# Shifting from Conventional to Organic Filter Media in Wastewater Biofiltration Treatment: A Review
## 3 Filter Media Selection on the Efficiency of Biofililtration
### Drawbacks of a Conventional Media Compared to an Organic Media Biofiltration System  
The conventional filter materials widely utilized by several researchers throughout the past few years include gravel, sand, anthracite, GAC, expanded clay, and plastic media [26; 55; 69]. Although conventional media biofilters show remarkable performance in various water and wastewater treatments, there are numerous notable drawbacks and limitations worthwhile for consideration in further investigation. Figure 2 illustrates the main drawbacks of conventional media compared to organic media biofiltration systems. [PERSON] et al. [57] acknowledged that the cost of conventional filter materials such as gravel could reach up to 50% of the total investment cost of the biofiltration system, and is 100 times higher compared to organic waste materials. [PERSON] et al. [68] reported that the costs of conventional filter materials such as ceramic, anthracite, and GAC are 10.7 CS/m\({}^{3}\) (\(\approx\)8.44 US$/m\({}^{3}\)), 12 CS/m\({}^{3}\) (\(\approx\)9.46 US$/m\({}^{3}\)), and 55-60 CS/m\({}^{3}\) (\(\approx\)43.35-47.29 US$/m\({}^{3}\)), respectively, which are much more expensive compared to organic waste materials that are abundantly available as agricultural by-products. For example, coconut fibers as an organic filter media are natural agricultural by-products that are widely available in Southeast Asian countries such as Malaysia [63]. Utilizing these organic waste materials as an alternative to the conventional filter media not only reduces the operational and investment costs but also cuts down the natural solid waste generated throughout the world. In addition, the accumulation of biomass in conventional filter media creates several downsides such as clogging, large flow resistance, and poor permeability of the biofilm, which result in a decline in the removal performance of biofilter [96]. As an alternative, according to few reports [18; 93], utilizing organic materials as the filter media tends to reduce the clogging problem due to the achievement of a balance between degradation of the microorganisms and the retention of solids in the filter bed under lower organic loading. This observation is supported by [PERSON] et al. [94] stating that organic media,  
Figure 2: Drawbacks of conventional media compared to organic media biofiltration system. which have higher porosity for high loading rates and sufficient surface for the growth of the biofilm, show better potential to reduce the clogging problems compared to inorganic filter media. A conventional biofiltration system is further associated with the issue of a longer start-up period during the operation process. The natural biofilm present in the biofilter system comprises several mechanisms, which cause the biofilm to grow at a slower rate and result in a longer start-up period [97]. This limitation is supported by various researchers, as the maturation and acclimatization of biofilm varies, ranging from one month to half a year depending on the operational parameters [23]. Furthermore, biological nitrogen removal in a conventional biofiltration process involves heterotrophic denitrification which requires external carbon sources for electron supply; this includes methanol, acetate, glucose, and ethanol especially in treating sewage with a low pollutant concentration and a low C/N ratio. The accuracy of the additional quantities of external carbon sources remains one of the operational challenges as insufficient organic matter during the treatment process can reduce denitrification efficiencies, leading to the discharge of excessive nitrogenous compounds into the river, while the overdosing of external carbon sources causes an increase in the COD level in the treated effluent [98].