Dairy gets breath of fresh air

Landia has helped a dairy to meet strict discharge consents with a submersible mixer, which has improved the mixing and aeration of the effluent plant's balance tank

A leading dairy manufacturer has sought the advice of Landia on the introduction of a submersible mixer for wastewater that required additional aeration before it went to a pump. According to Landia, this has helped the customer better meet a tight discharge consent by improving the mixing and aeration of the uprated effluent plant's balance tank.

Meadow Foods produces products such as concentrated skimmed milk, anhydrous milk fat, and butter. The company first appointed independent environmental science and engineering consultancy McDonald Stevens Associates (MSA) to review its effluent treatment options.

Expert advice was required, especially because the company had to meet a demanding consent limit for discharging final wastewater. Previously, when carrying out maintenance, Meadow Foods discovered that the outdated units left large amounts of settled sludge, which greatly reduced the tank's effectiveness.

MSA specialises in food and drink effluent treatment and was responsible for the design of the uprated effluent treatment plant, which called for the removal of the outdated units in favour of installing two Landia Air Jets. The new aerators were designed with a chopping system of the pump that prevents blocking of the ejector nozzle.

Landia's equipment transfers oxygen into the liquid to start and aid the biological process, cleaning the wastewater and keeping solids in suspension for treatment further along the process.

Jerad O'Pray, MSA's consultant responsible for the project, says: "By working closely alongside Meadow Foods and Landia, we have teamed up to bring about a first-class solution. This was demonstrated just recently when, during routine maintenance of the balance tank, virtually no solids were evident. And, since the redesigned plant has been commissioned, effluent quality has improved significantly."

Landia UK & Eire Director, Hugh Vaughan, adds: "None of this would have been achieved without proper consultation. A wrongly specified pump can also create plenty of problems in applications where hard-to-handle products such as meat can create foul odours.

When floating, dry matter gives off gases in a by-product's chamber. This is a place that not even the speediest or efficient maintenance crew relish the thought of visiting."

Floating aeration
To bring about more flexibility, Landia has recently introduced a floating version of its Air Jet aeration and mixing system, which is designed to be suspended on pontoons. This makes it suitable for lagoons when adjusting to liquid levels, combining an efficient air ejector with chopper pumps for optimum oxygen transfer rates.

It is also available as an externally mounted system for above-ground tanks, or as a free-standing or guide-rail mounted unit. Capable of handling sewage, stormwater, industrial effluent and agricultural waste, Landia says this aerator boasts vigorous mixing capabilities. This, it says, improves oxygen transfer and prevents sedimentation. According to the company, it is easy to install, even in flooded tanks, and suitable for operation where liquid levels vary.

"Virtually all users now demand a guarantee that equipment won't block or break down when dealing with problematical material such as rags," Vaughan says. "And what a fast rising number of users are finding to their benefit is that properly thought-out aeration is multi-purpose. During the past 18 months, we have seen a trend for us to provide aeration that will assist or create the biological process, as well as eliminate or reduce solids."

Farm aeration
Vaughan is still looking for an increase in the number of UK farms with aeration equipment, estimated at present to be lower than 20%. "The industry is getting there", he says. "We've been able to spell out the aeration facts at a couple of very good exhibitions this year

that the right combination of mixers and aerators can reduce odours by more than
90%. Not surprisingly perhaps, we've had a very good uptake.

"It's perhaps a bit ambitious to think that every slurry store will soon have mixing and aeration equipment that deals with the industry's infamous odour problems. However, the farmers we've worked with this year are fast seeing that properly treated slurry is a very valuable by-product with a high fertilizer value.

"Aeration equipment manufacturers need to keep showing farmers and all industrial sectors that our equipment is strong and durable enough to cope with harsh environments and that biogas and other waste and wastewater technologies should be embraced."

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