When we get engaged for what is eventually the replacement of a wastewater treatment plant in NZ, the first thing we discuss is influent sampling. Typically, no data has been collected for years. So we develop a relatively standard sampling plan depending on the treatment requirements – and give it to our client.
First question is “How long do we need to do this?”. The answer to this should be 1-2 years.
Second question is “Do we need to use a composite sampler or can we just take grabs?”. Answer to this is “it depends, but typically yes you should locate a composite sampler”
And the conversation goes back and forth like this for a bit until a small amount of sampling happens to produce the absolute bare minimum sample set one could ask for.
The point we want to convey is that Councils and industries should be sampling all the time. Its part of quality control. But beyond that, the amount of risk introduced into a plant design or a project by having a limited or non-representative data set far outweighs the cost savings of reduced sampling. Fixing a design flaw is expensive and putting risk on contractors results in conservative design practices which also costs money.
So rather than allow this problem to be perpetuated any further, Lutra will provide councils and industries our standard raw influent sampling plan for free. To be truthful, it’s not particularly valuable intellectual property as you can piece a lot of it together from online sources or simulation model software, and I would rather a client show up with a year of data. It will shortcut the risk discussion we have with clients several times a year.
To help you out with your wastewater sampling planning why not download the document below: