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Water Pollution and Treatment

Water Pollution


A trend towards large-scale agricultural and livestock production the last few decades has increased the pressures on environmental resources and has contributed to the contamination of surrounding water supplies throughout Canada (Nolet, 1999). In Quebec, four watersheds dominated by the intensive production of cash crops and by intensive hog production also contain the most polluted rivers in the province (FPCCQ, 1999).  The poor water quality found in these regions is partially the result of agricultural practices such as improper manure spreading, the increased use of chemical fertilizers and pesticides, and the lack of soil conservation practices which contribute to diffuse pollution (BAPE, 2000). While the deterioration of water quality is linked to the intensification of both the agricultural and livestock industry, there is no direct causal relationship between the size of hog production facilities and the magnitude of water pollution produced. Nevertheless, the complexity of managing manure surpluses and monoculture fields tends to increase as the size and intensity of industry increases, which may have direct implications for water contamination (Fraser, 1985).

To understand the importance of large-scale hog production on water pollution, we analyzed both direct and indirect sources of pollution. In addition, we investigated the different sources of pollution associated with livestock production, including the production of animal feed, and the relative contribution of large-scale hog production practices to water pollution. Thus, the pollution of water by the hog industry is not restricted to pollution from manure alone, but includes pollution that is emitted through crop production as well. Furthermore, the hog farms are often located in agricultural regions that include other types of livestock production and/or other agricultural industries that complicate attempts to isolate and quantify the pollution.

Direct sources of pollution from the hog industry include manure and nutrient volatilization from waste storage facilities. While the provincial Regulation for the Reduction of Pollution of Agricultural Origin (Bolinder et al., 1998) requires the installation of covered, water-tight manure storage facilities, only 90% of hog producers have adequate storage facilities (Enright, pers. comm., 2000). Even with clay liners, lagoons allow waste to leach into the ground.  Since lagoon specifications allow leakage through the clay liners at a rate up to 0.036 inches per day, at the maximum allowable rate, a three acre lagoon could legally leak more than a million gallons a year (Weida, 2000). To a lesser extent, ammonia volatilization, a process by which nitrogen from the open waste lagoons is transformed into gaseous forms and enters the atmosphere, can contribute to water pollution when it is deposited in the landscape (Gangbazo, 1984). However, as most lagoon systems are now covered according to regulation, pollution in agricultural landscapes from nitrogen deposition has decreased.

It is difficult to determine how much water pollution could originate from the hog industry, so we examined characteristics of the hog industry to assess whether the risk of pollution was higher from hog farms than other agricultural operations.  First, in order to remain competitive industrial hog producers increase the size of operations by increasing animal confinement and by improving feed quality (Enright, pers. comm., 2000).  However, these measures may increase the amount of manure produced per animal and change its composition (Fraser, 1985). The larger volume of animal manure in areas with increased numbers of hogs requires more land for manure storage and disposal (Fraser, 1985). Due to the expense involved in purchasing extra land, hog producers have tended to over apply manure to dispose of excess manure (Enright, pers. comm., 2000). Subsequently, the environmental impact of hog production would be reduced if agricultural production zones were less concentrated but the difficulty involved in getting permits for new facilities outside these zones encourages producers to concentrate (Enright, pers. comm., 2000).

In addition to problems related to intensification, are those related to the inherent characteristics of the hog manure that increase nitrogen and phosphorous contamination. First of all, many hog producers in Quebec use liquid manure handling systems, and the nitrogen in liquid manure is generally more readily available to the plants than the nitrogen in solid manure. As a result, the nitrogen is more likely to be lost to the environment through leaching (Enright, pers. comm., 2000). Furthermore, compared to other livestock manure, hog manure contains one of the lowest nitrogen to phosphorous ratios (Fraser, 1985). Since plants generally require two to three times more nitrogen than phosphorous, soils fertilized by hog manure can become saturated with phosphorous (Donham, 1995). The increased input of phosphorous onto soils, coupled with the limited capacity of some soils to retain phosphorous, increases the risk of phosphorous contamination of surface water. Problems related to phosphorous runoff include eutrophication; overgrowth of algae and aquatic plants; reduced oxygen levels in water; and subsequent changes in the species composition of the aquatic ecosystem (Bolinder et al., 1998). In response to problems associated with phosphorous contamination, the UPA (Union des Producteurs Agricoles) now recommend that wastes be spread according to the amount of phosphorous required by the crops, instead of by the amount the nitrogen (BAPE, 2000).

The limited amount of land available for hog producers to spread manure results in the preferential production of corn for hog feed due to its high nitrogen requirements, which allow for the highest rate of manure application per hectare. The recommendations for crops like wheat, barley, oats and canola range from 40 to 90 kg N/ha, whereas the corn recommendation is 120 to 170 kg N/ha, and most producers put on 150 to 200 kg N/ha to ensure a maximum yield (CPVQ, 1996). Despite the high nitrogen requirement of corn, the crop has poor root systems that prevent it from absorbing all nutrients in the manure (Moore, pers. comm., 2000), resulting in a greater potential for nitrogen losses.

Corn production also contributes to water contamination through the use of herbicides to remove weeds. Corn producers are the primary consumers of herbicides, and spray 94% of the fields under cultivation (FPCCQ, 1999). Accordingly, high pesticide contamination risks are found in Lanaudiere, Monteregie-Est and Monteregie-Ouest, which are regions dominated by corn crop production (Table 4). There are currently incentives being developed to prevent pesticides from reaching the water table due to the presence of significant amounts of pesticides in water (FPCCQ, 1999).

Corn production is also associated with herbicides, and heavy use in the past has resulted in the resistance of the crop to some herbicides (Gingras et al., 2000). Compared with other types of agricultural production, St-Laurent Vision (2000) confirmed that corn production is mainly responsible for herbicides leaching into surface and ground water (Giroux, 1998).  At the present time, atrazine and metolachlor are the two corn herbicides that are found most often in rivers. Of the two, atrazine has been measured above regulation levels suitable for aquatic life and drinking water (Gingras et al., 2000) in many regions associated with heavy corn crop production (FPCCQ, 1999).

Further complications associated with intensive corn production relate to fertilizer application. Although the Quebec Regulation for the Reduction of Pollution of Agricultural Origin prohibits the application of manure between October 1st and March 31st (Bolinder et al., 1998), the restrictions do not account for climate and soil variability that may allow for less than ideal conditions at the time of application. Since corn producers are discouraged in applying manure during the summer, their fields are fertilized either before seeding or after harvest when the soil is often too damp and the nutrients are not yet required (BAPE, 2000). Consequently, corn production induces soil and field management problems, leading to soil compaction, soil erosion, and over fertilization (Enright, pers. comm., 2000). 

To avoid over fertilisation of any farm, waste surpluses need to be reallocated to avoid adverse effects to the environment. Since this involves transporting the manure to other locations at high costs, this practice is not widely performed. In fact, only 10% of cropping industries in Quebec currently accept manure from other industries which indicates there is a high potential for spreading excess manure on other areas, thus reducing the stress in regions of concentrated agricultural practices (FPCCQ, 1999). The nutrient surplus resulted in the formation of the Plan Agro-Environnementaux du Quebec (PAEF), new legislation that requires the installation of cooperatives to allocate surplus manure (BAPE, 2000). Mandatory for all farms by 2004, the new legislation also restricts farmers in the amount of fertilizer that can be applied, as well as the time of its application. Despite this potential solution, mineral fertilizers are being applied to maximize output in certain areas even though nutrient surpluses are observed throughout the province (FPCCQ, 1999).

Hog manure characteristics and land use in agricultural regions occupied by large numbers of hog producers have contributed to higher nutrient surpluses in hog-dominated regions than regions occupied by any other agricultural activities (FPCCQ, 1999).  On average, regions in Quebec containing hog farms have almost four times as much nitrogen (Figure 2) and almost twice as much phosphorous per hectare in comparison to regions without hogs (Figure 3).


Figure 2: Amount of nitrogen (Kg/ha) on land cultivated by other agricultural industries and on land occupied by the hog industry for thirteen regions in Quebec (FPCCQ, 1999). Note: Region listed as Saguenay Lac St. Jean region includes Cote Nord and Nord du Quebec.


Figure 3: Amount of phosphorous (Kg/ha) on land cultivated by other agricultural industries and on land occupied by the hog industry for thirteen regions in Quebec (FPCCQ, 1999). Note: Region listed as Saguenay Lac St. Jean region includes Cote Nord and Nord du Quebec.

The risk of contamination by nitrogen, phosphorous and pesticide pollution in the agricultural regions of Quebec was assessed (Table 4). Of these thirteen regions, seven had high to very high risks of diffuse phosphorous pollution attributed to over fertilization (FPCCQ, 1999). In addition, three regions were at high risk for diffuse nitrogen pollution, which were assessed from data regarding nitrogen application, volatilization during manure spreading, soil conservation practices, drainage, crop type, and runoff potentials (FPCCQ, 1999).

Table 4: Risks of point source pollution and diffuse pollution for 13 regions in Quebec, including data regarding the presence of cash crop production in the regions. Note: L=low risk; M=moderate risk; H=high risk; VH=very high risk. 1Saguenay-Lac-St-Jean region includes Cote-Nord and Nord-du-Quebec (FPCCQ, 1999).




Cash Crop Production

Risk of Point Source Pollution

Risk of Diffuse Pollution

N and P





Abitibi- Temiscamingue No H M M M M
Bas-St-Laurent No H M M M M
Centre-du-Quebec Yes M M M H M
Chaudiere-Appalaches No H M L to M M E
Estrie No M M L H M
Lanaudiere Yes M M H VH H
Laurentides Yes M L M H M
Mauricie Yes M M M H M
Monteregie-Est Yes H M H H H
Monteregie-Ouest Yes H M H H H
Outaouais No M L L M M
Quebec No M L M M M
Saguenay-Lac-St-Jean1 No M M M M M

The six regions with high to very high risk of either nitrogen or phosphorous contamination are also dominated by cash crop agriculture.  The risk of water contamination is higher in these regions due to widespread use of conventional rather than conservation tillage practices (FPCCQ, 1999). For example, in the Lanaudiere region, where annual crops account for 70% of cropping area, only 8% of the area practices soil conservation techniques (FPCCQ, 1999). Furthermore, six of these high risk regions including the Centre-du-Quebec, Laurentide, Mauricie, Monteregie Est and Monteregie-Ouest, also contain intensive hog production industries.

In addition to contamination of surface water, studies across Quebec show that around 40% of private wells are contaminated with nitrates, pesticides or microbes emitted by the agricultural industry (MSSSQ, 1996). However, it is difficult to determine what type of industry is responsible for the pollution. This is partly due to the lack of data and hydrogeologic maps of ground water processes such as aquifer vulnerability, recharge, and quality (BAPE, 2000).  While independent and fragmented studies do exist for some areas, this information has not been synthesised. Consequently, information regarding well-water quality is derived primarily from well drillers.  At present, no policy exists for ground water quality control, but regulations for well water control may be passed by March 2001, and will require new home owners to test water for contamination (Ouellet, pers. comm., 2000).

Water Treatment


Environment Canada (2000) estimates that the limited capacity of our lakes, rivers and ocean to treat the wastes that enter our water is costing us billions and billions of dollars to clean up or to prevent. Practices associated with industrial hog production, including intensive feed crop production, inputs of manure, fertilizer, pesticides and herbicides, contribute to the contamination of water. Water must be treated by municipal water treatment facilities before it is suitable for human consumption. However, it is generally difficult to attribute the cost of water treatment to only one industry because of problems associated with determining the source of pollutants in concentrated production zones (Massicott, pers. comm., 2000).

To quantify the cost of water treatment, we compared treatment costs of two municipalities that use the same technology but take their water supply from either a highly polluted river or a clean river. Differences in the size of treatment facilities, workers employed and amount of water treated make it difficult to compare overall treatment costs (Massicott, pers. comm., 2000). Therefore, we examined the cost difference of products used to treat water in two municipalities, which include coal, ozone, sand, chlorine and the coagulant alum sulphate (Sauvageau, pers. comm., 2000).

The two municipalities chosen are L’Assomption, which treats water from the heavily polluted Assomption River and St. Lambert, which treats a relatively clean section of the St. Lawrence River. The L’Assomption region is an ideal site for this analysis because it is located in a region of concentrated hog farms (Sauvageau, pers. comm., 2000). It is likely that the hog industry contributes to pollution in this watershed because the industry accounts for 52% of the animal production and 31% of the corn production in the area (SLV, 2000). From Table 5, the cost of water treatment products in the L’Assomption region is four times the cost required for St. Lambert water. This comparison provides a general estimate of some of the costs associated with water treatment in agricultural areas concentrated by hog farms.

Table 5: Cost of water treatment products per 1000 m3 for L’Assomption and St. Lambert regions in Quebec.


River Treated

Level of Pollution

Number of Products Used

Cost of Treatment ($/1000 m3)

L’Assomption L’Assomption




St. Lambert St. Lawrence