Dr Richard Coulton, CEO of Siltbuster Process Solutions, the UK’s leading providers of effluent treatment solutions, explains why companies should review their wastewater treatment process, and shares some advice on how to go about it…
With corporate investment normally driven by production requirements it is easy to overlook the importance of investing in wastewater treatment. As a result many effluent treatment plants have suffered from under investment, with old poorly maintained plants operating over capacity. Plants operated in this manner are prone to breakdown and run an increased risk of causing an environmental incident.
With the potential fines for such environmental lapses now likely to be much higher, thanks to new guidelines introduced last year, most organisations would benefit from reviewing how they manage their wastewater disposal operations. Especially as such an exercise would not only reduce risk, but could also reduce operating costs.
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Such a review involves a three pronged approach that looks at:
- The risk of a plant failure resulting in an environmental incident
- Contingency planning to mitigate those risks
- Options for reducing effluent treatment costs.
The assessment should:
- Review the characteristics of the effluent under current and future production regimes, including planning for peak and seasonal production.
- Review the performance of the effluent treatment plant and consider the implication of production changes.
- Identify critical pinch points on the effluent plant and assess the practicality of installing standby equipment at these points. The cost of such systems is likely to be small compared to stopping production and the implication of an environmental prosecution.
- Develop a list of critical spares to be held on site.Assess whether the balance tank is sufficiently large to homogenise the water quality thereby minimising the risk of shock loading the effluent plant and providing emergency storage for when things go wrong.
- Review whether a “Divert or Calamity tank” to temporarily store strong/difficult to treat waste would be benefit. It can then be bled back into the water treatment plant at a manageable rate or tankered off site.
- Raise awareness of effluent treatment within the organisation by educating production personnel and managers on how the effluent plant works and its limitations thereby reducing the risk of Production causing an incident.
Wastewater Treatment Contingency Planning
Having critically reviewed the performance of the effluent plant the next step of the process is to put in place a contingency plan to mitigate the risk of an environmental incident in the unlikely event of incident. This should include checks for changes to effluent volume/characteristics and/or records of any incidents – plus other changes such as new shift patterns or a transient workforce, unreported spillages, changed production methods/cleaning agents can all affect the waste discharged.
A good plan will set out what to do should there be a plant failure – such as who to notify, whether the plant can be repaired without out stopping production, how to stop production if it cannot be repaired and so forth.
It will also identify where to mobilise emergency treatment from, be that temporary storage tanks, tankering off site to the nearest suitable waste acceptance site, or the hire of replacement effluent treatment technology.
Cost reduction
Beyond reviewing the performance of the existing plant and contingency planning, a more strategic approach to waste management can often lead to a reduction in wastewater disposal costs, particular where the discharge is to sewer. The charge levied by the receiving Utility Company is calculated using the Mogden Formula which takes into account not only the volume of wastewater discharged but also the pollution load (i.e. the suspended solids content and biological oxygen demand).
In many instances cost savings in trade effluent charges can be achieved by:
- Improved solids and fats oil and grease removal prior to discharging the effluent to sewer (depending on the nature of the wastewater savings of up to 40% are not untypical)
- Changing the product mix away from one that makes a disproportionate contribution to Mogden charges.
- Weighing-up the effect new product streams have on effluent volume and characteristics.
For example, a jam producer who starts producing pickles will generate a completely different effluent which could significantly increase trade effluent charges unless the existing treatment plant is modified.
Think energy
Legislation aside, there are plenty of good commercial reasons why companies should take a closer, and more strategic, look at how they manage their effluent. For the food industry, addressing this can prove to be not just a cost saving exercise but a revenue generator, with the biodegradable by-product from the water treatment plant forming a suitable feedstock for a waste to energy plant.
For instance Ballyrashane Creamery found that the high concentration of fat in wastewater generated from its milk and cream processing operations made the effluent treatment process less efficient. So it needed a way to recover the fat and was also keen to see if it could get some benefit from the recovered fat.
By deploying a DAF (Dissolved Air Flotation) Plant, integrated into the existing treatment system, it ensured a more consistent feed to the plant, with none of the issues previously associated with high fat concentration. DAF units are designed to remove suspended solids and FOGs (fats, oils, greases) from wastewater.
Micro-fine air bubbles (white water) encourage the fat to float to the surface of the unit, for removal by an automated mechanical scraper. Up to 20m3/hr of wastewater is continuously fed through the unit, with removal of the fat making a tremendous difference to the efficiency of the effluent treatment process downstream.
In this instance the company then uses the recovered fat as part of its energy strategy. The recovered fat is mixed with other sludges from the plant, before being pumped to their new offsite Anaerobic Digestion facility.
Due to its high calorific value, the fat is ideal for producing energy. Indeed, over twelve months, the facility will generate more than 7 million kWh, which equates to about 2% of the power used on the site.
Conclusion
Clearly, by taking a holistic approach to wastewater treatment most operators can reduce the risk of a plant failure causing an environmental incident. However, beyond this, many can also achieve cost savings through reduced off-site disposal costs and potentially diverting waste to energy.
