Removing Nutrients and Organic Compounds in Gray Water Using Multi-layer Sand Filter

Abstract

Background and purpose: Today, due to the reduction of water resources, separation of gray water from domestic wastewater and its reuse has gained more interest. The aim of this study was to apply multi-layer filtration (MLF) for removal of nutrients from gray water. Materials and methods: This laboratory-scale study was carried out in 2.3-19.2 gr. COD / L. d organic loading rates (OLR) over a period of 157 days. In this study, synthetic gray water was used as input to the multi-layer filter. The MLF system included three layers: sand, silica, and granular activated carbon. Furthermore, the scanning electron microscopy (SEM) images were used to determine the biofilm formation on the media surface. Results: The best removal efficiencies of COD, BOD5, TKN, and TP were 98.87, 99.84, 99.5, and 98% achieved in OLR 19.2, 12.8, (13.2, 4.6) gCOD/l.d, SOR 5.76, 2.88, and 5.77 m/hr, respectively. The study on the effect of loading rate revealed that by increase in OLR, the system efficiency to remove BOD5 and COD increased. Nevertheless, for TKN and TP, the efficiency decreased with increase in OLR. Also, according to SEM images, biofilm had grown well in the media, which can be effective in removing pollutants from gray water. Conclusion: Using multilayer filtration could be an appropriate option in removing nutrients from gray water in different loadings.

Keywords

• nutrients
• organic loading rate
• gray water
• multi-layer filtration