Table 2.

Groundwater iron variation at small geographical region (union-level) and residual-free chlorine levels in treated water in the small-scale study

Subdistrict	Union*	Iron concentration			Residual-free chlorine
		Median (IQR)†	Greater than 3 mg/L, n (%)	Intra-cluster correlation coefficient	Median (IQR)	Less than 0.2 mg/L, n (%)
Kaligonj (N = 48)‡	Kaligonj	1.6 (0.4–2.0)	2 (17)	0.04	1.3 (0.52–1.64)	2
	Muktarpur	4.3 (1.1–5.5)	8 (67)	0	0.14 (0.06–1.05)	8
	Nagari	1.3 (0.6–1.9)	0	0.3	1.26 (0.81–1.64)	0
	Tumulia	1.3 (0.8–1.6)	0	0.08	1.13 (0.50–1.75)	1
Kapasia (N = 120)‡	Barishaba	0.4 (0.3–1.1)	0	0	1.63 (1.54–1.79)	0
	Chandpur	1.6 (0.9–2.4)	2 (17)	0.24	0.26 (0.14–1.07)	4
	Durgapur	1.1 (0.5–5)	4 (33)	0.25	1.41 (0.49–1.57)	3
	Ghagotia	1.1 (0.5–1.5)	0	0.28	1.46 (0.21–1.61)	3
	Karihata	0.6 (0.3–3.7)	4 (33)	0.06	1.44 (1.08–1.61)	2
	Rayed	1.3 (0.6–2.9)	2 (17)	0.54	1.15 (0.54–1.65)	3
	Sanmania	1.4 (0.7–2.7)	3 (25)	0.09	1.64 (0.86–1.80)	0
	Singasree	1.2 (0.8–3.6)	5 (42)	0.45	1.60 (1.33–1.71)	1
	Toke	3.0 (1.3–3.6)	6 (50)	0.06	0.61 (0.05–1.34)	4
	Taragaon	0.9 (0.5–1.7)	2 (17)	0.12	1.38 (0.89–1.47)	0
Sreepur (N = 96)‡	Barami	1.4 (0.4–2.3)	0	0.12	1.56 (0.25–1.65)	3
	Gazipur	0.6 (0.3–1.1)	0	0.13	1.58 (1.32–1.79)	0
	Gosinga	1.2 (0.5–1.4)	0	0	1.11 (0.67–1.52)	0
	Kaoraid	0.9 (0.4–1.9)	2 (17)	0.36	1.11 (0.50–1.45)	2
	Mawna	0.8 (0.2–4.2)	4 (33)	0.42	1.67 (1.36–1.91)	0
	Prohladpur	1.8 (0.6–4.7)	4 (33)	0	1.31 (0.49–1.69)	2
	Rajbari	1.6 (1.0–3.6)	3 (33)	0	1.38 (0.59–1.74)	1
	Telihati	0.9 (0.5–5.0)	5 (42)	0.21	1.36(0.29–1.68)	3

^*Union: administrative unit of a subdistrict; for each union, 12 tube wells were sampled.

^†Interquartile range.

^‡Twelve tube wells tested in each village.