SODIS related
Mindy Weimer - Sunday 21 May 2006
My name is Mindy Weimer, and I am an Environmental Engineer working as a consultant with USAID-Environmental Services Program in Jakarta, Indonesia. I am doing an action research project on point-of-use drinking water treatment alternatives for the urban poor. The alternatives I have introduced to four of the communities I work extensively with are ceramic filtration, chlorination, and SODIS.
I have been monitoring water quality from each of the volunteer-users’ in each of the four communities this month. Aside from water quality results, I am finding different reviews as I gather the users’ feedback. It has been both insightful and inspiring to follow this conference and learn of others experiences doing similar work. Thank you all for sharing.
I would like to share my bench-scale results from one of my SODIS experiments and ask if anyone else has seen similar results. At 6am (28.1degC) the water had 16FC/100mL, at 9am (44.8degC) rose to 56FC/100mL, but by 12pm (59.4degC) was down to 0FC/100mL. I tested again at 6pm (after 12hrs) and 6am (after 24hrs) and FC/100mL remained at 0. However, at 6am the following morning (after 48hrs) the water was 4FC/100mL.
I am also wondering if anyone has or knows of investigations of phthalates from plastic water bottles leaching into the water when exposed to high temperatures and sunlight. I am curious how significant this may be for SODIS users.
I welcome any feedback and wish you all the best in your work. Despite the extra email load, I regret this discussion forum is coming to an end.
You can contact me directly at: mindy.weimer@gmail.com
Replying to Mindy's SODIS QUERY
Kevin McGuigan - Monday 22 May 2006
Mindy can I ask what method you were using to monitor the faecal coliforms, because it might have some bearing on the explanation.
I had a similar experience of apparent reactivation when I was carrying out SODIS evaluation studies in E Africa in the early 90's but in my case the reactivation was artefactual becase I was using agar coated dip slides which I was just dipping into the neck of the bottle. Over time agar nutrients were getting washed off the dip -slides and encouraging growth from bacteria which we think were attached to detritus floating at the top in the neck of the bottle and shielded by the cap.
Once we introduced better sampling techniques I never saw this again so I would be really interested to know the mechanics of how you are monitoring the faecal population. Post exposure reactivation is an area that does require further study.
Nevertheless we changed our protocol to recommend that the SODIS water is consumed as soon as possible after exposure and not left for more than 24 hours before consumption.
Regarding thalates leaching from the plastic, Martin Wegelin & I looked at this previously with water samples in PET bottles that were exposed for varying times between 15 and 126 days. Using 2-step mass spectrometry we were unable to detect any photoproducts (J Water SRT-AQUA 2001;50:125-135). I have just finished a further (and as-yet un-published) study where water was stored in PET bottles and left in direct sunlight in Southern Spain for 1 year. UV/Vis spectroscopy, GC/MS and CHemical Oxygen Demand (COD) measurements all failed to detect any photoproducts.
You can contact me directly at kmcguigan@rcsi.ie if you want to chat about this in more detail.
