Water in quarry : an ecological issue and a source of savings
Water is a rare and precious commodity.
Moreover, this liquid, which is essential to fauna, flora and human life, could well be lacking in the years to come, according to many experts in different countries.
The cause is global warming!
The latter is already having an increasing impact on the global landscape: intense, long and unprecedented periods of drought have appeared all over the world - including in areas that were previously spared from water shortages.
In this context, managing and optimizing the use of water in the quarries is both an ecological and economic priority.
For good reason, out of the 3,300 quarries present in France, nearly 1,750 wash materials for their production. However, the awareness of the importance of water management in quarry is not new for you, professionals of the sector!
For several years, this has been a major topic at the origin of many strategies to find an efficient water management.
At a time when every drop of water counts, Synaxe provides you with an update on water at quarry.
Water: a short-term issue for all quarries
More than 10% of total water consumption in Europe, this is what the mining and quarrying quarries, manufacturing and construction sectors accounted for in 2017.
By 2030, as an aggregates operator, you will need to increase the profitability of your quarry while minimizing its consumption of costly water resources.
Because it's a fact, whatever the sector, scarcity drives up prices!
However, it is impossible for your sector to do without water.
The washing of aggregates is an essential industrial step to remove the fine particles naturally contained in the deposits.
It is thanks to it that the aggregates acquire sufficient adhesion to be used with binders such as cement, lime or bitumen.
In the same way, water allows you to classify and correct the absorption of the aggregates and therefore allows you to meet the needs of the customers as well as the normative constraints.
Water from quarries : what exactly are we talking about?
Due to its use, water in quarry can be classified into five categories:
- Water withdrawal (water withdrawn underground or on the surface by the site for its treatment activities in addition to recycled water)
- Process water (incoming and outgoing water used in the production process)
- Water + fines (outgoing water to be recycled, as it contains the fines from the deposit following the washing of the aggregates)
- Recycled water (water which, after natural decantation or other recycling method, returns to the washing circuit)
- Associated water (rainwater, drainage, cleaning, sanitary and dust suppression)
Process water used for aggregate treatment and washing
Once washed, the value of the materials extracted from quarries increases considerably.
A fact that makes water all the more valuable!
However, in the face of the climate emergency and its impact on the availability of water worldwide, environmental regulations are tending to become stricter for operators of quarries.
For you, the challenge is no longer simply to have water, it is to ensure a regular supply of clean water to your treatment units by cost-effective means. While optimizing your water consumption to the maximum and guaranteeing an ultra-efficient recycling process.
To rise to this challenge, keep in mind three pieces of contextual information.
1. The quarries are not the only ones who need water!
As an operator of quarries, you are in direct competition with the water needs of urban populations, farms and the environment.
This competition is particularly noticeable in Australia.
As a reminder, the country has less than 1% of the world's freshwater resources while its population continues to grow - slowly but surely. Moreover, in recent years, the country's water supply has been severely threatened by the huge forest fires that have hit it.
As a reminder,forests supply 90% of the world's most populated cities with water!
Their fires have serious consequences for water supply. Each fire alters the amount of water coming from the forest and the seasonal timing of flows.
This further increases the value of the water.
And tomorrow?
Global climate projections suggest that the rate of fires is likely to increase and that water supplies are likely to become even less reliable - not least because of poor surface water quality. This situation is not unique to Australia. Canada and the United States are also increasingly concerned by this water issue.
2. The use of water in quarry is regulated by the European Union.
In 2012, the European Union launched an Action Plan to safeguard Europe's water resources.
The objective is to ensure the availability of sufficient quality water for all legitimate uses. Long before this plan, a specific regulation for the exploitation of quarries was created in 1993. This regulation aims to control the impacts related to the exploitation of quarries.
The risk of water pollution is at the top of the list!
In practice, the installations in quarries using process water are subject to the application of article 18.2.1 of the AM of September 22, 1994 for those subject to the authorization regime (installed capacity > 550kW).
Water regulations in quarry : 3 things to remember!
- The discharge of process water from the materials processing facilities is prohibited outside the authorized site.
- The water must be completely recycled.
- The recycling system must prevent any accidental pollution.
3. Wetlands from quarries are an asset for biodiversity
Water management in quarry is an opportunity for biodiversity!
The reason?
Material extraction and redevelopment work in the quarries create aquatic spaces and wetlands that are more or less floodable. These spaces can be colonized by fauna and flora that are currently threatened by drought.
Natural settling areas have proven their ecological value in active and redeveloped quarries . Natural gravity settling is a nature-based solution that offers three concrete advantages:
- The creation of environments rich in biodiversity (wetlands...)
- Land surface restitution
- Zero energy consumption
Ecological engineering is now an integral part of the quarries organization.
Since 1971, quarries has been obliged to rehabilitate its site. What does this mean? To restore a site that is both safe and well integrated into the landscape after the operation.
However, the last decades have proven that quarries is an opportunity to go much further in terms of ecology and biodiversity. Mainly thanks to their use of water! Ecological engineering makes it possible to rebuild natural environments conducive to sustainable biodiversity.
In practice, depending on the geographical and climatic context of a quarry, it is possible to orient the evolution of the site by favoring certain types of natural habitats.
For example, by creating as many gently sloping banks as possible to facilitate the establishment of macrophytes and species that prefer shallow depths, or by creating shoals and islands capable of hosting nesting birds.
Did you know that?
70% of the population of bank swallows in the Rhône-Alpes region lives in active quarries , according to the Ligue pour la Protection des Oiseaux.
Optimize water consumption in your quarry, it is possible!
1. By focusing on efficient water recycling
The water can be recycled via different methods: natural decantation, clarification, basin with regular cleaning...
In practice, the most effective recycling method is the one that takes into account the specificities of the site concerned (surface area usable for recycling, availability of water resources, need to create ecological zones during redevelopment, level of investment). Each recycling method offers advantages, but also requires a certain amount of vigilance with regard to the issues at stake at quarry.
The solution? Anticipate the benefits and concerns of the chosen recycling method at the design stage of the installation.
Don't miss out on technical innovations in water management!
Water is a global issue. That's why the innovation sector is multiplying solutions for water recycling and management. AquaCycle is the perfect proof! This water management solution reduces outdoor water consumption by recycling wastewater up to 90%. All this with immediate water recirculation in the process. Simple, compact and easy to use, the AquaCycle can be applied to both high and low tonnages in many markets. It also requires only 10% make-up water.
Coupled with the installation of two additional settling ponds to treat all the water used on the site, every drop of water present on the quarry will be optimized - both in its use and its recycling.
2. By using non-potable water
Not all quarries are located near a drinking water point. This is the case, for example, of the quarry massive eruptive rock site in La Mole, in the Var department. To obtain water, the site has been equipped with a 3,000 m3 storm water basin to collect rainwater.
3. By ensuring the good quality of the discharged water
The discharge of process water is prohibited outside the site of a quarry. Similarly, other water discharges (wastewater, cleaning water, etc.) are regulated by article 18.2.3 of the ministerial order. Their discharge is therefore subject to quality controls with imposed thresholds:
- pH between 5.5 and 8.5;
- temperature below 30°C ;
- Total suspended solids concentration (TSS) lower than 35 mg/l (NF T 90 105 standard);
- chemical oxygen demand (COD) concentration on unsettled effluent less than 125 mg/l (NF T 90 101 standard);
- hydrocarbon concentration lower than 10 mg/l (NF T 90 114 standard).
Think about it! 3 reliable solutions to ensure the quality of wastewater
- The installation of a second watertight area equipped with a large capacity hydrocarbon separator.
- The installation of retention tanks to store fuels and oils - ideal to prevent any risk of accidental pollution.
- Systematic analysis of water discharged into the natural environment.
Indispensable to quarries, water requires the greatest of attention for ecological reasons of course, but also economic. Fortunately, the more the years go by, the more the strategies of management and recycling of water in quarry are perfected! However, it is likely that water will continue to be an endangered resource in the years to come. Therefore, on the quarries side, the challenge is and will remain to continue the search for a fair balance between one's own water needs and those of the environment (fauna and flora included). A guarantee of economy and sustainability!
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