Fresh Water for All!: Water Symbiosis in Food Industry to Combat Climate Change
Smart Technologies for Resource Management
“The fusion of ‘Big data’, the ‘Internet of Things’, and advanced analytics is providing manufacturers with unprecedented insights into manufacturing performance, customer behaviour, and new product development. Other enabling tools, such as cloud computing and cyber physical systems, have also been introduced as digital enablers in manufacturing. For example, cyber physical systems research can increase food consumption efficiency and the overall food production capability through precision agriculture, intelligent water management, and more efficient food distribution. Automation, intelligence, and collaborations are also relevant with particular reference to smart manufacturing, smart products/services, and smart cities.
Smart Technology for Water Symbiosis in Eco-Industrial Parks
Designing water symbiosis networks in an industrial site is aimed to solve the water quality and security problem by minimising freshwater consumption or pollutant discharge. However, implementing the symbiosis requires an expensive capital cost on the Eco-Industrial Park (EIP) site and may need cost compensation by the regulatory authority to facilitate the operation. The chemical engineers have been developing network models based on the use of game theory see for example [2], [3] to demonstrate the potential benefits and guidelines for each industrial plant, as well as the government, to derive a feasible cooperative policy to achieve the goal of environmental emissions reduction.
A new holistic framework for designing a cost-effective minimum water network is made possible by chemical engineers for industry and urban systems. The framework consists of five key steps, i.e. (1) Specify the limiting water data, (2) Determine MWR targets, (3) Screen process changes using water management hierarchy (WMH), (4) Apply Systematic Hierarchical Approach for Resilient Process Screening (SHARPS) strategy, and (5) Design water network; see [3] for more details.
Early works in this area were mainly based on the insight-based technique of pinch analysis (see [1], [2]) where a two-stage approach of flow rate targeting and network design was adopted. Apart from the previous “in-plant” based approach, various mathematical optimisation approaches have been developed by chemical process engineers over the past decade to complement the insight-based pinch approach in dealing with more complex problems, e.g. multi-contaminant systems, and complex operational constraints which include limiting the number of pipeline connections, forbidden/compulsory matches between water-using processes, process uncertainty, etc. Further extensions of these works are now been observed for inter-plant process water integration using pinch analysis and mathematical optimisation approaches; see [1],[2].
The industrial symbiosis network models, when used in conjunction with in-plant process optimisation models, provide a powerful holistic generic framework, applicable in all industry sectors including food production and processing [4], for minimising environmental emissions and containment of environmental pollution. These process models will continue to provide further inspiration for the chemical and process engineers to assume leading roles in environmental safety and protection.
Water Symbiosis in Food Manufacturing
The true cost of water for use in food processing is the cost of supply plus the cost of disposal, plus the loss of potential revenue from product discharged as effluent and the loss of energy with the discharged effluent; see [4]. Food processors may follow several strategies in order to reduce fresh water consumption and wastewater generation:
1) Development of unit operations that use less water, e.g., rotating rubber discs instead of conventional flood and spray systems for washing vegetables, use of steam for cleaning cans and glass jars in vegetable and fruit canneries, spray washing of meat and produce, and use of larger vessels due to their reduced specific surface, resulting in lower water use and waste load generated during cleaning processes.
2) Optimisation of the water circuit within the factory by, e.g., reducing uncontrolled water use during food processing and cleaning and improving layout design.
3) Direct recycling or reuse. Potential sources of water for reuse can be selected by assessing water usage and characteristics at the different unit operations of distributed food plants.
4) Recycling or reuse following reconditioning within an eco-industrial park network.
Reuse of food process water has been primarily limited to non-food and cleaning uses, such as general facility cleaning (e.g., water recovered from milk products by means of filtration) and performance of cooling functions and fire extinguishing purposes. However, process water may be recovered and recycled or reused directly or following treatment.
A variety of treatment technologies for food process water are now available providing a scientific basis for rational reclamation and reuse criteria. However, the systematic implementation of water reuse practices in the food industry is lagging behind due to i) the lack of guidelines, ii) lack of good quality control of treatment processes as well as iii) the lack of a consistent set of criteria to assess performance and allow for valid comparisons between alternative treatment technologies. Future research needs include, amongst other things, further development of water treatment methods, studies on microbial resistance to water treatment methods and evaluation of alternatives to chlorine for disinfection; see [4].
Water Network Analysis for Distributed Food Manufacturing
Use of food industry wastewaters for agricultural irrigation reuse is often reported. However, it will often be more optimal and effective to reuse these effluents within the same industry allowing for maximum industrial symbiosis; refer to Fig.1. Due to the wide variety of process steps and food products, food process water may contain a complex mixture of constituents, and this needs to be taken into account when considering recycling, reuse, reconditioning for recycling or reuse, wastewater treatment or discharge. The suitability of recovered water for use in any food operation is dictated by the i) quality of water required in that operation, ii) the quality of the used water, iii) the recovery and distribution method, and iv) the ability to recondition the water to the level required. Chemical and Process Engineers will continue to play a major role in modernising the water recovery and re-use in the food industry.
References
[1] Foo, D.C.Y., A state-of-the-art pinch analysis techniques for water network synthesis, 2009, Ind. Chem. Res., 48(11), 5125-5159, ACS Publ.
[2] Chew, I.M.L, Raymond R. Tan, Foo, D.C.Y., Chiu, A.S.F., 2009, Game theory approach to the analysis of inter-plant water integration in an eco-industrial park, Journal of Cleaner Production, 17, 1611-1619, Elsevier.
[3] Chin, H.H., Varbanov, P.S., Klemes, J.J., Bandyopadhyay, 2021, Subsidised water symbiosis of eco-industrial parks: A multi-stage game theory approach, Computers and Chemical Engineering, 155, 107539, Elsevier.
[4] Casani, S., Rouhany, M., Knochel, S., 2005, A discussion paper on challenges and limitations to water reuse and hygiene in the food industry, 39(6), 1134-1146, Elsevier.