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Odour Control

The organic biofilter serves to polish remaining hydrogen sulphide and accommodate VOCs and other components.

The solution: A two stage odour management facility The solution to eliminating odour from the SRDRWS force main was to design and construct a sulphide stripping chamber with vapour phase odour control treatment. It accepts foul air from both the east entrance chamber and the sulphide stripping chamber. A stripping chamber is essentially a concrete structure with a serpentine flow arrangement (similar to a typical chlorine contact chamber) that is fitted with coarse bubble diffusers. Diffused air from turbocompressor blowers is used to strip the dissolved sulphide (and other odourous compounds) from the solution. This also adds dissolved oxygen into the wastewater, prior to discharge into the east entrance chamber, where it is mixed with City of Red Deer wastewater. It is estimated that up to 90% of the dissolved sulphide could be stripped and released in the chamber. The stripping chamber was designed for the 25-year (2035) peak pump cycle volume and to maximize contact time, which increases stripping process efficiency. While this provides an oversized chamber for current projected flows, it will accommodate future growth without the need for expansion. The odour and corrosion potential within the stripping chamber is extremely high because of the nature of its inwww.esemag.com

tended function, that is, to strip dissolved sulphide through turbulent aeration. Also, other organic odour compounds are present because of the severe anaerobic environment in the force main. To protect against hydrogen sulphide related corrosion, an integral high-density polyethylene (HDPE) liner was installed on all exposed concrete surfaces. Sizing for the stripping chamber included a cast-in-place concrete chamber 21 m long x 6 m wide. Two turbocompressor blowers (one duty, one standby) and the accompanying aeration equipment were sized for approximately 3,250 m3/h, to provide the air necessary to strip sulphide from solution. Air is withdrawn from the stripping chamber via two fibreglass reinforced plastic (FRP) exhaust fans (one duty, one standby) at a rate greater than the input aeration rate. This keeps a negative pressure inside the chamber while pulling air from the stripping chamber, attached east entrance chamber and 1050 mm CRD gravity trunk. This air is then sent to a vapour phase odour control system for treatment. The total airflow pulled from the stripping chamber is 4,600 m3/h. Given the high hydrogen sulphide concentrations from the sulphide stripping chamber, a single biofilter was not adequate to accommodate expected odour concentrations. Therefore, a two-stage system was required. The continued overleaf... November/December 2015 | 23

Environmental Science & Engineering Magazine (ESEMAG) November-December 2015  

This issue features articles covering: Eliminating force main odour, controlling micro-pollutants in drinking water, Calgary's new grit remo...

Environmental Science & Engineering Magazine (ESEMAG) November-December 2015  

This issue features articles covering: Eliminating force main odour, controlling micro-pollutants in drinking water, Calgary's new grit remo...