TABLE OF CONTENTS The types of impurities depend on the water source. The feed water could be groundwater, well water, surface water, seawater, brackish water, or municipal wastewater. Water composition of some typical waters is given in Table 2.1. Surface water usually contains suspended solids, colloids, and organics including high bacteria count, and has significant variable quality during the year. Groundwater and well water usually have low amounts of suspended matter but may contain iron, manganese, and hardness ions of calcium and magnesium. [10] Industrial waste-waters are regulated for suspended solids, free oil and grease, pH and biochemical oxygen demand, and heavy metals, and often contain mineral acidity, detergent compounds and trace amount of chemicals and heavy metals due to industrial pollutants. Membrane separation processes are being increasingly used to treat these waters for environmental pollution control. [11]
| Item/Ion | River [1] | Lake [2] | Well [3] | Brackish [4] | Seawater |
|---|---|---|---|---|---|
| Cations | |||||
| Calcium | 50 [*](125 [**]) | 38 | 114 | 129 | 400 |
| Magnesium | 14(57.4) | 8 | 19 | 89 | 1,252 |
| Sodium | 35(76.3) | 11 | - | 521 | 10,561 |
| Anions | |||||
| Bicarbonate | 158(129.5) | 117 | 170 | 161 | 140 |
| Carbonate | 1.2 (2) | 0 | 0 |
| 0 |
| Hydroxyl | - | - | - | - | - |
| Sulphate | 97(100.9) | 26 | 29 | 1,260 | 2,650 |
| Chloride | 16(22.6) | 18 | 76 | 262 | 18,980 |
| Nitrate | 4.6(3.7) | 1.8 |
|
| 1.5 |
| Fluoride | - | - | 0.1 |
| 1.4 |
| Boron | - | - |
| 2.8 | 4 |
| Other | |||||
| Silica | 13 (2.1) | 12 | 10 | 49 |
