© Advetec 2018

Compact solution to bakery effluent

Food manufacturing and processing operations have made huge strides in cutting their environmental impact, cleaning up or reducing the effluent and wastewater they produce. Of course, it makes good business sense. But it’s a problem that isn’t going to go away and with increasing trade effluent charges and disposal costs, it’s an ever-present issue.
Take the bakery sector. Despite dietary pressures to cut fat and sugars our fondness for bread, cakes and pastries is unabated. Indeed, it’s a massive market producing millions of products each day to fill the supermarket shelves.

But as a food process industry it is also one of the largest water users, by far the biggest proportion of which is used for wash down and cleaning purposes. Loaded with fats, flour, sugars and yeast, treating this prior to discharge is essential to meet increasingly stringent environmental consents.

Of course, this isn’t a new issue and the largest bakery producers will have technologies in place to reduce the biological load in wastewater. Conventional solutions include screening and flow equalisation to accommodate production peaks, with FOG separation and Dissolved Air Flotation (DAF) systems to remove most suspended solids (SS). The installation of large Membrane Bioreactors (MBR), aeration tanks, filter plants and settlement tanks are typical.
While this produces clean water to meet sewer discharge consents, the resulting solids need further treatment, typically with an Activated Sludge process or similar system to digest the biodegradable components using indigenous micro-organisms. Failing that a waste service contract with a third party to remove and process the waste off site.

Although these systems work well they tend to be slow and take up a lot of space, requiring large storage, or settlement tanks to keep up with daily wastewater volumes, an issue if plant space is restricted. They also come with high capital and operational overheads, with a hands-on requirement to monitor and control the process both to ensure compliance with legislation and to make sure the process itself doesn’t become ineffective. This can be a major issue if unplanned or excessive quantities of waste liquid from production processes find their way into the effluent stream as high levels of fat, COD and pH can upset the delicate balance of the biological treatment process. Restarting the plant and correcting this can be lengthy and expensive, with a significant impact to production.

For some food medium size manufacturers, or where space is an issue, these systems simply may not be practical. It’s here that smaller, in vessel systems will increasingly have the answer.
One Yorkshire bakery business for example, which supplies baked goods to food service wholesalers, contract catering and major retail customers, has replaced its onsite effluent treatment facility with the latest generation of bio-reactor from environmental technology specialist Advetec.

This is a purpose built self-contained reactor which is plumbed in to the company’s existing effluent treatment system. A small footprint is especially advantageous and it relies on the Advetec micro-organisms to reduce the organic content within the effluent. It can achieve this at an accelerated rate and without the peripheral storage and balancing tanks that traditional systems require.

This is achieved in part by ensuring a waste flow through the Bio-reactor that constantly mixes and aerates the effluent, preventing suspended solids from settling out and maintaining dissolved oxygen levels. This maximises the digestive effectiveness of the system. But it is the company’s use of specially developed bio-stimulants that invigorate indigenous bacteria within the waste stream that makes the difference, an area that Advetec has specialised in. These bio-stimulants are matched to individual waste streams following laboratory testing, which significantly accelerates the process and delivers more effective reductions in organic concentrations.

The site in Yorkshire produces between 10 and 140m3 of wastewater per day, depending on production and this passes from the factory through a filter screen to remove film and other contaminants before entering the Bio-reactor. The main tank and mechanical components are constructed with 316 grade stainless steel to provide the necessary corrosive resistance to varying pH levels typical of bakery industry wastewater, and system monitoring with automatic dosing ensures an optimal internal environment for the process.
As well as a small foot print, the system also requires minimal maintenance, providing the composition of the effluent flow leaving the factory remains consistent and within design parameters. This is important and one of the reasons waste stream sampling and testing is crucial explains Advetec’s chief operating officer, Richard Goff.
Other than that a monthly check that dosing pumps and air compressors are working satisfactorily, and to monitor the level of micro-biological media in the dosing system, little intervention is required.

Installed in July 2017 the Advetec Bio-reactor has consistently ensured that the bakery meets its trade effluent discharge consent obligations, set by Yorkshire Water in accordance with the EU’s Integrated Pollution Prevention and Control (IPPC) directive. Both dissolved and particulate biodegradable components are removed during the process, reducing Biological and Chemical Oxygen Demand (BOD and COD) as well as total suspended solids (TSS). In addition fat and oil content is significantly reduced and odours are also suppressed during the process.
The Advetec Bio-Reactor is a bespoke solution designed and optimised for each site based on the composition and volume of the liquid effluent stream. The solution is also completely scalable. Richard Goff believes solutions like this will be increasingly relevant to small and medium food and drink manufacturers who need to take control of their wastewater stream. But as a replacement or supplementary solution, it will also appeal to existing effluent treatment plants where capacity deficits are an issue leading to repeated consent infringements or where old technology is increasingly ineffective.