## 5 Approaches to Improve Biofilm-Based Wastewater Treatment
### Modification of Carriers to Promote Biofilm Adhesion

Table 1: Comparison of the performances of different biofilm reactors for the treatment of nitrogen and ammonium. Figure 4: Interaction between the carrier surface and bacterial cell surface: (**A**) electrostatic interaction between the cell surface and the carrier surface; (**B**) hydrogen bond formation between the bacterial cell surface and carrier surface [32]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Brands Name** & **Carrier Materials** & **Specific Surface Area** & **Dimensions (Depth mm \(\times\)** \\
**AnoxKaldnesTM K3**, & polyethylene & 500, 500 & 7.2 \(\times\) 9.1, 10 \(\times\) 25 \\ \hline
**AnoxKaldnesTM K1**, & polyethylene & 500, 500 & 7.2 \(\times\) 9.1, 10 \(\times\) 25 \\ \hline
**K5**, Biofilm Chip P, **ActivecellTM 450** & polyethylene & 800, 900, 402 & \(3.5\times 25,3\times 45,21\times 16\) \\ \hline
**AnoxKaldnesTM K2** & polyethylene & 350 & \(15\times 15\) \\ \hline
**AnoxKaldnessTM Matrix C2** & polyethylene & 220 & \(30\times 36\) \\ \hline
**AnoxKaldnessTM Biofilm Chip M** & polyethylene & 1200 & 2.2 \(\times\) 48 \\ \hline
**AnoxKaldnesTM Z200, Z400** & polyethylene & – & 30 mm diameter, 200 \(\upmu\)m (thickness), 30 mm diameter, 400 \(\upmu\)m (thickness) \\ \hline
**LINPOR** & polyurathane cubes & 270 & \(15\times 15\times 15\) \\ \hline
**LEVAPOR** & soft porous foam cubes & 20,000 & \(14\times 14\times 10\)–20 \(\times\) 20 \(\times\) 10 \\ \hline
**polypropylene multifaceted hollow balls** & polypropylene & - & 25 mm diameter \\ \hline ABC4 TM, ABC5 TM, **ActiveCellTM 515** & plastic & 600, 660, 515 & \(14\times 14\), \(12\times 12\), \(15\times 22\) \\ \hline
**BWT15 TM**, **BWTXTM**, **BiopporzTM**, **CM-10 DTM**, **ActiveCellTM 920** & plastic & 828, 640, 589, 750, 680 & \(15\times 15\times 5\), \(15\times 15\times 10\), \(14\times 18\), \(9\times 13\), \(15\times 15\times 10\) \\ \hline
**Biosphere N, Spira 12, 14,** **FLOCOR-RMP**, **AnoxKaldnessTM Matrix M2, **Natrix F3** & polyethylene & 800, 650, 600, 260, 220, 200 & \(9\times 13\), \(12\times 12\), \(14\times 14\), \(10\times 16\), \(50\times 64\), \(37\times 46\) \\ \hline
**Polyurethane sponge** & modified polyurethane sponge & 32,000 & 10,000 \(\times\) 10,000 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Popular carriers and their characteristics [59]. [PERSON] et al. [8] reported 98.86 \(\pm\) 0.7% ammonium removal under 35% saline conditions when modified sponge biocarriers (SB) were used in MBBRs. Moreover, the modified biocarriers were said to promote rapid microbial growth. [PERSON] et al. [62] also investigated the use of polyvinylidene fluoride (PVDF) foam carriers in MBBRs. The results showed that these carriers promoted biofilm growth while providing great biofilm protection from MBBRs, achieving 77% \(\pm\) 7% organic removal efficiency. An electrically bound biofilm reactor was also used to enhance the attachment of biofilms. [PERSON] et al. [63] reported a 79.3% biodegradation rate within 28 h and enhanced biofilm attachment by using an electrically bound biofilm reactor with an anode (nematic liquid crystal electrode) and three different cathodes (Al, Cu, and Pt).