem as there were no activated carbon ,so we had to go some place else to buy them.
Entry 3 :(30 Jan,2 & 3 Feb 2015 - Friday ,Monday & Tuesday)
We brought the fine sand and grand to school which are materials that we needed,and sawed the acrylic tube.At first,we wanted to use the full length of the tube,but Mr Tan Said that too long or too short a tube world be bad,so we got down to sawing it into 3 pieces. Because the edge were too jagged,we used sandpaper to smoothen it out.One of the tubes also snapped while cutting,so it took a great deal of effort to smoothen it.
Entry 4 :(5 & 6 Feb 2015 - Thursday & Friday )
We managed to get activated carbon,charcoal and pebbles and bring it to school, and got most of the materials ready to be used for experimenting.
We plan to start the experimentation hopefully on the next week onwards while we cultivate the bacteria so that we can count them as(before filtering) fast as we can.
Entry 5 :(10 & 13 Feb 2015 - Tuesday & Friday )
We measured the amount of different materials to be put into each acrylic tubes by using a plastic cup that we borrowed from other team which was not used and put the things into the tubes.The first is to contain the pebbles,gravel and charcoal while the second is to contain the activated carbon,durian husk ,coarse sand and the fine sand.We then put them into each tubes and found out that we has not given the pump by Mr Tan which we quickly went to ask him for it and filter the pond water and collect them with beaker and plastic containers.We then put them into the agar plates and incubate them.
Entry 6 :(16 Feb-20 Feb 2015 - Monday to Friday)
We stayed back when we could and wanted to do the experiment when we found out that the 2 lemon skins that we has cut and put into the filter which we used last week were rotten which in turn makes us decide to throw them away and stop using it as it caused the result gotten from the agar plates to contain more bacteria than the one unfiltered and the time needed to dry more of them is quite a long time with the rainy days in Singapore.With the friday not being able to go to the lab and do our project as we were supposed to start doing the report, we did our experiment on tuesday and thursday after school and got our result the next day as the time needed to incube the agar plate is 24 hours.Not as bad as on the result we got on friday ,we still have more bacteria present on the agar plate which contain water that is filtered which confuses us and leads us thinking that as the results were open up to the air for 2 days, bacteria might have come to it or has died.
With the friday to do our report and blog.
Entry 7 :(23 Feb - 27 Feb 2015 - Monday to Friday)
On tuesday we decided to use the plastic test tubes to keep the filtered water as it is enclosed which prevents the bacteria to come in and we did the experiment again this time we rinse the tube containing the things needed to filtrate the water first to ensure that they are clean.We then waited till wednesday for the results and found out that the bacteria from the unfiltered pond water is too many to be counted with the filtered one having lesser than the unfiltered one but still uncountable, given the time we decided to use the data result we had previously and to our surprise we found out that durian contain good bacteria itself which allow us to think positively and that the bacteria colonies of the result of the unfiltered pond water with the filtered pond water is different in terms of size and colour with the unfiltered one having larger colonies ,yellowish and white in colour but has less amount of bacteria while the filtered ones has smaller bacteria colonies with only white in colour.We also found that durian highly prevent e coli to grow on it and as e coli is a bacteria that is harmful in water we felt a relief that we are able to think that the result taken from the filtered water contain good bacteria.