Many thanks to my opponent for this debate. I will dive right in!
Bottled water is a net good for society
Resolution: this resolution is understood to mean that the benefits of bottled water (BW) - as it stands today - outweigh its harms - as compared to available and practical alternatives.
These are outlined as follows:
Producing BW requires the energy of between 32-54m barrels of oil/33 Bn l (2007) . With current production of 390bn l, and assuming doubled efficiency since then, this is 160-260mbl of oil per year. 2000x that of tap water.
This causes environmental harms from oil and gas extraction for PET/PP to make bottles; and contributes to Climate Change. There is an Air pollution component from Burning PET too- with carcinogenic VOCs released into the air from the 12% of plastic burned in the US  and worse in developing nations where most waste is burnt.
Much PET/PP plastic waste from BW ends up in marine environments with the US and China recycling only 30%  of bottles. Only a small fraction is recycled into bottles with most being downcycled into textiles .
It can impair oceanic oxygenation; due to its effect on algae, phytoplankton and zooplankton, and accumulate in the food chain. Given the vast quantities of these plastics in the environment, there is significant risk of profound harm due to BW waste.
BW can come from locations of severe drought - water scarcity in California specifically is exacerbated by BE produced there.
Impact on sanitation:
The best solution for unsafe water is municipal purification that provides safe water without major impact. The reliance on and normalization of BW erodes expectations that such utilities can or will be able to provide clean water . This lack of expectation reduces pressure on governments to invest. Thus BW stands in the way of safe drinking water for all.
Source of Potable water:
BW has the benefit of being a source of potable water, its benefit can be calculated:
China uses 10.4bn gallons of BW; with estimated deaths attributed to water pollution of 60k . With a population of 1.44bn, and 185 gallons per person/year, this works out as water for ~54m people - at the above rate; this works out as 2.6k lives saved. India (1bn gallons, 1.3bn people, 200k deaths ), the total saved is 7.5k.
Or in other words, two countries that make up more than 1/3th of the worlds population, at the very best ~10k lives are saved by BW.
In much of the world, tap water quality is similar to that of BW. While bottled water is most convenient for emergency preparedness, or temporary water issues; other storage methods, water filtration, purification, and water boiling are viable and affordable 
Water purification and filtration be used in preference to bottled water around the globe. Their availability means that there is an available alternative to BW. On China, at 4yuan ($0.6)per litre for bottled water, many filtering options are comparable affordable. Given such an available alternative, the benefits above can be fully realized by other options.
Overall this means that the benefit is primarily an issue of convenience rather than necessity.
Inaction on climate change in 2020 is estimated to be $5Tn per year; $210bn from natural disasters last year alone - not counting indirect economic harm. Air pollution from fossils fuels and manufacturing kills 10m per year, with climate change linked to 5m deaths and displacing 55m. Using the low estimate of 160m barrels equivalent - 0.45% of global usage - the calculable impact is $26bn dollars, 75k deaths, and 225k displaced persons.
We can add to this intangible risks of existential ecological damage to the marine environment; exacerbating droughts, and preventing clean water for all.
This must be weighed against the positive aspects of BW, which as shown is at best that bottled water simply provides convenience.
Lives ended or displaced, massive ecological damage, and critical implications of bottled water above most be put ahead of issues of simple convenience:
Thus one must conclude that bottled water is a net harm to society.