Among the industries using large quantities of water for their processes are the following:
- Mining: The wastewater ponds or tailings present on mining sites are a source of concentrated and varied contamination. Their treatment is complicated but can present a very interesting return on investment!
- Pharmaceutical: The pharmaceutical industry often requires extremely pure water and sometimes uses chemicals that can remain in the effluent.
- Pulp and paper: The quantities of water used in this sector are phenomenal and must be treated adequately since their discharges are contaminated with heavy metals, flammable solvents, and paint residues.
Obviously, this list does not include all industries that use water in their manufacturing processes and the associated descriptions are brief. For more information, we invite you to visit the articles presenting wastewater management in specific sectors.
Although wastewater can come from a variety of sources such as the residential or natural sector, this article is intended to present industrial effluents and their management.
What’s an effluent?
When any industry needs to use water in any manufacturing process, the contact of the water with various gaseous, liquid, or solid contaminants creates what is called effluent. In other words, effluent is defined as the wastewater produced and discharged by the various industries.
Manufacturing effluents are pollutants from the various industrial manufacturing processes. The particulars effluents are those which must be separated from the "normal" effluents in order to be treated in a different way due to their composition, one can think of the condensates of paper mill. Then come the utility effluents and the occasional discharges. These two types of effluents represent smaller quantities but can be extremely concentrated and problematic since they are difficult to control.
Whether hazardous or non-hazardous, the discharge of these effluents can have significant consequences if not properly managed. There are two possible options when a company has to discharge effluent. The first option is to discharge in the local sewer systems, while the second is to discharge in nature. In both cases, the discharge of poorly treated effluent can adversely affect local aquatic life, flora, and human health. Therefore, it is important to understand the potential impacts associated with industrial wastewater management.
Types of discharges
Whether in nature or in a sewer system, the discharge of effluent is subject to government restrictions. In-kind spill are managed by both the federal and provincial governments to ensure standardization of obligations across the country. In contrast, sewage discharge is under provincial jurisdiction, but authority has been delegated to cities and ministries monitor and set standards.
There are no rules requiring a particular type of discharge. Regardless of the type of industry, if the laws and regulations are respected, it can choose either type of discharge. On the other hand, the geographical situation of certain industries often pushes them to opt for the spill in kind if they do not have access to a sewer system.
Discharges in the sewer system
Sewer systems are usually designed in two different ways. Combined sewer systems and sanitary sewer systems. Combined sewer systems combine domestic and industrial wastewater with stormwater. This type of system can be problematic during periods of heavy rainfall as overflow from overloading the system can result in raw sewage spilling into surface waters. In addition, separate sewer systems separate the inflow of domestic and industrial water from stormwater.
Municipal water treatment plants are generally well suited to treat normal domestic discharges. However, industrial effluents may be incompatible with the treatment processes used. For example, the discharge of some effluents into local sewer systems can pose risks to operating personnel and treatment equipment. Due to these potential complications, municipalities have a responsibility to develop a wastewater management system that ensures a constant and safe supply of water.
The discharge of industrial effluent into municipal sewer systems is often associated with downstream problems. Difficulty in monitoring effluent is an issue related to industrial discharges. For example, hospitals are required to comply with the Biomedical Waste Regulation but cannot be controlled or monitored. In addition, the difficulty in monitoring industrial effluents is amplified by three factors: heterogeneity, variability and aging of samples.
Heterogeneity is due to multiple sources of effluent landing in the same location. Organic and non-organic, soluble, and non-soluble materials mix to create a diverse effluent mixture. Variability is related to fluctuations in effluent quantity and quality. It can therefore be considered in time and space since, depending on the type of industry, the spill can vary greatly with the seasons or contracts. Finally, the phenomenon of aging of the samples can cause changes in the original effluents since the phenomena of flocculation, adsorption and decantation can modify certain parameters present in the effluent. In addition to these natural phenomena, redox and biodegradation by microorganisms present in the water can also cause significant changes in the composition of the samples.
In addition to the monitoring problems caused by changes in effluent composition, high concentrations of many contaminants can make it difficult to detect micropollutants. To add to the difficulty of identifying micropollutants, the variability of parameters present in industrial effluents is much greater than in residential effluents.
To overcome these difficulties, cities have been granted different legislative powers to optimize the efficiency of wastewater management, depending on the individual situation in each municipality.
First, it is important to remember that every municipality has the power to install and manage collective wastewater collection and treatment services throughout its territory. This power is set out in several laws such as the Cities and Towns Act, the Municipal Code of Quebec, the Municipal Powers Act, the Act respecting land use planning and development and the Environment Quality Act. Although this list is not exhaustive, it presents a good part of the Quebec legislation granting cities the power to manage sewer systems. It should be noted that for the construction of a sewer system or the installation of water treatment equipment, cities are subject to authorization from the Ministry of Sustainable Development, Environment, and Fight Against Climate Change (MELCC).
Since January 2014, cities are obliged to respect certain standards on the effluent of their wastewater treatment plants. These obligations are enacted by the MLECC and are issued at the same time as the certificate of authorization for the work. The discharge standards are constructed considering the environmental discharge objectives which, in turn, take into account the receiving environment. Since municipalities have the power to delegate the operation of the sewer system, it is important to specify that both the municipality and the operating company are fundamentally obliged to respect the discharge standards set by the MLECC. The company or municipality that fails to respect these standards or the sampling frequencies that have been prescribed may face financial and penal sanctions.
Connecting a customer to the sewer system
Once the terms and conditions of use of the sewer system are known, the business that chooses to discharge its effluent into the system is responsible for paying the costs associated with its connection. In addition to the payment of connection costs, a business wishing to connect to the local sewer system may be offered three agreement options. These include management through the issuance of a Certificate of Compliance at the start-up stage of a new project and at major modification stages, the issuance of a discharge permit, or the signing of a written contract regarding the terms and conditions of sewer service.
In addition to all of the above, the use of the local sewer system for the discharge of industrial effluent is subject to several other aspects. These include the funding of the system, which must be provided by the city, the power of inspection, which gives municipal officers the ability to inspect any property without notice, and the limit of liability of cities for damages.
Fortunately, there are more than just barriers associated with sewage spills. Cities also have the power to form a non-profit organization to provide technical support to businesses located within their jurisdiction. The creation of these organizations helps to fill the gap of in-house expertise in wastewater treatment for businesses.
Problems in local sewer networks
In times of rain or snowmelt, many municipalities have identified problems with missing or inadequate control basins. This problem can cause sudden surges in sewer lines, which sometimes leads municipalities to discharge raw water into the environment. When such a situation occurs, the person responsible must record it in a register and the data must be communicated to the Ministry on a monthly basis.
Secondly, the number of parameters monitored by the treatment plants is very limited and may overlook contaminants that should be more adequately monitored. The obligation of monitoring parameters by the different treatment plants is summarized as follows :
- Flow rate;
- pH ;
- MES ;
- DBO5C ;
- Total Phosphorus;
- Fecal coliforms ;
- Azote NH3-NH4 ;
- Acute toxicity testing.
Ammonia nitrogen analysis is only mandatory for plants that receive high concentrations of nitrogen. In addition, metals are only analyzed in the sludge of wastewater treatment plants. The repercussions caused by this weak monitoring requirement negatively impact the quality of effluents discharged by wastewater treatment plants.
Spill in nature
When a company chooses to discharge its effluents in the natural environment, it is subject to standards similar to those imposed on municipal water treatment plants. Since discharging effluent into the environment has adverse effects on ecosystems and human health, companies must incorporate a water treatment unit into their infrastructure that will perform the same function as a municipal treatment plant.
The effects of pollutant discharges to nature are manifested in three ways: discharges to surface water, discharges to land and discharges to the atmosphere. First, surface water discharges affect water quality and negatively impact fish populations. In addition, excessive contaminants can lead to beach closures and other restrictions on recreational water use, fishing and harvesting restrictions, and restrictions on the consumption of fish and shellfish. Liquid effluents discharged to surface waters may include decaying organic matter, phosphorus and nitrogen, chlorine compounds, bacteria, viruses, pathogens, metals, and many other substances such as pharmaceuticals.
Air emissions are related to volatile products such as methane, carbon dioxide, chlorine when used in a treatment process, hydrogen sulfide and many others. These products are released into the atmosphere during the collection or treatment of wastewater.
Finally, releases to land accumulate through the removal of organic and inorganic solids suspended in the wastewater. Inorganic or non-biodegradable debris is sent to landfills while organic debris is treated in a digester. Once the organic solids no longer produce methane, they can be used as fertilizer or soil conditioner, incinerated to produce energy, or landfilled.
Towards a better future
Knowing that water and the environment are very important to our survival, it is important to ensure their respect and sustainability. Several organizations have been created to promote compliance with standards, research and development and optimization of water use. Among these, the Canadian Water and Wastewater Association (CWWA) promotes standardization and compliance while advancing common interests, Environment and Climate Change Canada informs on hot environmental topics and CentrEau provides research and development. Of course, this list is only a taste of the many organizations that represent the interests of water, and we encourage all individuals and organizations to become aware of and support them.
Regardless of the type of industry operated or the type of discharge chosen, industrial effluents are a major challenge not only in Canada, but around the world. In Canada, we are fortunate to have standards and laws in place to ensure the respect of the environment and the safety of wildlife and humans. Fortunately, social dogmas are evolving and pushing companies to promote a more environmentally friendly future. Why not take advantage of this movement to do your part?
- Elsevier. (2018). Predicting wastewater treatment plant quality parameters using a novel hybrid linear-nonlinear methodology. Repéré à partir de https://www.sciencedirect.com/science/article/pii/S0301479719304505
- Gouvernement du Canada. (2017). Gestion des eaux usées. Repéré à partir de https://www.canada.ca/fr/environnement-changement-climatique/services/eaux-usees/gestion.html
- Gouvernement du Canada. (2014). Pollution issues des eaux usées. Repéré à partir de https://www.canada.ca/fr/environnement-changement-climatique/services/eaux-usees/pollution.html
- Voloshyn, K. (2014). Problématique de la gestion des eaux usées industrielles au niveau municipal dans les régions de l’Estrie et de la Montérégie. (Essai Université Sherbrooke)