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Water reuse: savings, opportunities and environmental balance

Extreme drought and rain shortage reduce the natural availability of the renewable water resource, to face such issues new concepts and technologies are developing, all aiming at the waste and unexploited water reuse

riutilizzo acqua

Global warming is one of the most palpable impacts of climate change. In particular, the year 2023 recorded the historical record for the global average temperature at 17,18°C.

These extreme temperatures are not a surprise, but are part of a consolidated historical temperature trend, which reports a correlation between global temperature anomalies, which are increasing, and rainfall anomalies, that are decreasing, exacerbated by the often catastrophic phenomena that are recorded in our country and in the world. Italy is not untouched by climate change and the consequences, due to its location in the heart of the Mediterranean, due to its morphological characteristics, has warmed and will continue to do so faster than the global average.

As a result, the Mediterranean area will become increasingly arid due to the combined effect of rainfall and increased evapotranspiration.

1. Map of Italian draught risk

The phenomenon of drought

Based on the data, which show the precipitation deficit, it can be seen that 10% of the national territory of the countries of Western Mediterranean Europe has been affected by severeextreme drought in the last two years and Italy is in 5th place with a share of 13.2% above the European average. Drought is therefore increasingly at the center of the public debate in Italy.

In particular, in the summer months, when it manifests its highest effects and due to these phenomena the International Energy Agency has estimated a reduction in water flows of -40% by 2050, which is substantiated by the reduction of the surface of the glaciers, the loss of the snowpack, the rise and increase in the temperature of the Mediterranean Sea.

Drought decree

The Italian national institutions have responded to the 2023 water crisis through the so-called Drought Decree-Law of 14 April, which aims to simplify and accelerate authorization procedures, with reference to the construction of water infrastructure and the efficiency of the Government’s and Regions’ response to the water crisis.

The Decree aims to increase the resilience of water systems and reduce the loss of these resources, increasing the useful volumes of reservoirs, creating water collection systems by reusing purified wastewater and introducing simplifications in the construction of desalination plants. In this regard, a Steering Committee has been set up composed by 7 Dicasteries, which will carry out a survey and identify the most urgent interventions to combat water resources.

Wastewater: a consistent resource

Wastewater consists of approximately 99% water and 1% suspended, colloidal and dissolved solids. Although the exact composition of wastewater varies depending on its sources and over time, water remains the main component up to date.

2. Waste water recovery cycle

Wastewater treatment generally receives little social and political attention among water supply challenges, in a context of entrenched scarcity, the effects of which can have a detrimental impact on supply availability, human health and the economy. Wastewater treatment can follow a centralized or decentralized approach. In centralized systems, wastewater is collected from a large number of users, such as in urban areas by treating one or more sites.

Collection-related costs account for more than 60% of the total budget for wastewater treatment in centralized systems. Legislative Decree 152/06 is a milestone, providing the foundations for fully establishing the limits, treatment capacities, and the most advanced systems, generally based on the principles of biological treatment with activated sludge that organically place themselves at the service of the “source” by returning treated and ultrafiltered water to use, in compliance with the said Decree, and also to EU Regulation 741/2020 and Drought Decree Law No. 68/2023.

The Aquabis project

Manzi Srl, with a deep experience in the field of wastewater treatment, both in the public and private sectors, has extensively researched and studied the recovery of water for irrigation use of the motorway service areas for fuels, where the adjacent areas are transformed into pleasant oases of entertainment along the road. Therefore are well suited both as a recovery lodging from wastewater treatment plants, rainwater treatment and reuse, roof rainwater treatment and recovery and the like.

3. Compared percentage balance between sources and users

The Aquabis project in service stations

Service stations have a significant consumption of water, generally due to the services of bars, toilets, car washes, irrigation of green areas. Through the introduction of water treatment systems, it is possible to recover a large part of the water otherwise directed to waste and discharge. Assuming an average service station, with a yard of 2000 square meters and coverage surfaces of 500 square meters, we can estimate a flow of rainwater on the same surfaces equal to 2250 cubic meters/year, based on an average rainfall of 10 mm for 90 days a year, or about 6 cubic meters per day if properly stored. For rainwater that falls on the yard, we can therefore implement the de-sanding/de-oiling treatment systems using our GNL model with final filtration on an activated carbon column mod.

Manual FCM or mod. FCA automatic, which allow the precipitated volume to be fully recovered. It will then be possible to send all the treated water to a storage tank and then re-use the accumulated water. It is also possible to recover the portion related to the roof through the Aquabis model treatment system that allows the filtration, accumulation and sterilization phases of the stored portion super efficiently in a single tank.

As far as wastewater is concerned, from bar and toilet services with 1000 users per day and car wash with a track and 3 self-service boxes for an average of 100 cars per day, we can reach a wastewater discharge of 35 cubic meters/day or 12775 cubic meters/year, of which about 25 cubic meters/day from bars, kitchens and toilets, while 10 cubic meters/day from the car wash service.

4. Water balance between total sources and users

As far as wastewater from bars, toilets and kitchens is concerned, the largest water consumption is related to toilets, which alone can account for 80-90% of total water consumption.

For the portion of water coming from bars, kitchens and toilets, through the use of a DFSBR model biological activated sludge purifier combined with MBR model ultrafiltration systems, it is possible to treat and reuse all or part of the water used. As far as the share coming from the car wash is concerned, it is possible through a mod. DCAR combined with sand/carbon filters mod. Manual FQCM or automatic FQCA, to reach a recovery of about 90% of the water used in the washing, so that it can be fed back into the washing circuit, guaranteeing a major net saving in the total water consumption.

Additionally, the recovered water can be used to irrigate the green areas of the station, as required by the Drought Decree, or pursuant to Ministerial Decree 183/05 it can be reused to refill the toilet flushing boxes or the machine-washing circuit. Assuming a reuse on a green area of the station of 500 square meters (with a consumption of 8 liters per square meter for irrigation), we would have a 4 cubic meters/d need for irrigation.

As far as the recovery on toilet cisterns is concerned, we can estimate a reuse of 22 cubic meters/day while for the car wash cycle, we can use 9 cubic meters/day of recycled water. We would therefore potentially have about 35 cubic meters/d of water to be reused, recoverable almost totally or in part using the systems mentioned above.

5. Integrated treatment/recovery system for waste water

Conclusion

The recycle and reuse of wastewater and rainwater, in the private and public sectors, offers incredible opportunities, posing a challenge to be faced in the present and in the future.

From the brief example given it can be seen how it is possible to recover and allocate water for various purposes that would otherwise simply be discharged to the final receptor. In addition to the significant environmental impact, the ever-increasing cost per cubic meter of water used poses interesting economic incentives, which make it increasingly convenient to focus on the reuse of a resource that is becoming increasingly scarce. Wastewater reuse solutions are becoming mandatory in various countries around the world and in Europe.

For example, in Andalusia, a local government ordinance prohibits the use of drinking water for irrigation and washing purposes from the beginning of 2024, especially in the hottest and driest months. And it is precisely in this region of Spain, in the Malaga area, that we have been able to support the needs of the project of recycling car wash water for recycling and/or irrigation with the supply of 24 plants called Acquabis, which have received considerable recognition by the end clients.

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