Questions and answers on water reuse

Water reuse is a part of integrated water management, and is technically possible to achieve already today, but harmonized EU level business/regulatory drivers are lacking. To ensure public health and environmental safety, we must standardize the quality of reused water, but not the technology to achieve it. The EU must facilitate innovation in water reuse, while considering the origin and destination of reused water – in short, the right quality for the right purposes.

1. What does water reuse mean in practice?

Water reuse means treatment and recycling of wastewater to be used in industrial processes, agriculture or in some cases for municipal purposes.

2. What are the main drivers for water reuse?

Main drivers for reusing water are 1) drought and scarcity of water supplies, 2) resource efficiency and 3) protection of existing water supplies.

1) Drought & water scarcity: In Europe, and especially in Southern Europe, drought is the main driver for water reuse. Treated wastewater is commonly used for irrigation purposes around the world due to drought and scarcity of water supplies. In Israel basically no municipal waste water is wasted. Municipal waste water is treated to a quality where it can be used in agriculture.

2) Resource efficiency: Not all water that is consumed in industry, agriculture or in municipality needs to be drinking water quality. Producing clean water from waste water in the long term can be more economical and sustainable than over consuming fresh water sources or desalinating sea water.

3) Resource efficiency: Treated wastewater can be used in many applications. For instance in the pulp and paper industry the water is reused several times and water consumption has dropped significantly over the years. In the 1970s producing 1 tonne of pulp required as much as 250m³ of water – now it only takes 5-50m³. The past decade saw water consumption of paper machines being reduced by 1/3 as a result of more efficient water circulation.

3. Can you reuse water in industrial production?

Yes, this is technically possible basically for all industrial processes. However the cost of reuse might be much higher than using other water sources.

Example #1: In food production the water used in the process needs to be drinking water quality. It does not matter if the water is from fresh water supplies or reused water. Human or animal health should be the first priority.
Example #2: Pharmaceutical and electronic industries need ultrapure water in their production processes. It is technically possible to produce this water also from waste streams but it could be too expensive, and therefore not advisable.

4. Can water be reused in municipalities?

Water is reused mainly in non-potable purposes, for example in irrigation or in domestic use such as toilet flushing. If the water is treated correctly it can be reused for various municipal purposes.

It is very rare that municipal wastewater is treated and directly reused as drinking water. However, in many places, treated water is indirectly reused. Around the world cities are producing drinking water from a lake or a river into which the treated wastewater is discharged back.

5. What are the benefits of water reuse?

Economic benefits: Designed correctly, recycling can help achieve considerable savings because water only needs to be treated for its purpose. For example, desalinating sea water for irrigation would be more energy demanding and expensive than using reclaimed water for the same purpose.
Social benefits: Water reuse can ensure the safeguarding of existing water supplies and to manage the imbalance between water demand and supply.
Ecological benefits: Water reuse can help to decrease the amount of waste water discharged into the environment. Ground water levels can be kept; overutilization of water from lakes can be avoided and in some cases nutrients in wastewater can be directly reused in agriculture.

6. What are the different water treatment methods for water reuse?

Depending on quality requirements and application of the treated water different methods are used. In many cases secondary and tertiary treatment (biological and chemical-physical) is enough. In other cases where quality demands (drinking water production) are higher, also membrane filtration (RO and UF) is commonly used. In all cases it is important to ensure that no pathogens are present. Therefore reused water should always be disinfected. Kemira has developed a disinfection method suitable for water reuse called KemConnect^TM DEX. It is a chlorine free disinfectant and minimizes the risk to produce potentially toxic disinfection by-products.

7. Is it safe to reuse water?

Yes, if the water is treated and disinfected according to WHO standards, EU’s Directives and other set standards for water quality. The quality of the water needs to be adapted according to the usage.

8. How common is water reuse in Europe?

In Europe, 2.4% of treated waste water (700M m³/year) is reused, mostly in Spain. Irrigation represents 75% of water reuse. And in areas with high water scarcity (Cyprus, France, Italy, Malta, Greece, Portugal, Spain), wastewater reuse is increasingly being used as a suitable alternative.*

9. What kinds of standards are needed in Europe?

Harmonized standards for water reuse are important, and we should focus on the quality of water, relevant to the ultimate application.

10. What does Kemira offer (products, know-how etc) for water reuse?

Kemira offers many products and application know-how for both wastewater and drinking water plants. Some examples are:

Coagulants are used for removal of particles, color, metals and phosphorus from water. Together with flocculants this is the most commonly used chemical in water and wastewater treatment, both if water is reused or not.
Flocculants support the coagulants but also could be used alone in some applications. Flocculants are also very important in sludge dewatering applications, ensuring that sludge can be handled and transported so valuable nutrients can be reused.
KemConnectTM DEX is mentioned above. This is a chlorine free disinfection agent suitable for disinfection of treated waste water but also for pre-treatment in membrane applications.
Antiscalants are used in many applications, in the water reuse field they can be used to support the membrane treatment and ensure that the membranes are protected from formation of deposits.