A fly ash particles media filter for decentralized wastewater treatment systems Figene Ahmedi a, * and Petko Pelivanoski b a Department of Hydro-technic, Faculty of Civil Engineering and Architecture, University of Prishtina, Bregu i diellit p.n., 10000 Prishtinë, Kosovo b Department of Water Supply, Sewerage and Land Reclamation, Faculty of Civil Engineering, University Sts. Cyril and Methodius, Partizanski odredi 24, P.F.560 Skopje, Macedonia * Corresponding author. E-mail: figene.ahmedi@uni-pr.edu Abstract The contribution of this work is twofold: (i) estimation of the hydraulic operation of a coal combustion byproduct (CCBs) through its physical filtration by developing a physical model, and in broader terms, (ii) promoting the transformation of native disposal materials into beneficial materials. We developed an experiment which examines fly ash as a CCBs for its hydraulic performance, and runs in four main stages: First, fly ash in its natural state is tested in the laboratory to check if its effective size and uniformity coefficient match with recommendations in the literature; Then, fly ash of effective grain size as recommended in the literature is derived; Further, a physical model comprised of such a derived fly ash media filter and which supports horizontal flow of the effluent is developed; Finally, the hydraulic performance of the physical model comprised of derived fly ash in presence of effluent is evaluated and proved that fly ash is an appropriate media filter for hydraulic performance. The work clearly highlights the potential of the easy to reach and costless native fly ash as a media filter for treatment of wastewater which we consider a viable future work. Key words: fly ash, hydraulic operation, hydraulic properties, physical characteristics INTRODUCTION For small communities, small decentralized wastewater treatment systems are attractive since they are cost-effective and are considered a long-term option towards meeting public health and water quality goals (Cabanas 2009; EPA 2009). The most common decentralized on-site systems through which the small community’s wastewaters are managed are conventional systems such as septic tanks and sub- surface wastewater infiltration systems (SWIS). Septic tank provides primary treatment as long as SWIS provides secondary treatment of the effluent discharged by septic tank. There are some other on-site technologies, known as sand (media) filters and constructed wetlands, which provide advanced secondary treatment of septic tank effluent. The later are alternative technologies which are usually located after a septic tank and may substantially improve the quality of effluents, ensuring among others for lower nutrients concentration in the effluent (Crites & Tchobanoglous 1998) (Cucarella & Renman 2009). Generally, decentralized wastewater treatment systems are soil based systems. Tchobanoglous (2003) emphasizes that the use of soil for treating biochemical oxygen demand (BOD) and total suspended solids (TSS) was acceptable in the past, but in the twenty-first century, the use of solely soil for such a destination is not acceptable. Soil treatment capacity may be used for additional treatment of other constituents such as nitrogen and phosphorus and not only for BOD and TSS. Several studies contributed on utilization of gravel, sand and soil for pollutant reduction in decentralized wastewater treatment. On the other hand, it is also shown that water © IWA Publishing 2013 Water Practice & Technology Vol 8 No 3-4 350 doi: 10.2166/wpt.2013.035