# Innovative Approaches for Minimizing Disinfection
## 4 DBP Minimization Approaches
### Coagulation  
Coagulation operates by destabilizing NOM particles using positively charged metals, forming larger aggregates (flocs) that facilitate the settling of organic pollutants. This method effectively removes NOM from water through three main mechanisms: colloid destabilization, precipitation, and co-precipitation. Many water treatment plants employ iron salts (ferric chloride and ferrous chloride) and alum as coagulants. These coagulants aid in the settling of NOM, reducing the solid load on filters. Coagulation efficiency is influenced by factors such as coagulation conditions, NOM characteristics, the type and concentrations of inorganic compounds, and the design and operation of the treatment plant. Research indicates that ferric chloride is more effective in removing DOC than alum. The optimal pH for coagulation is around 5.25 for ferric chloride and 5.50 for alum. Additional treatments, such as filtration, are necessary to further reduce NOM and TOC [23]. Coagulation effectively reduces the concentration of high molecular weight organic matter, such as humic acids, while more minor organic compounds are typically removed through adsorption processes using activated carbon. Activated carbon also adsorbs substances that can act as precursors to DBPs. Therefore, combining both methods is advantageous as it helps reduce the organic matter content across a broad range of molecular weights. Generally, powdered activated carbon (PAC) is introduced into the treated water during coagulation. The entry point is the rapid mixing chamber, with activated carbon added after the coagulant [24]. In the coagulation stage of the water treatment process, coagulants like aluminum sulfate and ferric chloride are commonly used. The formed precipitate is then allowed to settle in a sedimentation basin before the water moves to the filtration stage, where disinfection occurs. However, studies conducted in Missouri have shown that in many small-scale utility facilities, the floc formed is often too small or lightweight to settle effectively. As a result, it carries over to the final clarification stage and enters the filtration stage, leading to more frequent backwashing cycles. This situation also allows for higher concentrations of TOC to react with the added chlorine, resulting in elevated levels of DBPs even before the treated water exits the treatment system. Factors such as detention time in the primary and secondary basins of a two-stage water treatment process, floc density (dense floc settles more readily), raw water quality, and the type and dosage of coagulant can all influence the effectiveness of the treatment process in removing TOC. This highlights the importance of optimizing the coagulation and sedimentation stages to maximize the removal of organic precursors, as their subsequent reaction with the disinfect can lead to potentially harmful DBPs in the finished drinking water [25]. According to [PERSON] et al. [14], the effectiveness of removal through coagulation can be influenced by the type of coagulants used and the physicochemical properties of NOM. The removal of DOC under conditions of enhanced coagulation with ferric chloride can reach up to 57%, which is significantly higher than that achieved with poly aluminum chloride. High-molecular-weight dissolved organic matter and hydrophobic dissolved organic matter are removed much more quickly than low-molecular-weight dissolved organic matter and hydrophilic matter. The interactions between the coagulant and NOM particles also affect the coagulation efficiency. Compared to prechlorination followed by coagulation, the effectiveness of DOC removal with coagulation followed by post-chlorination is higher. Although more DBPs are produced during post-chlorination than pre-chlorination at pH 7.5, fewer DBPs are produced at pH 5.5, highlighting the importance of pH control during the process [14].