substances and chemical groups that must be controlled in discharges to public sewers.
Paul Tipper added, “These Prescribed Processes and Substances Regulations do not allow the sewerage undertaker alone to set limits and the Environment Agency have to be consulted too. If these substances are present, issuing the permit may be delayed due to the additional consultation required. Gaining a temporary permit can take time as the risks need to be carefully assessed, so engaging with the sewerage undertaker at an early stage, like BAM Nuttall did, will prevent unnecessary delays or pressures to the project schedule.”
In a proactive demonstration of their environmental responsibility, BAM Nuttall, the principal contractor for the site QDS are currently operating on, undertake monitoring of wastewaters derived from their remediation activities across their sites prior to discharging them to sewer. On the current site, BAM Nuttall had made adequate capacity available in an existing gasholder base to store site wastewater should elevated concentrations of certain substances be encountered in water arisings that cannot adequately be addressed by the standard water treatment plant. This allowed other site activities to continue undisturbed whilst allowing feasible options to be sought to clean up the waters. This approach was applauded by United Utilities, the sewerage undertaker managing BAM Nuttall’s permit.
BAM Nuttall along with experienced environmental consultants Entec, turned towards specialist service provider QDS, who have a proven track record of designing award winning groundwater treatment schemes, to propose a solution. The project clock was ticking so both cost and timeframe were key factors under scrutiny.
Not being beholden to any particular remediation technology has given QDS the flexibility to successfully address a broad range of complex contaminated water scenarios. Remediation designs are tailored to individual sites and are based on client requirements, remediation targets and the performance criteria of the proposed technology. Traditional techniques along with innovative water treatment solutions, which have been pioneered and driven from the laboratory bench to full scale application by QDS, are considered and often combined to address a problem. Drawing on this in- house technical and engineering expertise, headed by Dr Joe Teer (Operations Director), QDS set about finding the most appropriate solution for this particular situation. In addition, it was recognised that this was an opportunity to examine how wastewater treatment systems are designed to give fit for purpose confidence to the permit holder and at the same time as to not be so elaborate that they weren’t financially viable.
Dr Teer remarked, “We were confident that, in this particular case, our approach of combining photocatalytic oxidation and ion exchange steps with some of the original wastewater equipment would give the necessary outcome. Our confidence was based on the work done prior to mobilisation to site. Soon after the enquiry came to us we recovered site water samples and undertook trials in the QDS
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in-house laboratory to clarify the details of the proposed treatment train. Not only did we focus on achieving the correct stoichiometry for any chemical reactions taking place but we also had to make sure that non-target substances did not compete with key contaminants during treatment.” QDS believe that you can’t plan for a standardised system because of the ever expanding list of substances of concern. QDS envisage having a short series of regenerative reactive exchange pods to tackle families of inorganic and organic contaminants. The onus will also be on the operator to manage the units to deal with spikes of irregular or rogue substances and high concentrations from waters derived from different activities on site, and to keep a balance between cost and environmental effectiveness.
BAM Nuttall confirmed, “The proposal submitted by QDS was sympathetic to both budget and programme, whilst satisfying all the demands of the permit. A collective volume of 1,000 m3
will take 10 working days of operation to treat,
which fits well with the time we have left on site and doesn’t slow us down elsewhere on site. The alternative option of removing the wastewater, untreated, by tankers doesn’t fit with our environmental commitments. In future, a more prudent approach will be to look for their support during the planning stages of remediation projects.”
As the imposing of ever more stringent criteria impact more directly on site activities, causing problems with deliverability, there is a genuine need for contractors to engage with water treatment specialists, such as QDS, and develop a team to address the effects of the ever imposing regulations. Dewatered arisings being discharged to sewer will continue to be commonplace at many remediation sites. However, should too much reliance be put upon traditional systems when faced with challenging discharge permit criteria, tight schedules and financial plans could be severely jeopardised.
As principal contractors, such as BAM Nuttall, and specialists, such as QDS, look to maintain high environmental standards, they realise that the status quo with respect to wastewater treatment on remediation sites is no longer adequate to meet the demands of the increasingly stringent requirements. To keep pace with ever changing regulations, a fresh flexible innovative approach is needed.
Photo: During wastewater treatment activities. Water volume has clearly decreased.
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