A pilot-scale investigation of disinfection by-product precursors and trace organic removal mechanisms in ozone-biologically activated carbon treatment for potable reuse
Biologically enhanced granular activated carbon (BAC) is a promising wastewater post-treatment to produce a purified effluent suitable for recycle in the textile industry. Three small pilot scale filters were used, filled with three media (two adsorbent media and one non-adsorbent), to compare two different GACs and quantify the biomass contribution to organic removal and colour abatement. A demonstrative scale filter was tested in parallel to evaluate the influence of hydraulic parameters on BAC process efficiency. Biomass contribution was significant when an acclimated biofilm grew on particles; in all cases, wastewater decolorising was due to physical-chemical adsorption only; higher hydraulic load negatively affected the polishing process. Laboratory and semi-industrial scale tests were performed on textile fibres and fabrics using samples of the effluent from the demonstrative filter. The tests confirmed the suitability of the treated water for textile reuse.
Abstract
The merits of activated carbon for removal of organic compounds from wastewater have been well documented in the literature. On the other hand there is a lack of published data on the use of activated carbon for the removal of trace metals from wastewater.
Experiments were designed to assess the possibility that activated carbon treatment would remove aluminum, cadmium, chromium, cobalt, copper, iron, lead, manganese, mercury, nickel, silver and zinc from wastewater. All metals studied were tested over the pH range 3-11. Greater than 99.5% removal was achieved by pH adjustment and activated carbon treatment for most of the metals tested.
Organic and trace organic performance data for ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) at the Lake Arrowhead water reclamation pilot plant are analyzed to determine the treatment efficiency of these processes in an indirect potable reuse design. Four organic parameters were studied: dissolved organic carbon (DOC), ultra-violet absorbance at 254 nm (UV-254), SUVA and base neutral analysis (BNA).
UF and NF removed the larger compounds from the influent, but had no significant impact on the base neutral fraction with the exception of sterols. The RO process removed DOC and UV-absorbance compounds from the effluent to their respective detection limits. Base neutral compounds were significantly removed by RO, leaving at extremely low concentrations small molecular weight compounds, indicating indirect potable reuse is technically feasible.
Feasibility of electrochemical regeneration of activated carbon used in drinking water treatment plant. Reactor configuration design at a pilot scale