Point sources vs non-point sources of pollution; how non-point sources of pollution can be controlled
One of the problems environmental scientists have been addressing, and which is common in many environments, is pollution. Pollution is any condition (chemical, physical, dissonance (noise), heat, etc.) in an environment that is at a level which can harm the health of living organisms, and distort the composition of non-living organisms. Activities or substances that cause pollution (i.e., pollutants) enter an environment through natural activities such as eruption of volcanoes, etc., and man-made activities such as combustion of gasoline and discharge of chemicals or solid waste into rivers and oceans, etc.
Disposal of waste, which can be categorized into point source (PS) and non-point source (NPS) types, leads to point and non-point sources of pollution. Point and non-point sources of pollution exist in environments as a result of the disposal of various types of waste by nature, human beings and animals. If points/areas of waste disposal are concentrated, then they lead to point source pollution. On the other hand, if points of disposal are not concentrated, then they lead to non-point source pollution. In summary, pollution is broadly categorized into two types: point source (PS) pollution and non-point source (NPS) pollution.
Point source (PS) pollution
Point source pollution is any individual identifiable point or concentrated area that emits pollution, such as a hole on a septic tank, or the open end of a pipe discharging wastewater from a brewery. Point source pollutants and pollution can be noticed in various industries: mining, agricultural, pharmaceutical, manufacturing, oil and gas, etc.
Examples of PS pollution in the agricultural industry include (but are not limited to) areas/points for feeding, collection of animal waste, distribution of fertilizers, storage of insecticides/pesticides, etc. Examples of PS pollution in municipalities include (but are not limited to) landfills, wastewater treatment facilities, underground tanks in petroleum stations, etc. It can be notice in these examples that pollutants can be traced to particular points or areas.
One major problem associated with PS pollution is that, whenever pollutants are not handled properly, they end up in surface water (rivers, oceans, seas, etc.), underground water, or even potable water supplies. These instances occur when pipes discharge wastewater from industries into rivers or groundwater environment. Another instance is when there are leakages in pipe networks (for potable water distribution) that allow polluted groundwater to mix with potable water flowing through them.
Non-point source (NPS) pollution
Non-point source pollution is any dispersed area of pollution that emits pollution which can’t be traced to an identifiable point, a single source, or a concentrated area. Non-point sources of pollution are often called “diffuse” pollution, which means that they’re sources of pollution that cover a wide area and can’t be traced to a particular point or concentrated area.
Examples of instances when NPS pollution occur: whenever rainwater carries fertilizers away from agricultural farmlands into rivers or water bodies; whenever underground water flows and carries pollutants (bacteria, harmful microorganisms, etc.) from a polluted area and deposits them in other areas that are either not polluted, or are less polluted; etc. Water that conveys pollutants may originate from man-made sources like irrigation systems and leaking pipe networks, or from natural sources like rainfall.
It is much easier and cheaper to identify and control/prevent pollution from PSs than from NPSs.
Negative effects of pollutants
Pollutants have a lot of negative impacts on living organisms, just to name a few: they can reduce the quality of air, land and water; they can damage health, create irritations (such as noise), and unpleasant tastes, smells and sights; etc.
Reasons why point sources are preferable to non-point sources of pollution
Point sources and non-point sources of pollution are two negatives—which if not handle properly, can degrade environments and make them unsustainable. Non-point sources of pollution are more difficult to handle, and have been known to degrade environments much more than point sources. In order to sustain environments much better, individuals and governments have to provide structures and enforce legislations that promote the use of PSs of disposal, and discourage the use of NPSs of disposal.
The major reason why point sources are preferable (in comparison with NPS) is due to the environmental benefits that PSs provide when compared with NPSs. In summary, these are the following reasons why point sources of disposal are preferable:
- Pollutants can be easily traced to PSs of disposal/pollution because PSs are usually noticeable, confined, and concentrations of pollutants are relatively easy to estimate. The point is this: appropriate technologies can be easily used to assess, control and abate pollution from PSs. On the hand, pollutants from NPSs are difficult to locate, and their concentrations are difficult to estimate because the pollutants are somewhat scattered and can’t be easily traced.
- Pollutants from PSs are more controllable, while pollutants from NPSs are less controllable because they can be easily transported and dispersed. In parts of the world where there are high humidity, environments have more NPSs of pollution, and are more susceptible to NPSs of pollution because they have more runoff (water/wastewater flow)—which means more transportation and dispersal of pollutants.
- It’s difficult to assess the origins and concentrations of pollutants transported from non-point sources into rivers and other bodies of water. Also, it’s a daunting task to conduct researches on NPSs of disposal/pollution than for PSs of disposal/pollution.
Generally, there are demanding challenges in studying different parameters associated with NPS disposal/pollution: determination of areas of selected sampling locations, determination of adequate runoff quality, determination of acceptable catchments, selection of the most acceptable test procedures, etc.
How to control non-point sources of pollution
In developing nations—particularly those that have low standards of living—prevention/control of NPSs of disposal and pollution has been quite difficult because it requires substantial amounts of money which are not always available. On the other hand, developed nations, which have higher standards of living, are able to control NPSs of disposal/pollution better by enforcing lawful regulations. For example, a regulation called “the Clean Water Act (1987)” was adopted in order to “establish a national program for controlling non-point source pollution and enhancing watershed protection”. Specifically, section 319 of the Clean Water Act adopts management programs for NPS pollution control.
Another control measure, as provided by Environmental Protection Agency (EPA), has been in place/practice since 1990. The EPA awards grants to states in order to assist in implementation of NPS control & management programs for reduction and prevention of NPSs of pollution.
Generally, non-point sources of pollution can be controlled by employing the following measures:
(1) Effective management of public lands
Public lands can be effectively managed in ways that reduce overflow of water, soil erosion, use of chemicals, etc. A lot of regulations (like erosion control laws) are in place, and people could be educated on watershed, conservation, and how to prevent NPSs of pollution in homes, offices, neighborhoods, industries, etc.
Homes are the smallest units in any society. A lot of activities that occur in (or around) homes require the use of best management practices (BMPs) for control/reduction of pollutants that contribute to NPS pollution. Each house contributes pollutants which can accumulate and create a significant impact on a neighborhood, city, state, nation, etc.
There are measures for pollution prevention that can be used to prevent NPS pollutants from littering around environments and mingling with storm water; such measures include: proper maintenance of sewerage systems; proper disposal of domestic animal waste; keeping food waste, cigarettes, etc., out of drainage systems so that clogging of can be prevented.
(2) Use of on-site technology in prevention or reduction of NPS pollution
Certain on-site technologies like stream-bank protection and channelization practices can be used to control or reduce NPSs of pollution which contain pollutants such as pesticides, fertilizers, animal dung washed away from farmlands, etc. These pollutants and similar types can be controlled by creating buffers consisting of vegetation, plants or trees between farmlands and banks of water bodies like rivers and lakes. Buffers help filter all types of pollutants—including sediments—and prevent them from entering receiving bodies of water, either completely, or, at least, to an appreciable extent.
Runoff from municipal and urban areas can be controlled using drainages, trenches and retention ponds to hold wastewater containing suspended solids and various types of pollutants.
(3) Use of watershed approach in management of NPSs of pollution
From available information, the watershed approach is proving to be the most effective technique for managing NPSs of pollution. A lot of literature has shown that every individual resides in a watershed or surface area in which water from many areas drains into. The watershed approach relies on input of information from local, state and federal agencies, and many stakeholders (political, social, and economic boundaries) who live in watersheds, and has been used to address serious environmental problems in watershed areas. The watershed approach has been successfully applied to a lot of watershed areas in the United States. According to the U.S. Geological Survey, U.S.A. can be divided into approximately 2,149 medium-sized watersheds, averaging about 1,700 square miles in each area.