A hypothesis within this report is proven correct concerning a correlation between higher mineral levels in bottled water than in tap water in London. The data is presented in many tables in the attached document, these tables are presenting constituent minerals, water hardness’s in 16 bottled water samples and London tap water, molarities of specific samples and minerals. Measurements of elements in tap water in various locations in London were undertaken via the use of a mass spectrometer. An analysis of a sample of Highlands Spring Water proves that the labelling on spring water can be highly inaccurate. Bottled water is also generally much softer than London tap water aside from a couple of anomalous results, these are mentioned later on in the report briefly in more detail. A brief summary upon the reasoning for the increased sodium and potassium levels in central London tap-water samples are addressed, generally explaining in a bit of detail the results of over-abstraction, resulting in salt encroachment and the surface pollution effects on the water table.
An industry worth more than £1.1 billion (1), the bottled water industry profits from commercially selling mineral-rich water claiming that drinking water with more minerals in, is significantly better for our health. Despite the exception of fluoride, which is added to assist dental health across the UK, tap water is certainly lacking in minerals in comparison. Of course, part of this is due to the lifespans of plumbing without treating the water, as certain minerals can precipitate out in underground pipes, creating blockages and strain on the system, but also because in excess, many of these minerals can damage our health.
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Many companies have started to sell mineral water as facial sprays. Of these, a large amount of them are only made up of mineral water under the guise that the minerals contained are anti-ageing, energizing, soothing, antioxidizing among other claims. An example of this is MAC’s mineralized charged water spray, made up almost entirely of water with a few other minerals such as calcium, carbon and a hint of perfume. This product currently costs £190 per litre.(3)
In regards to earlier information in part 1 of this report, it is easily seen that the majority of the commercially bottled waters examined are soft to moderately hard in composition. Water 6 however, produced by San Pellegrino, is very hard in composition. Please refer to figure 2 in order to see the hardness’s of the 16 bottled water samples.
Different hardness’ of water taste different and some hardness is preferred for taste generally, but harder water is more difficult to lather and creates scale, furring up kettle, pipes and more. Water can be permanently hard as a result of a ‘high concentration of anions’ (4) and also the involvement of sulphate and chlorine salts. However, unlike temporary hardness, permanent hardness cannot be remedied by boiling the water thus forcing the offending salts to precipitate.
It is not true to say that all bottled water isn’t as heavily monitored as tap water and Harrogate’s mineral water proves this, quoting on their website (6) that their ‘onsite microbiology laboratory constantly monitors production to maintain the highest possible quality’. The company prides itself upon the purity of their water, explaining the lack of nitrates. However, bottled mineral water contains many dissolved minerals even if it is marketed as pure water. Sometimes minerals are added artificially in order to meet labelling standards and regulations to qualify their water as mineral water, thus falsely promoting that the water is pure and natural(7).
Within this report, the hypothesis shall be either proved or disproved (in the section methodology for the ways in which this has been done).
The hypothesis for this report is the following:
Commercially bottled water contains a much higher abundance of dissolved minerals than in London tap water due to the intense treatment of the latter solution.
In order to compare and contrast the mineral content of bottled water and London tap water, 16 bottled water labels were tabulated in Microsoft excel; each sample bottle was numbered 1 to 16. In order to fill out values for coca-colas Smart water, the internet was consulted. At first, these were written as mg/l just as on the bottles. Later, in a table underneath, in order to see the molarity (mol/l), these values were written out again and re-calculated in order to show the composition of the waters in a different light and in terms of mass. The advantages of this is that the figures are easy to gather, but on the other hand, they may not be fully accurate and are rounded up. Also, on some bottles, the mass of solids in solution was shown. The minerals on the bottle did not add up to this and therefore trace minerals were missing. Therefore, it is not a fully accurate mineral composition of the water.
Please see reference for the full report (9). The average minerals in mg/l that were in common with the minerals of the bottled waters were recorded in a table, figure 4. This allows one to be able to directly compare and contrast the tap water and bottled water in both mineral composition and water quality. The report was a good secondary resource and compiled by Thames Water Utilities Limited. The figures are likely correct and unbiased unlike bottled water figures. This is due to the size, nature and responsibility of the company. The report also dates from 2017 and isn’t as recent as the collected water samples provided by students. Thus a slight error in precision is caused.
Analysis of Other London Tap Water Sources and Highland Spring Water- Mass Spectrometry:
The values within figures 5 and 6 were obtained by means of machinery at University College London. Mass spectrometry is a highly accurate and precise way of measuring mineral content within water samples such as these.
In November, samples in test tubes labelled with dates, names and the content were handed in for analysis. As a handful of samples were gathered from the taps in accommodations across London, this information could be used for the proving of the hypothesis. The analysis of the Highland Spring Water allowed the misinformation on the label to be revealed.
Mass spectrometers split the solutions apart into their individual components and gave information about the solution’s molecular weight. Information regarding the presence of certain elements works by analyzing the sample for specific isotopes. As a result of this, mass spectrometry is wonderful for revealing the identity of an unknown compound but does not work in regards to distinguishing between isomers. Samples can also be contaminated by previous analysis’ by the machine, thus the use of standards and blanks has to be implicated. Standards are materials with very precisely known values are analysed and once these have been analysed, if the analysis is inaccurate, the mass spectrometer can be calibrated to the standard. Blank samples are also baseline non- contaminated samples that can be run through the machine in order to test for any contamination issues or as a baseline before an altered sample is analysed. Mass spectrometry is accurate to 2.7ppm.(10)
Referring to Figure 1, the 16 bottled waters were generally soft to moderately hard with only bottle 6 breaking this mode. Many minerals had a significant presence in the water regardless of the water was still or sparkling. Many bottles were fairly high in sulphates and chloride, indicating a more permanent hardness in many waters. High Mg and Ca content also showed temporary hardness was present in many bottles. Total dissolved solids were not the product of adding the shown minerals on the bottles, hence we can conclude that there are many more trace elements within these waters.
pH’s were present on the labelling on 8 bottles. 5 of these had a pH of 7 and the others were slightly alkaline, at 7.2 (bottle 9), 7.6 (bottle 16) and 7.8 (bottle 13).
68% of the bottled water was soft, 25% was moderately hard and 7% very hard.
68% of the water was dominated by an anionic charge (negative) and the rest cationic (positive).This had no correlation with the hardness of the water however.
Mass Spectrometry results and London tap water-
The most prominent minerals in the Highland Spring Water analysed were calcium, potassium, lithium, magnesium and sodium. This aligns with the labelling however, not in the correct quantities at all. The large quantity of calcium, at 415.14mg/l and magnesium, at 231.77mg/l show us that this is a very hard water.
On the other hand, the London tap water samples from Camden, central London, have the highest hardness with a large amount of calcium present (averaging around 100mg/l) and a small amount of magnesium. Wimbledon water contains a lesser amount of calcium in the sample analysed but aside from that, there is not much variation between Camden, Wimbledon, Shoreditch and London Bridge tap water.
In Bloomsbury, the magnesium content is very similar to the other central London tap water samples analysed by UCL and the mass spectrometer. There is not a significant variation between sodium levels either. Bloomsbury water samples are slightly lower in Na. Potassium and manganese are seen as components in the tap water samples analysed but not in the Bloomsbury water report.
The differences between central London and the suburbs is evident when you see the tap water report for Sutton, 10.5 miles south from central London. There is much less calcium at 82.28mg/l and a reduction in the levels of potassium, sodium and manganese.
London tap water sources are highly treated before distribution to houses. As shown by figures 4 and 5 in the spreadsheet and outlined in the previous section, tap water in London is moderately hard (has a value over 60mg/l but under 120mg/l when the Mg and Ca contents are added).
Hardness is defined as ‘a measure of the amount of calcium and magnesium salts in water’ (2). The hardness of these solutions can vary from being very soft to very hard. Despite the natural softness of rainwater, any water can become hard, as the hardness of water is dependent on the ions dissolving into solution whilst it percolates through the rock it has infiltrated. Calcium and magnesium rich rocks will create a higher hardness of water. Water is trapped either in underground reservoir rocks, covered by cap rocks such as clay, which is impermeable, or in surface reservoirs. Many reservoirs are man-made and water can increase in hardness depending on the composition of the reservoir.
Figure 6- The Geology of the London Basin, displaying the syncline, chalk aquifer and cap rock structure. (11)
The water to London is supplied by an underground aquifer, the cretaceous chalk, a part of the London basin. The cretaceous chalk is porous (an abundance of pore space) and the pore spaces are interconnected. Consequently, the chalk is very permeable. Chalk is made of calcium carbonate and can be dissolved fairly easily into the water, thus there is a large amount of calcium in the tap water hence a higher hardness (a mean of 99.9mg/l- figure 5). The lack of Mg is easily explained, as chalk lacks magnesium and other felsic type minerals.
The cap rock is of a Paleogene and Neogene ages and made up of impermeable clays. Either side of this synclinal basin, there are two aquifer recharging points, one of which is the Chiltern Hills.
Potassium levels are higher in central London due to pollutants and the use of pesticides and the such, these find their way into the water via runoff.
Na levels also are higher due to a high population creating a higher demand for water. This can be seen in the difference between the sodium levels in Sutton and Camden tap water levels. An explanation of this is that as water is extracted, a cone of depression forms, lowering local water levels in a roughly V-shape. A deeper cone is formed the more stress is put upon the aquifer; a result of the aquifer’s inability to replenish it’s water supplies quickly enough/ faster than the rate of abstraction. A higher population means a higher rate of abstraction is needed. Thus water tries to even out the gradient of depression. By doing this, the process of salt water encroachment can occur, especially near the coast, like the London basin. In areas of less abstraction, away from central London abstraction sites, this doesn’t generally occur. Hence why Sutton has a lower sodium level.
In regards to the bottled water, the water is much less regulated by laws than tap water and so has many more constituent minerals. Pollutants are not as common, compared to central London and the higher level of potassium than in most of the bottled water samples. Most bottled water is abstracted in desolate areas and in the Northern areas of the UK, where the population is much less dense. Thus the potassium mg/l average is 1.33 excluding the anomaly (bottle 3, smart water, which has been artificially added) in the pattern.
As shown in part 1, the bottled water mineral statements generally match up to the rocks that they were extracted from, presented in the piper diagram, question 6. This is shows us that it is preferential to commercial water suppliers, signifying that consumers prefer the taste in terms of supply and demand, to abstract water commercially from further North than London. This is not the case for all water, (as shown from the fact bottle water 7 was abstracted in Devon). It is much more common to have much more mineral-enriched water in commercial bottled water than in London taps and the sources for the balance between not too hard but not too soft yet still mineral enriched waters tend to be abstracted from the Northern areas of the British Isles.
Overall, these findings prove the hypothesis that ‘commercially bottled water contains a much higher abundance of dissolved minerals than in London tap water due to the intense treatment of the latter solution.’ As discussed in the previous section and shown clearly within the tables and results presented, although bottled water is on average much softer than water from central London, bottled water is much more enriched with minerals. Often, bottled water is enriched with more minerals and calcium in order to fulfil labelling requirements for ‘mineral’ water. In this light, it could also be argued that bottled water is just as treated as tap water in London, however, after this, bottled water has more minerals overall inside as a result of a lack of monitoring/regulating the quality (and also opposingly the lack of care for the naturalness) of commercially sold water.
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