Additional Info

• In operation since: 2006
• Type of wastewater treated: Industrial: other
• Type of wastewater (other): Methanol scrubber wash water
• Hydraulic load: 14 m³/day
• Organic load (PE): N/A
• Organic design load (kg BOD/day): 2.8 Kg/d
• Location: Aldbrough, Yorkshire, UK
• Client: Scottish and Southern Energy
• Stage 1 type: Vertical flow, non-saturated
• Stage 1 surface area (m²): 210
• Cost: £43,000
• Needs:

  AMEC were contracted to Scottish and Southern Energy to construct and commission an underground gas storage facility at Aldbrough in the East Riding of Yorkshire. Methanol is used as a part of the process and a Methanol Recovery Unit (MRU) allows it to be recycled. The MRU generates a low volume of effluent which is blended with other treated effluents and discharged from site. The effluent carries a relative low level of Methanol and Benzene which needs to be removed from the effluent stream prior to discharge. A number of options were considered for methanol removal but ultimately a reed bed treatment system was selected as the most suitable for the site, however there was little room available on the site.

  Flow and Loads	Influent Average	Influent Peak	Discharge Consent
  Flow           (m3/d)	14.4	19.2	0.6
  Methanol    (mg/l)	200	400	<60
  Benzene     (mg/l)	3	30	<45
  BOD            (mg/l)	-	-	<1

• Solution:

  Methanol is commonly used as a source of carbon in biological wastewater treatment systems which have a nutrient limited influent. So the reduction in methanol would not be an issue. Benzene also can be relatively easily degraded in wetland systems. The main challenge with this project was to design and install a system that would fit in the limited area available. A vertical flow system was selected as it required a much smaller footprint to achieve the required treatment compared to a horizontal flow system solution. Required land take was further reduced by the use of pre-cast concrete wall sections. Thus a 210m2 gravel based vertical flow bed was installed planted with Phragmites australis.

• Benefits:

  The complex nature of the site, with its operational and safety issues meant that the relatively simplicity of the reed bed treatment solution provided a low maintenance/ labour solution with low carbon footprint to mitigate and balance against the mechanical systems required for other site processes. This matched the general philosophy of the plant owner/ operators to use sustainable technologies where possible. The reed bed solution was made viable by the use of the compact vertical flow option.