Meeting water discharge limits at the poultry plant
Poultry processing involves the use of quite some water, in ?the case of the new plant of Celler Land Frischgeflügel of the German Rothkötter Group in the town of Wietze, it is about 10 litres per slaughtered broiler. And that water isn’t exactly up to ?standard when it leaves the production plant. Meeting the ?discharge limits consistently after water treatment gives the plant its license to produce. That’s where the Dutch firm Aqua Industrial Water treatment got involved.
By Fabian Brockötter
When the Rothkötter integration was planning to step up production after it reached their ceiling at their Emsland processing plant, it went out and searched for a second location. That was not an easy task in densely populated Germany. Besides that, the company had some wishes of its own too. The plant should be at some distance from the existing Emsland plant to be able to compart their supply stream in case of veterinary blockages, it should be in an area where new farms could be developed and should be near to a potential market, in this case Berlin. Eventually Rothkötter found a suitable location in Wietze, a small village in the Hanover area. However, societal demands and government legislation had to be kept in mind when designing and constructing the plant. Waste water treatment was high on the agenda, knowing a nearby river could be used to discharge processed water, when it would be clean enough.
Discharge water quality should exceed the water quality of the river
Regulations prescribed that the discharge water quality should exceed the water quality of the river, meaning that the water treatment installation had to almost reach drinking water criteria. Waste water treatment is essential for the whole poultry processing operation; without water treatment the plant cannot run. With huge financial implications at stake the processing plant wanted a ‘double safe’ system. All the pumping equipment, sieves, power supply have a backup built into the design of the water treatment installation. In addition to that extra fire walls have been installed.
The Celler Land Frischgeflügel plant processes 13,500 broilers per hour on one line and uses two labour shifts per day. The building process began in 2010, in September 2011 the plant was in operation and since then grew to its maximal daily production by the beginning of 2013. This results in a constant stream of pinkish waste water rushing into a sieving and pumping station in the basement of the plant. That is where the work of the specialists begins. There is no margin for error, six days a week, up to 2000 m3 wastewater per day is leaving the plant. That is why the Rothkötter Group stayed with what they knew and hired the Dutch firm Aqua Industrial Water treatment, member of the MPS Group. This firm built and assists with the Emsland operation for 10 years, which is why Rothkötter trusted them with the Wietze plant as well.
Knowledge of the poultry plant
The realisation of an integrated waste water treatment plant starts with knowing what is happening in the plant. “Our experience, gained in over one hundred references in poultry teaches us what we have to do in the treatment process to meet the discharge limits’’, says Aqua process engineer Thomas Wijffels. Being involved in the building process from the start his firm was able to build a tailor-made treatment plant, tuned to the wishes of the client and to the demands of the legislators and take in building laws from the start as well. “The waste water contains solids, which we want to get rid of as soon as possible. All particles bigger than 1 mm are sieved out, before we pump the water from the processing plant to our treatment facility 500 meters away. This prevents potential blockage of pipes and pumping problems.’’
What remains is water which still contains the small particles, fat and blood, a total of maximum 2000 m3 per day. “This water is pumped into an equalisation basin. This holds up to six hours of water quantity, levelling out differences in quality, because during cleanup the water is of different composition than during regular processing hours.’’
Consistent composition of waste water
Having a flow of waste water of consistent composition entering the actual treatment phase, makes life easier and end results better. The first step of treatment is a physical chemical treatment resulting in coagulation of the remaining solids by adding chemicals such as iron chloride in a so called flocculator. When entering the dissolved air flotation basis the coagulated fat and protein will rise to the top and is scraped off, while heavier sand sinks to the bottom and leaves the tank via a screw. Wijffels: “The coagulated material contains about 75% of all organic pollution and is ideal material to put in a bio-digester.’’
With the last solids and some of the dissolved material removed, the water is pumped to an enormous holding tank, where bacteria work their magic. In two stages, one without extra oxygen and one with extra oxygen bacterial turn NO3 into nitrogen gas and oxidise organic compounds and nitrogen into CO2, both substances present in our atmosphere. “The only step that rests is to remove the bacteria in another dissolved air flotation basis from the treated water. They are scraped off just as the coagulated solids earlier in the process. What is left is clean water,” according to Wijffels. From a bacterial point of view this water is not of drinking quality, but with additional treatment it is a really high quality source for process water which can be used to wash trucks and in cooling towers. Celler Land Frischgeflügel chooses to discharge the water into the nearby river Aller, at 94 m3 per hour during standard operation.
The facility is tailored to the poultry processing operation, so apart from a holding tank of one day capacity to compensate for down time it is not over dimensioned. That said, the whole Wietze plant, including terrain and requested building permits incorporate the possibility to mirror the whole operation. For now Celler Land Frischgeflügel will run at full capacity for the coming time in the existing composition. Plans for further extension are for the future.
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