Hydraulic Properties and Reduction of COD, Phosphorus and Nitrogen in a Sand Filter used for Greywater Treatment – Simulation and Verification

• A vertical flow sand filter is a simple, effective and inexpensive system for treating greywater. The performance of sand filters treating artificial greywater was tested in the laboratory over a time period of 113 days. The filters consisted of columns (0.2 m diameter) filled with sand to a height of 0.6 m. The hydraulic properties of the filters were measured as well as the inflow and outflow concentrations of COD, BOD5, total and phosphate phosphorus and total-, ammonia- and nitrate nitrogen. To get a better quantitative understanding of the treatment processes inside the filters, the HYDRUS-CW2D computer software was used to simulate the filters. The simulation of water flow through the filter could be well fitted to the measured flow by adjusting three model parameters: the air entry value, the pore size distribution index, and the pore connectivity parameter. For the COD reduction the simulated results agreed well with experimental data after an adjustment of the microbial lysis parameters of HYDRUS-CW2D. The simulated reduction of COD was 65 %, while a 72 % reduction was measured for the filters in the lab. Simulated reduction of phosphorus in the sand filter effluent corresponded well to the measured reduction: the simulated reduction of phosphorus was 72 % while the experimental filters achieved a 79 % reduction. Also, the simulated effluent concentrations of nitrate compared quite well to the measured values. Almost no reduction (4 %) in total nitrogen took place in the experimental filters, which agreed with the simulated reduction (0 %). For the phosphorus and nitrate components in HYDRUS-CW2D, so far no changes have been made to the default parameters.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Samhällsbyggnadsteknik -- Vattenteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Civil Engineering -- Water Engineering (hsv//eng)

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