Biofiltration as pre-treatment to water harvesting and recycling

Abstract

This paper presents the results of the long term biofilter experiments conducted with raw stormwater collected from a canal at Carlton, in Sydney. Anthracite and granular activated carbon (GAC) were used as a single filter media in biofilter columns. Media heights of 75 and 40 cm were used. The filter columns were operated at filtration velocities of 0.12 and 0.25 m/h. The removal efficiency for turbidity and DOC for the GAC filter media were found to be 75% and almost 100% respectively. The removal efficiency for the anthracite filter was much lower. Molecular weight distribution analysis showed an almost similar trend to the DOC removal. Compared with anthracite filter media, the GAC biofilter removed a much larger range of organic compounds present in the stormwater. The GAC biofilter removes organic matter earlier as compared to anthracite. Based on a limited sample of stormwater, the removal efficiency for phosphorus was upto 74% and that of nitrogen was up to 30%. In general GAC filter shows higher heavy metal removal efficiency than anthracite. The removal of zinc, iron, lead and nickel were good. However the concentration of heavy metal in the raw surface water sample was low.

Column studies on the removal of dissolved organic carbon, turbidity and heavy metals from stormwater using granular activated carbon

“…Anthracite was not tested because its properties tend to be inert toward heavy metals compared to GAC [16]. Initial metal concentration used in these experiments was 5 mg/L.…”

“…Nominal size ( mm) 0.3-2.38 1.0-1.1 [16], [2] Bulk density ( kg/m 3 ) 748 660-720 [2] Iodine number (mg /g.min) 800 - [2] BET surface area ( m 2 /g) 750 - [2] Maximum Moisture content (%) 5 -…”

“…High SS loading to the GAC filter may hinder its ability to effectively remove other pollutants such as organics from stormwater by clogging its active pores. Anthracite was chosen as a pretreatment filter material due to cost considerations and its ability to effectively remove suspended solids[16][17][18]. The flow rates of stormwater through the columns were 5 m/h, 10 m/h and 11.5 m/h, for 1-2 d, 3-4 d, and 5-6 d, respectively.…”

Modeling a pilot-scale bio-geo-filter for removing soluble nitrate

“…Depending on the type of pollutants, a series of biological and chemical activities take place in these PRBs to remove a wide range of organic and inorganic solutes (Soejima 2002). More than 110 pilot and field studies have been conducted on using PRBs worldwide (Parvinnia 2007;Yaman 2003;Mohammed et al 2010;Ghasemian 2010;Amini 1997;Harris 2004).…”

Influence of pH on Organic and Inorganic Colloids in Stormwater

“…While the particle-bound contaminants and their transport within the urban environment are reasonably well understood (Aryal et al, 2006;Kang et al, 2007;Badin et al, 2008), there has been limited understanding of colloidal particles in stormwater and the environmental influence of pH conditions on them (Grout et al, 1999;Zgheib et al, 2011). The stormwater pH range of 6 to 8 is common (Mohammed et al, 2011) but literature has reported pH values of less than 4.5 and also higher than 8.5 (Gupta et al, 1981). The existing stormwater literatures focus mostly on the particle-bound or dissolved phases of heavy metals, organics, pathogens or nutrients.…”