Food production processes rely heavily on good waste water bio-filtration solutions to reduce their trade effluent loads and minimize their environmental impact and reduce costs. H...
Bio-filter systems
Today, Trade Effluent Consents, pollution prevention and control (PPC) permits and Waste Management Licenses are all in place to protect the environment from pollutants. Emphasis on the environment is driving food production facilities to invest more and more in on-site effluent treatment plants to remove the contaminants in their waste streams and produce environmentally-safe, treated waste water. Installed by ACWA in the 1980s, the cereal manufacturer's existing bio-filtration system had achieved these goals of reduced charges and improved environmental performance; and operated seamlessly over its 30-year lifespan. However, despite the longevity of performance of the original bio-filter, the low pH of the starches in the cereal effluent eventually caused corrosion in the bio-filter's distribution arm and tank walls and called for replacement. The entire project involved decommissioning, demolishing and disposing of the existing bio-filtration solution safely and in an environmentally sensitive manner, as well as designing, supplying, installing and commissioning the new bio-filtration solution. The project took ACWA just eight months from start to finish. We were responsible for the turnkey design, build, testing and commissioning of the new bio-filter, plus refurbishment of the existing bio-filter sump and the system now treats the 1.2 million liters of effluent generated by the cereal facility each day and operates at a flow rate of 120m3 per hour. This energy efficient solution continues to treat liquid food effluent efficiently by itself rather than the company paying a third party to handle its waste. Bio-filter systems are available to handle various throughputs, and by investing in the new technology, food manufacturers of any size can tap into similar efficiency gains. Whether operating on a global scale or more locally, food manufacturers can achieve a dramatic reduction in the costs of their effluent treatment by installing a bio-filtration solution tailored to their needs.
Biofilm's effectiveness
Bio-filters are one of the most effective waste treatment technologies available today as they are relatively low cost, need very little operator input with only annual maintenance, and consume very little power. Suitable for use alongside or in conjunction with other technologies, bio-filters effectively process wastewater through screening, pH control, balancing, primary clarification, secondary biological treatment (bio-filtration) and secondary clarification to produce clean enough treated effluent that can go into the local watercourse. Essentially, the bio-filter is a bed of media on which a wide diversity of micro-organisms attaches and grows to form a biological layer called biofilm. This biofilm comprises different micro- and macro-organisms that stick to each other and to the surface of the media. Waste water to be treated is applied intermittently or continuously over the media, with organic matter and other water components diffusing into the biofilm where the treatment occurs, mostly by biodegradation.
Bio-filtration processes
Bio-filtration processes are usually aerobic, which means that micro-organisms require oxygen for their metabolism, and aeration occurs using the efficient natural flow of air through the process. To boost this, ACWA's bio-filters have been designed with a rigid structured plastic media that offers high specific surface area and good air/water distribution. Waste water is distributed over the media by a rotating distribution arm positioned above the media. To keep the biofilm moist and, therefore, the bio-filter micro-organisms healthy and productive, a proportion of waste water is constantly recirculated through the media. This ensures a minimum volume of waste water passes over the media, even at times of low influent flow. The new effluent treatment solution at the UK cereal producer features a new bio-tower, with enhanced material construction and a distribution arm that is now made of stainless steel. In addition, the installation of an inverter driven distribution mechanism allows variations in distributor speed that optimizes the waste water flow across the surface of the media. Critically, these improvements have been coupled with the use of structured media rather than the random packed media employed in ACWA's original bio-filtration system at the plant. Structured media offers a far more efficient bio-filtration solution as it allows effluent to be distributed more effectively throughout the filter bed. In addition, structured media can be walked on to allow operators improved access to waste water distribution mechanisms. ACWA's work at this cereal plant included refurbishment of the original biotower's three stage sumps, which were in poor condition having been subjected to the constantly low pH over their 30 years of operation. To provide further mitigation for the predominantly low pH of the starchy waste water entering the bio tower, the company ensured that an effective epoxy resin coating was applied to the concrete structure of the bio tower, the glass lined steel tank and distributor support column prior to installation of the media. All pipework was sized to give the lowest possible pressure drop whilst maintaining a fluid velocity higher than the deposit velocity of any suspended solids. Throughout the installation, pipe lines containing a high solids loading were sized to encourage a fluid velocity of 2 m per second and all other lines were sized to give minimum fluid velocities of 1-2 m per second. With the increasing pressure being brought to bear on food and beverage manufacturers in terms of their water treatment, partnering with an expert is vital to ensuring the optimum water treatment solution is found for each waste water challenge.
Email: bhastings@acwa.co.uk
Web: www.acwa.co.uk