| Performance goal: Minimise metal contamination in drinking water. |
|---|
| Description: Metals usually occur naturally in small quantities in water. High concentrations of metals in water usually occur from contamination from industrial processes or leaching from water distribution systems. Acidic water is corrosive and can leach metals from pipes and fixtures (e.g. copper, lead, zinc). It can also damage metal pipes and cause other problems, such as a metallic or sour taste (water with a low pH may contain metals in addition to copper, lead and zinc). |
| Performance criteria: Metal contamination is controlled. Best practice levels: copper 0–0.002mg/L, lead 0mg/L, zinc 0–1.5mg/L Maximum acceptable levels: copper 0–0.6mg/L, lead 0–0.01mg/L, zinc 0–1.5mg/L |
| Minimum requirements |
| Measure annually. |
| If high levels are found, expand the analysis to include: antimony, arsenic, cadmium, chromium–as Cr (VI) and mercury. |
| If acidifying water: |
| Best practice options |
| If heavy metal contamination has been identified as an issue: |
| If concentrations are above maximum acceptable levels, apply a pre-treatment. See Table 17 (below) for a comparison of the effectiveness of pre-treatments against metals. |
Table 17. Effectiveness of pre-treatments against metals
| Effectiveness against metals | Metal ions | Copper | Lead | Zinc |
|---|---|---|---|---|
| Pre-treatment | ||||
| PP filter | – | – | – | – |
| Ceramic filter | – | – | – | – |
| Pleated filter | – | – | – | – |
| Rapid sand filters | – | – | – | – |
| Semi-rapid sand filters | – | – | – | – |
| Slow sand filters | – | – | – | – |
| Centrifugal filtration | – | – | – | – |
| PAC | L | L | L | L |
| GAC | L | L | L | L |
| BAC | L | L | L | L |
| Ion-exchange resins | L | MH | MH | MH |
| Chemical coagulates | L | L | L | L |
| Lime softening | L | L | L | L |
| Chemical oxidation | – | – | – | – |
| Reverse osmosis | H | H | H | H |
| Nanofiltration | – | – | – | – |
| Ultrafiltration | – | – | – | – |
| Microfiltration | – | – | – | – |
| Electrodialysis | LM | LM | LM | LM |
| Electrodialysis reversal | LM | LM | LM | LM |
| Capacitive deionisation | LM | LM | LM | LM |
| Membrane capacitive deionisation | LM | LM | LM | LM |
| Aeration | – | – | – | – |
| Electronic water conditioning | – | – | – | – |
| L: low, LM: low to moderate, M: moderate, MH: moderate to high, H: high, –: N/A | ||||
