A Modern Look at the Problem
Wastewater generating at the plants of dairy industry are highly contaminated for the most part with organic substances. When the big volumes of such contaminated wastewater enters municipal wastewater treatment plant, it usually has an extremely negative impact on its operation causing the greatest harm to the biological treatment stage. To avoid follow-on emergencies at the sewage treatment plants, and as a result, environmental and municipal disasters, they are forced to constantly adapt to the work of dairy plants and incur associated expenses, which usually requires more funds than there is available. Therefore, the construction of local wastewater treatment facilities at milk processing plants is necessary for the proper operation of municipal wastewater treatment facilities.
However, municipal wastewater treatment facility may refuse to accept wastewater from a particular customer according to the current legislation in case of overloading the plant by specific pollutants in such wastewater or even to terminate the contract for wastewater services in case of a significant excess of maximum allowed pollutant concentration in wastewater when it may lead to disruption of wastewater treatment processes. Thus, the dairy industry plants in Ukraine have no choice but to build local treatment plants in a short time period, if they want to keep their business. Of course, not all of them has sufficient funds to build a full-cycle treatment plant that would allow achieving the quality of treated water in accordance with the requirements for its discharge.
A good solution to this problem is the construction of modular treatment plants, which makes it possible to divide the construction of wastewater treatment plant into few stages, and even to divide the stages themselves into separate lines, allowing the project to be implemented gradually. Implementation of just the first stage of wastewater treatment process will provide a high-quality buffering, mechanical and physical-chemical treatment of wastewater, significantly reducing the overall contamination level and getting rid of peak discharges. This ensures both protection from disconnection from the sewage system and huge fines for significant exceeding of maximum required contaminant concentrations.
An important aspect of the implementation of the first stage of treatment facilities is the quality level of engineering. The typical wastewater treatment methods for this stage and related equipment are highly reliable and have been demonstrating their good performance for several decades. However, incorrectly performed engineering calculations and incorrectly adjusted process parameters may lead to the high reagent and electricity consumption on the one hand and to the low treatment efficiency, on the other. Therefore, there may be a situation when despite the high capital and operating cost of the wastewater treatment plant, the company will continue to pay large fines for exceeding the limitations for contaminants discharge.
Engineers and technologists of the ESMIL Group understand the need for a rapid solution of the problem and achieving high economic and technological efficiency of the local treatment plants at the same time, and are constantly working to improve existing reliable technological solutions and the possibility of simplifying and reducing the capital cost of the projects. Up to now, several optimised solutions for milk processing plants based on the construction of the containerised modular wastewater treatment facilities were developed.
Modular Solutions and Container Design
Firstly, the modularity of the technology allows the customer to determine the number of lines and stages of treatment facilities to implement at a given time based on their financial resources. According to paragraph 3.6 of the “Rules of acceptance of wastewater into centralized sewage systems”, plants are protected from the termination of the contract for wastewater service in case of having an action plan for their wastewater contamination level to meet the requirements. The necessary equipment will be gradually and systematically added one by one, whenever possible, in accordance with the existed plan and corresponding contract between the plant and municipal wastewater treatment facilities.
Secondly, in case of increasing of the plant production capacities, it is possible to add a parallel wastewater treatment line without the high cost of complete modification of all treatment facilities, which can be very convenient for developing enterprises. In this case, container design eliminates any additional capital costs associated with the construction of additional building or the need to build the wastewater treatment facilities with the area greater than required taking in mind possible business expansion in the future.
Besides, container design has great advantages when there is a need to implement the treatment facilities in a short time with a limited budget. First of all, this allows significant reductions in capital cost and project implementation time due to the elimination of building and civil works. All they need is to lay the foundation and connect pipes and power to it. Equally important is the fact that container design leads to a significant reduction in the scope of design work, and hence the cost and time for the project implementation. Additionally, project implementation time is also reduced due to the simplification of delivery and installation works. Finally, thanks to container design, local wastewater treatment plants can be built at those facilities that have limited available space for their placement and at the sites where it was impossible to build at all.
The mobility of container solutions creates additional opportunities for the implementation of wastewater treatment facilities at enterprises. It allows to easily move treatment facilities from one place to another without the need for additional dismounting and remounting work. This allows changing the location of a piece of equipment to adapt to the development of the enterprise and the process flow design of both production and the treatment plant itself. Furthermore, companies that for one reason or another can not afford their wastewater treatment facilities, can rent them for a specified period with the possibility of further buying-out.
Advanced Modern Technologies
The process of pressure flotation is the foundation stone of the first stage of wastewater treatment in the dairy industry. The technology itself has been known for a long time and has hardly improved over the last few decades. But the growing need to save resources today has forced chemists and industrial engineers of ESMIL Group to optimise existing wastewater treatment systems as much as it possible.
First of all, the combination of experience collected during dozens of industrial research studies and implemented projects together with automation of detailed design calculations of process parameters allowed selecting the most optimal equipment for each particular flow: definition of a required stream pathway and possible density of the lamella block allows reducing the flotator capacity and its cost; accurate calculations of air consumption allow reducing the saturation unit, its cost and electricity consumption; perfect solutions for dosing white water and reagent solutions in the wastewater stream lead to improved treatment quality and reduced penalties for exceeding the requirements; intelligent systems of chemical treatment of wastewater allow reducing consumption of reagents and avoiding secondary pollution as much as possible.
In addition, to reduce the operating costs at wastewater treatment plants, sludge dewatering equipment can be applied. Reducing the generated sludge volume by several times, dewatering allows saving the cost of its transportation and disposal. The use of multi-disc screw dehydrators allows doing this in most economical way with the highest energy efficiency as well as lowest water and reagent consumption. It makes this type of equipment the most cost-effective investment in the industry to date.
MDQ ESMIL Tsurumi Multidisk Screw Dehydrator
Further stages of biological treatment can be simplified, reduced and automated as much as possible by using the membrane bioreactor technology (MBR). The development of ultrafiltration membrane technology allows increasing the reliability, treatment quality and lifespan of the treatment complexes, thus not turning the wastewater treatment facilities into the main part of the plant, and allowing the company to focus on milk processing.
As a final stage, modern reverse osmosis systems are being introduced more and more often in the food industry. The development of this technology and product market has significantly reduced both the capital and operating costs of the corresponding treatment systems, making the investments in such projects attractive in the long-term vision by restoring and reusing the treated water, saving fresh water, and eliminating the wastewater discharge.
Examples of Recent Projects
Last year, ESMIL together with its partners launched two similar projects for the construction of local wastewater treatment facilities for the milk processing plants. Wastewater sources with a flow rate of 1500 m3 per day (50 m3 per hour) at both butter-making plants were effluents formed during tank washing processes mixed with a permeate from serum nanofiltration processes.
A technological process including mechanical, physical-chemical and biological treatment, as well as sludge mechanical dewatering stage were designed for the plants. The first stage of implementation was successfully carried out in a short time period due to the container design and rapid installation and commissioning. Thanks to the compact arrangement of the equipment, the drum screen, the reagent preparation and dosing units for flotation and dewatering, as well as the dehydrator itself were placed inside the one container. The DAF unit was designed meeting the requirements for outdoor operation, adapted to weather conditions throughout the year and placed next to the container. The container, DAF unit as well as buffer and sludge tanks were placed on a foundation approximately 15 m long and 15 m wide.
ESMIL Modular Treatment Plants in container design based on a DAF unit
MDQ ESMIL Tsurumi Multi-disk Screw Dehydrator
Due to the modular design, the first stage of the treatment process was launched immediately after installation. Fine-tuning of the process allowed achieving a noteworthy reduction of COD for milk processing plants by an average of 46-60%, and the reduction of suspended solids down to 12-17 mg/l. The step-by-step method of project implementation made it possible to collect accurate data on the quality of pre-treated effluent for more detailed design of the next stage of biological treatment to avoid the risks associated with the inconsistency of an actual effluent quality with the estimated data.
After the completion and launch of the first stage, the second stage of the project was started at the sites. As for today, the installation has been completed and the commissioning works of the whole complex have started.
The problem of the lack of local treatment facilities at milk processing plants in Ukraine today harms both the operation of municipal treatment plants and the development of the industry in general. But the experience of successful step-by-step implementation of modular solutions for local wastewater treatment plants using advanced technological equipment in container design proves the possibility of its simple solution. Today, thanks to the use of modern technological solutions, any company is able to implement such projects without having large funds for the local wastewater treatment plant construction, while acting within the current legislation and current regulations in the industry.