The Cost Of Grit - the seven questions that WWTPs should be asking
Finding accurate evidence of the true cost of grit to a wastewater treatment plant may be a challenge for WWTP operators – especially when justifying the installation of more advanced removal technologies that take out more, finer grit before it does damage to downstream equipment and compromises processes like aeration and anaerobic digestion.
For too long, downstream grit has been reluctantly accepted as a fact of life, and its cost impact has been lost in regular annual maintenance and repair budgets.
Fortunately (or unfortunately, depending on how you look at it) the effects of grit on a wastewater treatment plant manifest themselves in a number of ways, so by asking the following seven questions operators can begin to identify, understand and, most importantly, tackle the issue.
Wastewater grit: the seven questions that operators should be asking
Many plant operators may not even realise that they have a problem with grit. Luckily, however, there are a number of factors that can act as warning signs that grit is accumulating or causing damage.
As a basic starting point, a treatment plant operator or engineering consultant should consider asking the following seven key questions:
Do you ever have to replace pumps, valves and other equipment due to abrasion wear?
Do you ever have to clean out pipes and channels because of accumulating debris at dwell points, or in long, low velocity flows?
Has the flow rate through your treatment plant diminished?
Has the efficiency of your essential processes, such as aeration tanks and anaerobic digesters, reduced?
Has your power consumption for moving water around the plant gone up by more than the cost of electricity?
Has your power consumption for aerobic flow treatment increased?
Have you invested in alternative, redundant plant so that you can take parts of your process offline for cleaning out and maintenance?
If the answer to any of these is yes then it may indicate that you have a problem with grit at your plant.
The first step to tackling problem grit is in identifying it. Modern, forward-looking wastwater treatment plant owners and operators are asking questions about plant operation and efficiency, and if the answers indicate that inefficiencies and reduced operating capacities may be due to grit, then they are looking to improve their grit removal technologies.
Grit costs money, and the sooner we can identify and address the grit problems that plague our plants, the more more effective - and cost-effective - our wastewater treatment will be.