## 1 Introduction
Additionally, these filters can remove bacteria, protozoa, and cysts at up to 1 L of clean water per minute. With efficient and continuous maintenance, the filter can last 3-6 years, depending on the quality of the water entering the system. According to the manufacturer, this filter can handle up to 500,000 L. However, VF-100 filters are suitable for filtering water with less than 50 NTU (turbidity). For higher turbidity levels, preliminary treatment (sedimentation, sand filtration, etc.) is necessary [5]. Filtration of water from the Red Dam reservoir using these filters failed as the feedwater was highly turbid (exceeding 50 NTU). Furthermore, the residents did not report their unsuccessful attempts and abandoned the filters. These filters have the potential to assist in water filtration and purification, but there is a necessity for preliminary filtration and establishing continuous and active communication with the community. The team considered two sustainable technologies for improving water turbidity and contaminant removal before using the VF-100 filters. The first is based on slow sand filters (SSFs). Sand filtration is a common process used to remove particles from water, ranging in size from nanometers to micrometers, and is suitable for community needs [6]. The mechanisms for particle removal in this filtration process are multifaceted, depending on the intricate interplay between the physical and chemical properties of the water, the characteristics of the suspended particles, and the composition of the filter medium. Particle removal primarily occurs through two main processes: size exclusion and adhesion. Size exclusion is a physical process where particles larger than the pore spaces of the filter medium are trapped and retained. This mechanism is influenced by the filter's pore size distribution and the shape and size of the particles in the water [6]. Conversely, adhesion involves electrostatic and van der Waals forces that act between the particles and the filter medium. As water flows through the filter, particles come into  
Figure 2: Images of local water sources for animal and human consumption: (**a**) Red Dam, mainly used to serve animals but also as a drinking water source for residents from some local villages; (**b**) Sokoru Dam (showing human consumption); (**c**) Sokoru Dam (showing animal consumption). close contact with the surfaces of the filter medium, where they can adhere due to these attractive forces. The effectiveness of adhesion is influenced by the surface chemistry of both the particles and the filter medium, including factors such as charge density, hydrophobicity, and the presence of chemical functional groups that can interact with the particles [7]. Additionally, other mechanisms, such as interception, where particles follow a streamline that brings them into direct contact with the filter medium, and diffusion, where small particles undergo Brownian motion and eventually collide with the filter surface, also play crucial roles in enhancing the overall filtration efficiency. These processes are further augmented by developing a biofilm layer on the filter medium over time, which can enhance particle capture through biological activity and the formation of a more complex surface structure [8; 9]. A biofilm-based SFF operates through a combination of mechanical and biological filtration mechanisms. The sand bed percolation mechanically filters particulate matter, while the biofilm layer provides biological filtration. This dual mechanism is particularly advantageous in rural settings where water sources may be contaminated with various pollutants, including pathogens, organic matter, and heavy metals [6; 7; 8]. Biofilms are complex assemblies of microorganisms, including bacteria, algae, and fungi, which adhere to the sand grains and produce extracellular polymeric substances (EPSs). EPSs include proteins, polysaccharides, and nucleic acids, creating a sticky matrix that physically binds and removes pathogens, bacteria, organic matter, viruses, and heavy metals [7; 8; 9].