Sep 25, 2023
Field sampling for drinking water
- 1Dhulikhel Hospital;
- 2University of California Berkeley
Protocol Citation: Sneha Shrestha, Christopher LeBoa 2023. Field sampling for drinking water. protocols.io https://dx.doi.org/10.17504/protocols.io.ewov1o6bplr2/v1
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: April 27, 2023
Last Modified: September 25, 2023
Protocol Integer ID: 81093
Funders Acknowledgement:
Bill and Melinda Gates Foundation
Grant ID: INV-000572
Abstract
The method we used for sampling drinking water for households when detecting S. Typhi and Paratyphi in Nepal
Guidelines
Sterility during water sample collection
1. Sterility of collected water sample: The primary risk of sample cross-contamination comes
from either the field assistant or water/DNA from another household.
a. Field assistant: It is important that the field assistant, whom comes into contact with
water at multiple households, uses proper technique and does not contaminate the
water being collected by touching or handling the opening or inside of the bag.
b. Collection instrument: while the inside of each WhirlPak is sterile, the outside is not.
Thus, a Whirlpak cannot be directly dipped into a water tank to collect water since it
is not sterile, has been handled by the field assistant and may have come into
contact with another household’s water during transport. Items owned and used by
the household are an exception. Since water at the household level is routinely
transferred via multiple non-sterile methods (pipes, valves, jugs, cups, etc) prior to
consumption, it is ok, for water to be in contact with these devices prior to collection.
2. Contamination of household water: It is similarly important that potential pathogens are not
introduced into a water supply when we collect from there.
Definitions:
- Origination of water: Defined as the principal, original source of water. For water that is processed or distributed (i.e. municipal or private water company) then the initial water treatment and distribution plant is the origination point. For unprocessed water (i.e. collected or distributed directly from ground water or surface water for consumption), then the source of water prior to distribution or collection is the origination (i.e. river or groundwater).
- Freshness: Refers to time since water is delivered from the origination source. For instance, the freshest possible water would be immediately collected from a pipe that has actively running water from a municipal water source. Water that has been stored and has been stagnant/still for an amount of time, freshness decreases. Thus, water collected from a running pipe and stored for 24 hours would be less fresh then running pipe water but fresher then water collected and stored 1 week prior.
- End-user treatment: Any treatment of water done at the household level prior to use or consumption, including but not limited to filtration, boiling or chemical treatment such as chlorination.
Materials
Materials list
1.Gloves
Whirl-Pak bag (Nasco product Number: B01027) or sterile bottle
2.Barcode Labels (blue, printed in duplicate)
3. Bag locking pipe closures (Nasco product number: B01595)
4. Ice packs
5. Insulated bag or cooler box
6. Empty bottle sleeves—plastic bottle with the top cut off (for keeping bags/bottles upright during
transport)
7. 2 sterile water pumps (for difficult to reach water collection)
All water will be collected at the point closest to the origination of that water supply prior to end-
user treatment to minimize the time for S. Typhi or Paratyphi DNA to degrade in
water, if present. If the only option is to sample from water that has been stored, choose the
freshest (most recently stored) source.
Sample Collection
Sample Collection
Pre-label all Whirl-Pak bags with a fill line representing 1 litre of water
a. Fill a bag with exactly 1 litre of water in the lab. Mark the outside of the bag with a
line where the water reaches. Copy this line to the rest of the Whirl-Pak bags.
Place two duplicate random number stickers on the Whirl-Pak bag.
Put on gloves and ipen the bag, taking care not to touch the inside of the bag
Fill the bag with 1 liter or water
If necessary, ask the household member to turn on the water spigot so that you do not contaminate your gloves.
If the household uses water from a communal spigot, collect from this point
i. If a hose is connected to a communal spigot, remove it to collect directly
from the tap
If the community spigot is not functioning/the water is not running, sample water from the house or building collection tank, using the sterile hand pump
If the storage tank in inaccessible, you can sample from stored water in a jug
i. Choose the freshest source of stored water (the one that was stored the most recently) ii.Avoid using a cup or container to transfer water from the jug If the container is too heavy to lift and pour into the Whirl-Pak bag, you can request to use the same cup or device the household uses to transfer water.
Close the bag with the pipe-locking device
Remove gloves
Scan the sample barcode into RedCap
If the code does not scan, manually enter it
Take a picture of the sample in the RedCap app, making sure that you can see the
barcode number
Sample transport
Sample transport
Place the full bag Whirl-Pak in an upright plastic bottle inside the cooler bag/backpack
Unused Whirl-Pak bags should be kept in a separate compartment from water
samples
Minimize opening and closing the cooler to maintain temperature control.
If maintaining temperature control is a challenge, consider placing temperature loggers
inside each cooler bag.