Seven questions to understand water reuse for Food & Beverage manufacturing
Are there technical prerequisites to setting up an industrial water reuse system?
One important prerequisite is to segregate sanitary wastewater (from showers or toilet flush, for example) from process effluents (from production). Normally, you know and can control the contaminants present in your process effluents (product, ingredients, cleaning agents, etc.), but you have no real control over what is contained in sanitary effluents.
The second important prerequisite is to ensure that you have fully optimised your water use and water treatment operations to make sure you are not needlessly wasting water. In fact, the cheapest way to save water is not to use it in the first place.
Finally, you need to clearly identify where you will be able to use the recycled water. This requires mapping the potential users and quantifying the amounts of water that can be reused.
Is the water that is recycled through such a system really safe for use in Food & Beverage products?
There is no reason why it cannot be done safely. However, it is important to identify the food safety hazards related to each water use. For example, reusing water in a cooling tower system for your refrigeration plant carries almost no food safety risk.
So, it is useful to start by categorising water uses in the factory according to risk of product or food contact:
Category 1 – No risk, or negligible risk, of food product contact
These uses typically include utility cooling systems (e.g. refrigerant cooling, external washing of trucks, urinal or toilet flushing, landscape irrigation of factory gardens). However, lack of food safety risk does not mean lack of risk. It is important to consider hazards to employees (e.g. Legionella in the cooling tower, risk of employee contact with water, etc.)
Category 2 – Low risk of food contact
This is where water is not intended for contact with food products or ingredients, but it can inadvertently happen. For example, water in a cooling circuit being used to cool down the product via a heat exchanger. If the heat exchanger leaks, it is possible that some water can enter into contact with the product.
There are usually safety systems in place, such as always ensuring that the product side of the heat exchanger has a higher pressure than the water side, but this cannot always be guaranteed. It is worth noting that water in cooling circuits, regardless of its source, is rarely of drinking water quality, so using recycled water does not really increase the risk.
Category 3 – High risk of food contact
Typically, this category includes water that is used to push the product, or clean or rinse product surfaces. It is not ingredient water but a small amount may end up in the product, causing potential food safety hazards.
Category 4 – Intended contact with food
This includes all water used as an ingredient and all water used directly in the preparation of food. You can also consider water used by employees for drinking or sanitation in this category, as it is water intended for consumption.
Industry practice is to focus water reuse on categories 1 and 2 and not consider uses in higher risk categories, although some companies go as far as reusing water in all four categories.
One exception is that water contact with raw materials can be considered low risk according to the processing stage. One obvious example is washing potatoes or other vegetables when they arrive at the factory from a farm. The potatoes are covered in dirt and debris so it is likely the water will make them less dirty rather than more.
What do international and local regulations specify regarding these systems?
Unfortunately, most countries do not have clear regulations on water recycling and reuse. For many, there is no great urgency to recycle water:
- Some countries, such as India, are much more open to these technologies by necessity, due to scarce water resources.
- Others, like the US, have different regulations depending on the local authority. In fact, the absence of coherent regulations is the most challenging issue when it comes to implementing water reuse systems.
In the end, most companies that want to set up such a system are proactive, reaching out to local authorities for guidance and developing a path to approval for their reuse scheme. However, this can be a real obstacle to industrial water reuse projects, as there is a lack of experience and knowledge on the side of both manufacturers and regulators.
It is therefore important to find a partner who can help you figure out how to set up a system that complies with local regulations, and help you navigate the different steps and requirements.
What steps are typically involved in setting up a water reuse or recycling system?
First of all, you need to focus on the water that presents the lowest risk of food product contact. In this regard, the most obvious use is cooling tower make-up water. For many Food & Beverage factories, this can be one of the largest uses of water and an excellent way to make large strides in reducing the water footprint.
Note that, whatever the identified use, it is helpful to carry out a risk analysis of the water use, to understand the food or other safety risks that need to be managed or overcome by the recycling system. The HACCP (Hazard Analysis and Critical Control Point) methodology routinely used in the food industry is a useful tool for this purpose.
Finally, it is vital to call on water treatment and recycling experts who can design a robust and failsafe recycling system to help you succeed in your water reuse project.
What technology is needed to set up an industrial water reuse system?
The technology needed for an industrial water reuse or recycling system depends on three criteria: the amount and type of contaminant in the effluent; the water quality required by the users; and the level of safety needed.
But typical “water treatment technologies” used in a water reuse system include:
- Pre-treatments, to remove solids and other debris, the primary objective being to protect downstream unit operations from damage or overloading.
- Secondary biological treatment. Biological wastewater treatments are the most effective methods to remove soluble organic substances and nutrients from the effluent. They are usually used to make water suitable for discharge in the environment.
- Advanced treatments, such as ultrafiltration (a membrane system capable of removing solids and microorganisms from the effluent), reverse osmosis (to remove dissolved salts and trace chemical constituent), and activated carbon or ion exchange.
- Disinfection and purification technologies, such as ultraviolet, ozone or chlorine based treatments, to make sure the water coming out of the system is microbiologically stable.
- Distribution system conditioning, such as stabilisation and pH adjustment, to avoid corrosion problems in the distribution network and the reuse process or utilities, and chemical addition for residual disinfection and mitigation of microbiological growth.
It is also important to consider that these treatments will produce “waste” streams that concentrate the pollutants. Therefore, a strategy to manage each of these streams must be included in the planning process to ensure the facility is meeting discharge requirements.
What kind of water savings can Food & Beverage manufacturers hope for?
The answer to this question depends on the number of water users and the amount of water they use:
- For cooling towers, this can be up to about 30% of site water use, depending on your sector
- For boilers, it can be up to 20% of site water use
- For an effluent cycle system, about 70% of the total effluent can be recovered and recycled.
Above 70%, costs increase significantly and the cost/benefit ratio becomes less favorable. In certain extreme cases, generally dictated by the inability to dispose of any reject streams, Zero Liquid Discharge (or ZLD) can be implemented. This technology enables reject streams to be processed further, increasing recovery to above 90%. However, implementing a ZLD system, which requires evaporators & crystallizers, increases the cost of the process and would generally require strong regulatory leverage.
What kind of costs does a water reuse system represent?
This too depends on the quality of the effluent you start with and whether it is treated to be discharged in the environment, for example, or treated to be discharged in a municipal sewer (in which case the quality of effluent will be lower).
Also, the more water treated for reuse, the more economical the recycled water will be per unit of treated water. Typically, Food & Beverage manufacturers can expect recycled water at the outlet to represent between one and two euros per cubic metre, which is roughly the same price as municipal water in many parts of the world.
Cost savings will be generated by avoiding both purchased water and discharged water. In many cases, the latter can represent a much larger proportion of cost.