Guide to onsite industrial wastewater treatment
Tightening environmental standards and the rising cost of tankering wastewater mean more and more industrial process companies are taking control of their own treatment systems. However, many who have opted for onsite treatment facilities have had their fingers burned by badly planned and delivered projects.
WPL specialises in package wastewater treatment plants. Like many other equipment providers, it is being asked for extra assurances that its treatment systems will work. Technical director Andrew Baird has this advice for ensuring wastewater projects go smoothly and that the right system is put in place.
Do your sums
Operational costs associated with industrial effluent are not always fully appreciated, says Baird. “A lot of customers get a shock when they look at their return investment. It’s really important to fully understand what the cost will be, before you can decide if it’s a viable option.
“Chemicals and power consumption costs are often underestimated, as are variables like sludge production rates. If you end up with more sludge than you expect, your storage facilities may not be big enough and you’ll have to pay for more emptying. Also remember to match the size of your sludge storage to the size of tankers you can get on site to remove it.”
And remember to think about labour costs.
“You need to really think about how much labour is required for an industrial system. If you install a DAF [dissolved air flotation] system, you’ll probably need an operator on site who can intervene if the system fails or is at least on site every day. Have you incorporated this cost into your planning?”
Baird said oversights like this are common. “Commercial failures occur because people have not thought about the investment upfront and have not done their homework.”
Try before you buy
Discrepancies between designs and the delivery of a project can be avoided by conducting detailed reviews and pilots before building a permanent solution, said Baird. “Put simply, you need to know that what has been designed is going to work in real time, and fits in with the level of training your employees have had.
“We would start with a lab scale review to sample and test the effluent to get the correct dosing regime, before we get to an estimated cost for the project.
“After the lab work, we would strongly recommend a reasonably sized pilot trial. This allows us to really look closely at things like chemical, power consumption and sludge production giving a very accurate indication of how the plant will operate and the out-turn costs.”
WPL’s own pilot plants can be hired with trained operators, or training can be given and operated by site. As the plant doubles as emergency hire, it is designed for ease of installation and operation. Biological processes need to be installed for at least 12 weeks, though they are sometimes in place for months or even years. “The longest pilot we had in place was for three years. On one occasion the kit worked so well, the company wanted to use it permanently.”
One of WPL’s more recent projects was at a winery in Norfolk, which saw the development of an onsite biological treatment plant, following a successful 10-month trial. The winery routinely tankered wastewater offsite for treatment but can now treat a maximum 100m3/day, for discharge to sewer network. The pilot successfully demonstrated that the effluent could be biologically treated to the required standard, even though its composition can fluctuate widely.
Baird said: “The pilot plants are easy to install and they do tend to work well, allowing us to try lots of variations and do lots of tweaking. That helps us develop the full-scale design, so we can come up with a proposal and a fixed price.”
Baird says every onsite treatment facility should be piloted first. “Yes, pilots are expensive but they will save you money in the long run. I wouldn’t do an industrial application with having a trial.”
Many projects have been hampered by poor quality kit, according to Baird. “You get what you pay for. I’ve seen dewatering systems stop working after a month and some equipment mothballed when the operational complexities or ongoing costs are realised.
“A lot of it comes down to manufacturing, or people over-selling the technology into inappropriate applications, so think carefully before going ahead with purchasing. Get hard facts and data upfront and get advice and recommendations. Look for tried and tested equipment, with good customer reviews. Don’t be tempted to buy off-the-shelf as all sites differ and one piece of equipment does not fit all.
“Speak to people who’ve operated it. When it comes to wastewater treatment, you don’t want to be the first company to try a brand new piece of kit. You’re going to be spending a lot of money, anything from £5,000 to £150,000 or even a million, so you have to be careful and really do your homework.”
Train and maintain
Maintenance is of course one of the most important things, once the unit is up and running. But problems can occur due to a lack of operating knowledge.
Baird said: “People don’t always read the operating and maintenance manuals and they don’t send staff on the training sessions we set up. Perhaps they don’t view training as important, but it really is. Operators need that knowledge. Some of these pieces of kit are really specialist.”
Unrealistic expectations of what an onsite unit can handle can also lead to failures.
“There are incorrect assumptions of what a piece of kit will do, or what it can handle. The only thing that should go into wastewater treatment sites is wastewater, nothing else. No hair nets, tin cans, plastic cable ties or packaging materials
“We find all sorts of things wrapped round pumps – it could be that people lift up the gridding to dispose of things quickly. Education and ongoing training would really help prevent equipment and processes breaking down.”
Think about the future
Your new onsite treatment facility might meet required environmental and trade effluent standards now but will it in the future?
“Building in future-proofing, especially legislative, is a difficult thing to do as you can’t guess the future. You can assume that as pressure increases on the sewer network, the water company will increase charges, set stricter discharge standards or possibly stop industry going to its sewer. Ask the question of your supplier – what’s the next step in treatment? At some point in the future could I re-use this valuable resource?”