Table 1.

Modifications to the bag-mediated filtration system kit

Variable	Version	Modification	Justification
Pre-screen mesh	1	30 × 76 cm (10 L)
	2, 3	Pre-screen mesh	A pre-screen mesh on the collection bag inlet prevented coarse sediment and debris from entering the bag
Collar	1	Detachable brass ring
	2, 3	Stainless steel rolled ring clamp	The stainless steel rolled ring clamp held the pre-screen mesh onto the collection bag inlet The clamp had a side loop for rope attachment The clamp had a second side angled loop that facilitated easy placement of the filled collection bag on the tripod stand
Sample collection bag  Outlet port	1	Quick-disconnect check valve port Located 4 cm above the bag’s bottom
	2	Open ¼-inch barbed tubing adapter port Located 10 cm above the bag’s bottom	Due to clogging in the first-generation bag, a straight barbed tubing adapter replaced the quick-disconnect check valve The catchment area below the outlet valve increased from 4 to 10 cm for capture of settled solids. Settleable solids accumulated below the outlet prior to filtration, thus minimizing solids entering and clogging the filter
	3	Open ¼-inch barbed tubing adapter port Located at the bottom of the bag Heat-sealed 15.5° slope angles toward the outlet	The lower sediment catchment area of the bag was ineffective as settled solids resuspended during the rolling of the bag when pressure was applied, released, and reapplied. Therefore, the catchment area was removed A 15.5° slope was heat sealed onto the bottom of the bag. This enabled bleeding of settled solids to a second vessel prior to filtration of the remaining clarified sample
Sample collection bag  Size	1	30 cm × 76 cm (10 L)
	2	29 cm × 81 cm (10 L)	The bag height increased due to the switch from the detachable brass ring to the stainless steel rolled ring clamp. The top of the bag folds over the metal clamp for attachment, requiring a greater bag height
	3	28 cm × 64 cm (6 L) 28 cm × 94 cm (12 L)	Typically, field technicians processed less than 4-L wastewater or wastewater-impacted surface waters in Nairobi, making collection of a 10-L water sample unnecessary. A 6-L bag enabled bleeding and collection of an initial 1 L settled volume, and filtration of the remaining clarified 5 L A 12-L bag facilitated use of a new protocol (not discussed in this work). The large bag enabled bleeding and collection of an initial 2 L settled volume, and filtration of the remaining clarified 10 L through two filters
Sample collection bag  Color  Volume markings	1	Bright yellow
	2	Drab green with white screen printing Volumetric demarcations: 0.5-L increments	Bright yellow bags attracted attention from on-lookers. Therefore, the color was changed to drab green to reduce attention Volumetric demarcations were added, enabling measurement of the filtered volume
	3	Drab green with white screen printing Volumetric demarcations: 0.25-L increments	The volumetric demarcations were changed to 0.25-L gradations to facilitate easier and more accurate measurement of the filtered volume