TABLE OF CONTENTS There are a wide range of non-biological unit processes, some of which are applicable to both water and wastewater treatment. Advanced processes are those not normally employed in conventional treatment but are required to conform to ever stricter water quality and discharge standards (Sections 8.1 and 8.3). Advanced water treatment processes include iron and manganese removal, softening, ion exchange, adsorption and chemical oxidation. Advanced (tertiary) wastewater treatment is more varied and includes biological processes for nitrification, denitrification and phosphorus removal (Section 18.4), as well as a range of physico-chemical processes (Table 20.1).
| Process | Removal function |
|---|---|
| Filtration | Suspended solids |
| Air stripping | Ammonia |
| Breakpoint chlorination | Ammonia |
| Ion exchange | Nitrate, dissolved inorganic solids |
| Chemical precipitation | Phosphorus, dissolved inorganic solids |
| Carbon adsorption | Toxic compounds, refractory organics |
| Chemical oxidation | Toxic compounds, refractory organics |
| Ultrafiltration | Dissolved inorganic solids |
| Reverse osmosis | Dissolved inorganic solids |
| Electrodialysis | Dissolved inorganic solids |
| Volatilization and gas stripping | Volatile organic compounds |
While sewage displays a diurnal variation in flow (Fig. 13.3), wastewater treatment plants are designed to handle normal variations of up to 3 times the dry weather flow (3DWF). The composition of the sewage entering large treatment plants also varies very little during this period. The exception is storm water which can result in an initial toxic shock loading as the stored contents of road-side gully pots are displaced...
