Drawer compacted sand filter: a new and innovative method for on-site grey water treatment

Abstract

In this paper, results of a new sand filter design were presented. The drawer compacted sand filter (DCSF) is a modified design for a sand filter in which the sand layer is broken down into several layers, each of which is 10 cm high and placed in a movable drawer separated by a 10 cm space. A lab-scale DCSF was designed and operated for 330 days fed by synthetic grey water. The response of drawer sand filters to variable hydraulic and organic loading rates (HLR and OLR) in terms of biological oxygen demand (BOD₅), chemical oxygen demand (COD), total suspended solids (TSS), pH, electrical conductivity and Escherichia coli reductions were evaluated. The HLR was studied by increasing from 72 to 142 L m⁻² day⁻¹ and OLR was studied by increasing it from 23 to 30 g BOD₅ m⁻² day⁻¹ while keeping the HLR constant at 142 L m⁻² day⁻¹. Each loading regime was applied for 110 days. Results showed that DCSF was able to remove>90% of organic matter and total suspended solids for all doses. No significant difference was noticed in terms of overall filter efficiency between different loads for all parameters. Significant reduction in BOD₅ and COD (P<.05) was noticed after water was drained through the third drawer in all tested loads. The paper concludes that DCSF would be appropriate for use in dense urban areas as its footprint is small and is appropriate for a wide range of users because of its convenience and low maintenance requirements.

Keywords:

• synthetic grey water
• hydraulic load
• organic load
• permeability test
• drawer compacted sand filter

Acknowledgements

Authors thank the people of Royal Scientific Society (RSS), particularly the staff of environmental labs for their unlimited support. Special thank goes to Mrs Mervat Kamel from the microbiology unit in RSS for her kind assistance in coliforms analysis.

Notes

1. Manaseer crusher company.

2. The Middle East company for Silica.