**Table 4.**

*Application of adsorption for POME polishing.*

*Promising Techniques for Wastewater Treatment and Water Quality Assessment*


#### **Table 5.**

*Application of coagulation-flocculation in POME treatment.*

Nevertheless, the residual aluminum and iron concentrations may inhibit the biological treatment process in wastewater due to the reduction of microorganism respiration rate and low organic matter elimination [38]. The drawbacks of these chemicals are high cost, non-biodegradable and possible adverse effect of the chemical. Recently, interests have shift to natural and biodegradable coagulants such as PGA, cotton, chitosan, natural seed gum, *Jatropha curcas* seeds, and *Moringa oleifera* [39–42]. It is because chemical coagulants are non-biodegradable, costly and not environmental-friendly. The coagulation technologies can also combine with other polishing technologies such as adsorption, membrane filtration and AOPs to achieve better pollutant removal. **Table 5** shows the application of coagulationflocculation for POME polishing.
