## 3 Results and Discussion  
### Biofoam Visualisation, Description, and Filament Reduction by Biodefoamers  
Since PSW has a high FOG and protein content, both of which are sluggishly biodegradable and thus favor filamentous bacteria proliferation [26], _Nocardi_ spp., _Microthrix parvicella_, and Type 1863 organisms were inevitably the cause of a thick, brown stable foam--see Figure 2. In our previous study [21], the dominant biofoamers were _Nostocoida limicola_ (causes a scum layer), _Gordonia kroppenstedti_, _Candidatus Microthrix parvicella_ (FOG-accumulating bacterium), _Norcardioides instulae_, and _Bacteroides nordii_ determined using metagenomic analysis. Several types of biofoam can be observed in WWTPs. These types of foam depend on the characteristics of the wastewater. White or gray foam is generated when there is fresh sludge, and this type of foam is usually unstable. The prevalence of non-biodegradable synthetic defoamers is what causes the frothy foam, and gray pumice-like foam occurs due to recycled fine TSS from other downstream processes. Due to the availability of excess extracellular polysaccharides, a slimp/pasty foam develops. However, the current study also observed the presence of a dense, slimp, brown, stable foam that is produced by the excessive growth of _Nocardi_ spp., _Microthrix_, Type 1863 species, and lysis materials from flocs [23]. The secondary consequence of excessive filamentous microorganism growth is bulking, resulting in lousy settling and, thus, excessive solid thickening. This phenomenon can be mitigated by supplementing biodefoamers with antagonistic effects on filament-forming organisms within the AS. Biodefoamers are microbial bioproducts such as Extracellular polymeric substance (EPS). They are of microbial origin, and they biofloculate the sludge and fix the mycolata within the flocs, which prevents them from getting enough nutrients from the environment and prevents excessive growth. Additionally, these defoamers are readily available in the treated wastewater, meaning that they donot disrupt the ecosystem. The biodegradationers used in this study were antimicrobial toward filamentous organisms compared to synthetic defoamers, as reported elsewhere [21].  
Overall, it was of great importance to test the biodegradationers' ability to inhibit the growth of filament-forming organisms in the PSW and AS mixture to assess the compatibility of the biodegradationers with the PSW treatment system to be used. The highest growth inhibition of 1.39 L/mL was observed when the consortium biodegradationer was used--see Figure 3. This revealed that the consortium biodegradationer can withstand the presence of PSW and the AS community and thus cannot be destructed, neutralized, or inactivated [27; 28]. The literature reviewed showed that the inhibition of biodegradationers commonly occurs due to the production of other extracellular by-products [29]. The lowest growth inhibition of 1.32 L/mL was noticed when a biodfoamer produced by _Aeromonas vermii_ and _Klebsiella grimontii_ was used. This demonstrated that the biodfoamers produced by the consortium were functionally superior to those produced by other co-cultures.