8.7 Monitoring and analytical requirements

A quality-controlled system for management of drinking water treatment chemicals should be supported by appropriate testing and monitoring.

All chemicals used in water treatment should be tested, to check both the concentration of the active ingredients and the presence of contaminants relative to a specification. This is to ensure that the effectiveness of the treatment process, the quality of the water and the integrity of the assets are not compromised.

Requirements for testing by the manufacturer should be clearly defined in the specification, including testing methods. The amount, type of testing and whether NATA-certified results from an external laboratory are required may need to be negotiated to achieve a solution that is both effective and affordable. Clear statements as to the testing methods should be included in the specification. The specification should require test results to be available before the chemical delivery is unloaded at the water authority’s plant, to allow operational staff on site to reject delivery if specified requirements are not met.

Various physical characteristics can also be examined as part of the quality assurance program. Table 8.3 lists simple suggested acceptance criteria for some water treatment chemicals that could be applied by operational staff on site at the treatment plant. These criteria rely on human senses or simple equipment.

Table 8.3 Acceptance criteria for some water treatment chemicals

Chemical	Tests	Acceptance criteria
Aluminium chlorohydrates	Visual	Clear, colourless liquid
	Specific gravity	1.32–1.35 at 25°C
	pH	3.5–4.5
Aluminium sulfate (alum)	Visual	Clear colourless to pale brown (free of solids)
	Specific gravity	1.28–1.34 at 20°C
	pH	2.3–2.8
Ammonia	Visual	Colourless gas or liquid
	Specific gravity	0.8 as a liquid
Ammonium sulfate	Visual	Off-white crystal
	Specific gravity	1.77 at 20°C
Calcium hydroxide (hydrate lime)	Visual	Soft, white crystalline powder
	Solubility	0.165g/100g of saturated solution at 20°C
	Bulk density	450–560 kg/m³
Calcium hypochlorite	Visual	White crystalline solid, practically clear in water solution
	Specific gravity	2.35 in liquid
Calcium oxide (quick lime)	Visual	Grey-white solid (sometimes yellowish to brown)
	Specific gravity	3.2 – 3.4 as calcium hydroxide
	Bulk density	1030 kg/m³ (pebble); 1050 kg/m³ (powder)
Carbon, powder activated, granular activated (PAC/GAC)	Visual	Black solid (PAC 20-50 μm; GAC 0.7 – 1.2 mm)
	Density	250–600 kg/m³
Copper sulfate	Visual	Blue crystal, crystalline granule or powder
Ferric chloride	Visual	Brownish-yellow or orange crystalline form
	Specific gravity	42% solution: 1.45 at 20°C
	pH	42% solution: 1–2
Ferric sulfates	Visual	Yellow crystal or greyish-white powder, or a red-brown liquid solution.
	Specific gravity	Liquid solution: 1.5–1.6
Hydrochloric acid	Visual	Clear colourless to clear yellow (free of solids)
	Specific gravity	28% solution: 1.14 at 20°C
Hydrofluorosilicic acid (fluorosilicic acid)	Visual	Colourless to pale yellow liquid
	Specific gravity	22% solution: 1.18 at 20°C
Hydrogen peroxide	Visual	Colourless syrupy liquid (concentrations from 20% to 60%)
	Specific gravity	1.07–1.24 at 20°C
	pH	1–4
Hydroxylated ferric sulfate	Visual	Translucent, dark red (free of solids)
	Specific gravity	1.45–1.6 at 25°C
	pH	< 2
Polyacrylamides	Visual	White crystalline solid, supplied as a powder or aqueous solution, dispersed in light mineral oil
Polyaluminium chlorides (10%)	Visual	Pale yellow, slightly cloudy liquid
	Specific gravity	1.18–1.22 at 20°C
	pH	10% solution: 2.2–2.8
Polyaluminium silica sulfates	Visual	Slightly cloudy liquid, clear to yellow (free of solids)
	Specific gravity	1.32–1.36 at 25°C
	pH	2.8–3.6
Potassium permanganate	Visual	Odourless, dark purple crystal with blue metallic sheen
Sodium aluminates	Visual	White powder, or clear colourless to pale amber liquid
	Specific gravity	Liquid solution: 1.4–1.6
	pH	Liquid solution: 14
Sodium bicarbonate	Visual	White powder or crystalline lumps, soluble in water (60 g/L at 20°C)
	Specific gravity	2.159 at 20°C
	Solubility	96 g/L at 20°C
	Bulk density	1000 kg/m³
	pH	10 g/L solution: 8.4
Sodium carbonate (soda ash)	Visual	Greyish-white powder
	Bulk density	1000 kg/m³ (dense); 500 kg/m³ (light)
Sodium fluoride	Visual	White, odourless powder (or crystal), easily soluble in water
	Specific gravity	2.78 at 20°C
	Bulk density	1040 – 1440 kg/m³
	pH	1% solution – 6.5 4% solution – 7.6
Sodium fluorosilicate	Visual	White or yellowish white, odourless, crystalline powder
	Bulk density	880 – 1150 kg/m³
Sodium hexametaphosphate	Visual	White granular powder
	Bulk density	800–1500 kg/m³
Sodium hydroxide (caustic soda)	Visual	White, deliquescent solid)
	Specific gravity	30% solution: 1.33 46% solution: 1.48
Sodium hypochlorite	Visual	Pale yellow green
Sodium silicate	Visual	Lumps of greenish glass, white powders of varying degrees of solubility, or cloudy or clear liquids of varying viscosity
Sodium tripolyphosphate	Visual	White powder or granular solid
	pH	9.8 (aqueous solution) to 10.5 (slurry)
Sulfuric acid	Visual	Dense, oily, colourless to dark brown liquid.
	Specific gravity	1.2–1.85 at 20°C
Zinc orthophosphate	Visual	Clear odourless liquid