Abstract
The treatment of confectionary wastewaters by a biological aerobic treatment plant encountered strong failures when wastewaters concentration exceeded 30 g/l of chemical oxygen demand (COD), although the COD inlet flow remained under design specifications. Treatment performances stayed under 50%, and strong acid production and Hydrogen potential drop lead to heavy corrosion of equipments. During a laboratory scale study using the same organic load, with residence times ranging from 1 to 15 days, Hydrogen potential (pH) drop proved to be caused mainly by aerobic production of organic acids from sugars, leading thus to an auto-inhibiting process. The study demonstrated the influence of pH, acids and aeration rate upon key parameters as respiration rates and degradation kinetics. A reduction of 30 to 35 g/l of COD was obtained in laboratory scale reactors with pH and oxygen control. A comparison between the laboratory scale reactors and the full scale plant was made by measuring in the reactors the clean water oxygenation transfer rates and comparing its values to the data issuing from the plant. Compared to the data issuing from the full-scale wastewater treatment plant, the results of this study allowed giving recommendations for its upgrade.
Highlights
Wastewater concentration in confectionary factories may vary widely depending upon the products and the processes
If the treated water can be discharged to an existing domestic sewer connected to a wastewater treatment plants facility (WWTP), an aerobic high-rate pre-treatment may be chosen to avoid the investment in a separate complete WWTP and to minimize operation costs
This study demonstrated that in these conditions, a high uncontrolled production of organic acids intermediates by bacteria occurred even with high aeration rates
Summary
Wastewater concentration in confectionary factories may vary widely depending upon the products and the processes. As the main stream of wastewater issues from the washings, a consequence of water savings policies is the production of a relatively small volume of wastewater with a high organic content (primarily sugars). This high organic content is represented by high levels of chemical Oxygen demand (COD) and biological oxygen demand (BOD). In the present confectionary wastewater treatment case, a COD volumetric load of 6 kg COD/m3/d was designed to obtain a COD degradation rate limited to 70%, normally allowing the discharge of the pre-treated effluent to the sewer. The aeration equipments and tanks were out of work because of corrosion, and the WWTP was emptied
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
