Table 3.

Change in DALY per person per day from base case (based on exposure frequency and proportion of population exposed for Adults).

Improvement Option (Refer to Base Case in Table 2, and Detailed of Options Described in S7)	Household Environment	Groundwater	Local Drain	Community Drain	Downstream Waterway	Fresh Produce	Downstream Environment	Total	Explanation of the Results.
1a. Reduce leakage from sewer and drain into groundwater (as 25% population assumed to use groundwater daily for drinking)	0%		0%	0%		0%	0%		A very small change in leakage flows from sewer and drain (2% change) resulted in an overall reduction in health risk, despite a slight increase in risk in relation to downstream waterways
1b. Reduce groundwater use for drinking by half by providing an alternative water supply	0%		0%	0%	0%	0%	0%		The health risk associated with the groundwater pathway was significantly reduced. Groundwater risk reduction by providing an alternative water supply may have a greater positive impact than reducing groundwater pollution (1a).
2. Cover local drains	0%	0%		0%	0%	0%	0%		Covering drains reduced exposure and related health risks through this pathway, and resulted in a major overall reduction in health risk due to significance of this pathway.
3a. Toilet and septic tank effluent to sewer (not drain)		0%			0%		0%		Reduction of faecal flows to open drain reduces subsequent exposure at local and community drains, but moves pathogen flows so increases risk at household due to no improvement in the sewer overflow/flooding.
3b. Improve conveyance (reduce flooding and leakage)			0%				0%		Reducing flooding and leakage reduces health risk in the immediate household area and in groundwater, although without improving treatment there was a slight increased downstream risk in waterways and food produce.
3c. Increase sewer discharge that reaches treatment plant	0%	0%	0%	0%			0%		There is a reduced health risk associated with downstream waterways and food produce, however the overall health risk reduction is medium, as this option fails to address risks associated with upstream pathways.
3d. Improve wastewater conveyance (3a, 3b and 3c)							0%		Addressing all issues with improved conveyance reduced the health risk associated with all pathways and results in a major overall reduction in health risk.
4a. Increase sludge emptying		0%			0%				Increasing sludge emptying frequency has the potential to increase risk, as unemptied (stored) sludge was assumed to have no exposure. While emptying benefits the septic tank effluent quality, (i.e., reduced pathogen hazard in this effluent), without also improving conveyance and sludge treatment the results show a significantly increased health risks in the downstream environment, so overall there was only a small reduction in health risk.
4b. Increase sludge emptying and its delivery to sludge treatment plant		0%			0%				Increasing emptying and delivery to treatment reduced health risk in the downstream environment, however the population exposed was small so the overall reduction in health risk is small.
5. Improve faecal sludge treatment and wastewater treatment	0%	0%	0%	0%			0%		Traditional treatment solution that only addresses downstream exposure pathways. This option only resulted in a small reduction in overall health risk since emptying and conveyance were unchanged.
6. Cover drains, reduce groundwater use, discontinue reuse of untreated sludge and wastewater for food production	0%			0%					A non-traditional solution that addresses the key exposure pathways and resulted in the highest overall reduction in health risk compared to the base case.
Legend:	Change in DALY pppy from base case	Improvement in health risk	Worsen health risk	Relative change	No change	Small (±1–3%)	Medium (±4–13%)	High (>14%)
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