How do VFAs produced in all processes contribute to the environmental pollution? Essay

Recent evidences suggested that VFAs is commonly present in waste, landfill leachates and activated sludge (Manni et al., 1995, Lie et al., 1997, Siedlecka et al., 2008). Therefore, interest in determination of VFAs increases as it can be found at different environmental proceses. Wagner et al. (2014) claims that VFAs produced in all processes contribute to the pollution in many environmental parts such as air, water and soil. Analysis of VFAs range concentrations had been carried out in Polish municipal wastewater plants in Poland where the results investigations indicated that the higher VFAs are from the sample of landfill leachate while the lowest is from surface water (Siedlecka et al., 2008) (Table 2.4).
Table 2.4 The range of VFAs concentrations in wastewater and water
Type of waste Range of VFAs concentration (mg CH3COOH/L)
Municipal wastewater influent to biological treatment stage 65-168
Municipal wastewater influent to wastewater plant 28-69
Landfills leachate 0-19,000
Water from airport region collected in winter 52-25,000
Surface water 0-3
Source Siedlecka et al., (2008)
Guerero et al. (2012) stated that VFAs affects the storage stability of waste incineration residues by reducing the pH and directly increasing the heavy metal and radionuclides concentration. Mulkerrins et al. (2004) also reported that where the acetic and propionic acids increase the leaches of micronutrient in the water such as potassium (K) and sodium (Na) ions due to their good solubility. In addition, Idris et al. (2012) and Ehab et al., (2014) also propose that VFAs generated unpleasant odour in wastewater as well as sulfurs and amines compounds which influence by the bacterial activity.
According to Dhamodhoran and Ajay, (2014), the optimum VFAs is in the range of 2000-3000mg/L which can effects bacterias activity. Mino et al. (1984) and Comeau et al. (1987) found that VFAs is a source of carbon and plays an important role in removal of P from the wastewater. The existence of VFAs has been addressed in several small scale investigations where VFAs was found as the major contributing factors in P removal (Figure 2.9) (Mulkerrins et al., 2004 Alanis et al., 2010),
2.3.10 Types of microorganism
A bacterium taxonomy is significantly plays an important role in yielding information for phosphorus (P) removal (Nielsen et al., 1999 Noor Amaleena Mohamad et al., 2014). Microorganism that involves in phosphorus removal is known as phosphates accumulated organisms (PAOs). Previous studies by Cloete and Steyn (1988) had reported that Acinetobacter species is considered as PAOs that can be found in primary sludge which help in enhanced the biological phosphorus removal (BPR). This species can stored an excess amount of P compounds within intracellular materials (Sedlak, 1991 Szyrkowicz & Zilio-Grandi, 1995 Coats et al., 2011). Ohtake et al. (1985) also reported about 0.9 1.9% of dry weight of polyphosphate can be accumulated by these pure bacteria. These bacteria also reported as the major predominant microorganism in enhanced biological phosphorus removal (EBPR) process compared other heterotroph (Doran & Boyle, 1979 Lotter, 1985 Wentzel et al., 1986 Coats et al., 2011).