Where Water Pollution Comes From
The two most common ways for water pollution to occur is for the pollutants to be dumped directly into the water (commonly referred to as "point sources") and for pollutants to be picked up off the ground by rain water that then carries the pollutant into a nearby body of water (cleverly referred to as a "non-point source").
Point Sources -
Point sources are when a factory or a wastewater treatment plant dumps treated (or untreated) wastewater into a body of water, usually a river or ocean. For the last 30 years or so, point sources have been heavily regulated and so not too much pollution comes from point sources (though there are exceptions). Point sources are usually required to have a permit, and are given certain standards that their wastewater must meet. These standards come with requirements for testing, reporting and inspections. Violations can require new investment in treatment technology, fines or both.
Non-point Sources -
The trouble with non-point sources is that the pollutants can come from anywhere, which makes it very hard to regulate and treat. Here is how it can happen: you come out one day and notice a small oil spot underneath your car. So you take your car to get the leak repaired - meanwhile, it rains. In most cases, that means the rainwater that hits your driveway picks up some of the oil and carries it along. If that rain water happens to cross some green space (like a lawn or other grassy area) it is possible that the plants will strip the oil out of the rain water as the rain water sinks into the ground. But, if there is no grassy area, or if the ground is super saturated, that rain water will probably make it into a river, carrying the oil with it. Now imagine that happening in thousands of places all over town - the final impact is felt downstream when all of that pollution finally makes it to the river. As you can see, this is a tough problem.
Other -
There are, of course, other ways for pollution to enter bodies of water. One is the rain itself, if that rain is already carrying the pollution. Most of us who grew up in the '80s remember the issue of the day - acid rain! Power plants discharge pollution that turns into sulfuric acid or nitric acid. When the acid is carried by the weather, it can then rain down into a body of water - enough acid rain can change the pH of the water (especially in a small lake) which can have devastating effects on the animals that live in the water. Because of action taken to clean up power plant emissions, acid rain is less of a problem than it was, but it still exists.
Another example is when the wind picks up pieces of garbage and carries that into a body of water (heavy rains can do the same). Plastic trash can float on the water, and sometimes resembles food to certain animals. The animals eat the plastic, which causes problems with their digestive system and the animals die. An extreme example of this is the "Great Garbage Patch" that sits out in the Pacific Ocean.
Water Pollution Named -
Generally speaking, pollutants in water do one of two things - make the water unfit for drinking; or make the water unfit for fish and other aquatic creatures.
No Drinky!
There are a lot of substances that you don't want to put in your body. Some are chemicals and others are metals. In very tiny quantities, they probably won't do much harm. But in larger amounts they can cause damage to parts of the body (like the liver or kidneys) or cause cancer. There are standards for a lot of different substances, and the government can add or remove substances as science shows that a specific substance is harmful.
One of the issues is that some of these substances are bioaccumulative. This means that the substance will build up in your body until it reaches harmful levels. Examples of this are lead and mercury - these metals can build up inside your body until they reach a point that they do harm. The smaller a person is (like a child) the smaller the amounts they can tolerate. Bioaccumulation is the reason that certain fish have warnings - large predator fish can accumulate significant amounts of various substances in their bodies, which get passed along to anyone who eats them.
Where did the fish go?
Other pollutants make the water harmful to fish and other aquatic critters.
pH - if water is either too acidic, or too basic, critters can't live in the water. For example, you may hear about ocean acidification - as the pH of the ocean moves toward the acid side, it makes it more difficult for colar to grow. The acidic water literally eats away at the coral shell and kills of the creatures that make the coral. See wikipedia's article for more info.
Organics - anyone who has had a backyard pool has dealt with organics. What happens is that organic matter gets into the water. And when enough organic matter gets into the water, critters begin to grow. All by itself the critters (sometimes algae) aren't a problem. The issue is when a lot of critters grow all at once - in order for the critter to break down the organics in the water the critter has to pull oxygen out of the water. If too much oxygen is pulled out of the water, then the fish don't have enough oxygen to survive. And when the critters die and sink to the bottom, the microorganisms that decompose the critters pull oxygen out of the water as well. One example of this is the so called "Dead Zone" that exists around the delta of the Mississippi river - too many nutrients in the water lead to critter growth (and death) and low oxygen.
Solids - particles of sand and other solid materials can get into water. These particles can deposit in slow moving areas, building up sediment. This can cause issues with water flow, potentially cutting off some areas of a river, which can disrupt the movement of fish and other aquatic animals.
What Can We Do?Fortunately, everyone can help reduce water pollution! Here are some simple ways:
Reduce - Simply by reducing the amount of wastewater we create, we can help reduce water pollution. The less wastewater that is sent to the sewer, the less that has to be treated. If you live in a large city, the sewer system may be at capacity - too much water sent to the treatment plant results in untreated or partially treated water being dumped.
Use chemicals with care - Any chemical that you apply to your garden or lawn (weed killers, fertilizers, insecticides) can be washed away by rain and into a nearby river. If you are going to use these chemicals, the key is to apply them in the correct amounts and to make sure that you don't apply them right before a mjaor storm. You can also change your landscape so that you don't have to use the chemicals, or find natural treatments for pests (did you know you can use beer to kill slugs?).
Proper car care - keeping your vehicle leak free is another way to combat pollution. Make sure that leaks are repaired and clean up large spills of any car fluids quickly. And if you are going to wash your car, it may be better to go to the coin wash down the street than do it in your driveway. Many newer car washes are required to recycled and/or treat their wastewater, which keeps the soaps and waxes out of the water.
We all need water to live, thrive and survive - so let's take care and keep our water clean!
