# Recent Developments and Emerging Trends in Paint Industry Wastewater Treatment Methods
## 3 Paint Industry Wastewater Treatment Methods
### Physicochemical treatment
#### 3.1.1. Coagulation and Flocculation
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**Treatment Method** & **Treatment Parameters** & **Results** & **Source of Wastewater** & **References** \\ \hline Coagulation–floculation & _Brachystegia eturycoma_ (seed) & Process efficiency 96.50\% atcoagulant dosage of 5 g/L from a paint factory & Collected at batch production wash-off from a paint factory & [43] \\ \hline Adsorption using & Adsorbent wood ash pH = 2, contact time 3 h, 100 g/L wood ash & Pb removal efficiency—96.1\% maximum Co removal efficiency—99\% & From industry equalization & [44] \\ \hline Adsorption with & Adsorbent light expanded clay aggregate pH = 7 and exposure to 10 g/L of light expanded clay aggregate & Removal efficiency for Pb & Samples were taken from industry & \\ \hline \hline \end{tabular}
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Table 1: _Cont._filtration processes [8]. Results indicated the removal of COD 85%, TSS 91%, and BOD up to 90% using physicochemical treatment [10]. For latex paint industry wastewater, which is characterized by the high content of SS, bacteria, and COD, effective coagulant flocculants were aluminum polychloride and polyacrylamide. The treated water fulfilled the quality standards (COD removal of around 90%, TSS removal of almost 100%) and was proven usable for the production of different acrylic latex paints after disinfection with sodium hypochlorite (NaClO), reusing about 56% of the produced wastewater [39]. Bio-coagulants such as seeds, leaves, grains, and fruits of plants can enhance the coagulation process, mainly working by adsorption mechanisms, polymer bridging, and neutralizing charge, making the smaller suspended particles settle and collectible [40]. Bio-coagulants have lots of benefits such as cost-effectiveness [52], low sludge volume, ability to keep the pH constant, creation of toxin-free treated water, and biodegradability [23]. Natural coagulants and flocculants have a typically higher ability for making the flocs, therefore, a reduced amount is needed for the treatment process, which means their use can reduce the cost of the coagulation-floculation process. Several natural-based materials have been tested as flocculants. Limestone, pumice, sepiolite, bentonite, and mussel shell have been used in combination with FeCl\({}_{3}\cdot\)6H\({}_{2}\)O as flocculant aids, providing sufficient SS removal [51]. The use of the natural materials separately was reported to perform inadequately for dye removal. The combination of coagulant with sepiolite as a natural flocculant presented the highest reduction of COD (80%) in wastewater of paint and construction chemicals produced by a factory in Turkey [51]. The use of bio-coagulants, which are eco-friendly, in treatment processes is desirable because they are environmentally friendly and safe for human health. However, the optimization of the treatment process parameters is required for their efficient use in the treatment of industrial wastewater. One of the bio-coagulants effective for the coagulation-floculation processes, _Maerua Decumbent_ root extract has been used and the treatment process optimized [11]. The _Maerua Decumbent_ powder with several types of heteroatomic functional groups is useful for the removal of pollutants from wastewater. It is an eco-friendly and effective alternative to conventional coagulants. In optimum conditions, _Maerua_ root was reported to achieve the removal of turbidity by 99.2% and COD removal by 78.6%, which compared favorably with 98.6% turbidity and 66.2% COD removal using Al\({}_{2}\)(SO\({}_{4}\))\({}_{3}\). Additionally, lead and chromium were removed from the wastewater by 100 and 99.97%, respectively [11]. For comparison, another natural coagulant, aqueous extract of _Moring oleifera_ seeds (MOAE), fortified with Ca\({}^{2+}\) (CaCl\({}_{2}\) and Ca(NO\({}_{3}\))\({}_{2}\)), has been used for water-based paint wastewater treatment optimization combined with electrolysis. Results after applying the coagulation-floculation showed COD removal of 41% and turbidity removal of over 99%.