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Irrespective of treatment and filtration, the other physico-chemical quality parameters including TDS, conductivity, BOD, COD, metal and heavy metal content was found within the recommended level except for pH. The pH of cotton sari filtered water was 9.9; this might be due to the addition of 0.01% scallop powder (Table 3). On the other hand, bio-sand filtration showed acceptable pH levels (7.3–7.6) over sari filtered water (9.8–9.9). When MOSP was added to the water the resulting pH was recorded as 9.8–9.9. This water passes through sand, charcoal and gravel and comes into contact with organic matter, and the presence of charcoal may absorb some color and stone might add some minerals to the water and consequently, the pH was reduced to neutral. In contrast, the sari filter does not have these materials and thereby retains the higher pH. When sari filtered water was treated with MOSP followed by second filtration with bio-sand filtration, the pH was found to be within acceptable limits. All these experiments demonstrated that bio-sand filtration is a better choice than the sari filter in converting surface water to clean water.

Table 3

Comparison of physico-chemical characteristics of raw water and MOSP treated water followed by various filtrations with standard value

Physico-chemical parameterRaw water samplesMOSP treatment followed by bio-sand filtered waterMOSP treatment followed by sari filtered waterUS EPA Standard for drinking waterBSTI Standard
Color Gray to yellowish 15 (color unit) 15 (color unit) 15 (color unit) 5 (Haxen unit) 
Odor Odorous Odorless Odorless 3 threshold odor number Unobjectionable 
Taste Fishy-sour smelly Agreeable Agreeable Agreeable Agreeable 
pH 7.62–8.01 7.37–7.89 9.91–9.94 6.5–8.5 6.4–7.4 
TDS 259–374 232–241 131–155 500 500 
Conductivity μs/cm 750–780 620–640 260–380 NS NS 
BOD (mg/L) 2.1–2.5 2.71–2.76 2.79–2.80 5.0 5.0 
COD (mg/L) 2.214–3.195 2.27–2.31 2.84–2.91 40 40 
Iron (mg/L) 0.00 0.00 0.00 0.3 0.30 
Manganese (mg/L) 0.00 0.038–0.039 0.019–0.021 0.05 0.50 
Zinc (mg/L) 0.00 0.08–0.10 0.12–0.15 5.00 3.00 
Lead (mg/L) 0.0003–0.0004 0.0004 0.0003–0.004 0.015 0.01 
Arsenic (mg/L) 0.002–0.003 0.002 0.002 0.01 0.05 
Cadmium (mg/L) 0.00 0.00 0.00 0.005 0.003 
Physico-chemical parameterRaw water samplesMOSP treatment followed by bio-sand filtered waterMOSP treatment followed by sari filtered waterUS EPA Standard for drinking waterBSTI Standard
Color Gray to yellowish 15 (color unit) 15 (color unit) 15 (color unit) 5 (Haxen unit) 
Odor Odorous Odorless Odorless 3 threshold odor number Unobjectionable 
Taste Fishy-sour smelly Agreeable Agreeable Agreeable Agreeable 
pH 7.62–8.01 7.37–7.89 9.91–9.94 6.5–8.5 6.4–7.4 
TDS 259–374 232–241 131–155 500 500 
Conductivity μs/cm 750–780 620–640 260–380 NS NS 
BOD (mg/L) 2.1–2.5 2.71–2.76 2.79–2.80 5.0 5.0 
COD (mg/L) 2.214–3.195 2.27–2.31 2.84–2.91 40 40 
Iron (mg/L) 0.00 0.00 0.00 0.3 0.30 
Manganese (mg/L) 0.00 0.038–0.039 0.019–0.021 0.05 0.50 
Zinc (mg/L) 0.00 0.08–0.10 0.12–0.15 5.00 3.00 
Lead (mg/L) 0.0003–0.0004 0.0004 0.0003–0.004 0.015 0.01 
Arsenic (mg/L) 0.002–0.003 0.002 0.002 0.01 0.05 
Cadmium (mg/L) 0.00 0.00 0.00 0.005 0.003 

NS = no standard set yet.

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