Environmental Engineering Reference
In-Depth Information
Slurry disturbs aquatic ecosystems by increasing nitrogen and phosphorus levels, leading to the
growth of toxic algae, which poison the fish and decrease oxygen levels, causing fish to suffocate
(Smith et al. 1998).
32.2
Waste and WasteWater PollutIon
32.2.1 t
ypES
of
w
aStE
p
ollution
Increased use of agrochemicals, farm machinery, and irrigation in recent years has made the
pollution problem worse.
Milk spills (Nguyen 2000; Elmquist 2005; Filipy et al. 2006; Havlkova et al. 2008) are another
major environmental hazard for aquatic ecosystems. Milk is a highly polluting substance, and when
it gets into waterways, it is a threat to fish and other animals living within the waterway. This is
because the bacteria feeds on the milk and uses up oxygen that fish and other animals need to
survive. The dairy industry sometimes accidentally loses huge volumes of milk from its tankers.
Sometimes milk that cannot be sold is deliberately dumped and gets into waterways.
Chemicals used on farms, such as pesticides, fungicides, or fertilizers, are found in waterways
(Oturan et al. 2001; Guida et al. 2008; van den Berg and van Lamoen 2008). Common farm
chemicals include aluminum phosphide, cresol, organophosphorus pesticides, pyrethroids, methyl
bromide, strychnine, and tryquat. These chemicals are sprayed on farmland using tractors and boom
sprayers, or aerial sprays from light planes. Droplets are produced that can linger in air and may be
carried by wind away from the intended area. This is known as “spray drift.” Chemical spray drift
cannot always be contained and might still occur despite correct application. These chemical sprays
often drift over neighboring properties or waterways and can affect human health, animals, and
the environment (Muller et al. 1983; Chung et al. 1985; Fawcett 1991; Bicudo and Svoboda 1995;
Schierhout et al. 1997; Brewer et al. 1999; Cumby et al. 1999).
Factory-farmed animals are given antibiotics in their food to prevent infection in their overcrowded
conditions. Animal waste contains substantial amounts of bacteria, and because only about a quarter
of the antibiotic is digested by an animal, the waste may also contain antibiotics. This combination is
a perfect opportunity for the development of antibiotic-resistant bacteria which may pass to humans
when water or soil is contaminated with the bacteria from farm waste. Vegetables and fruit can also
become contaminated with antibiotic-resistant bacteria if animal waste that contains the bacteria is
spread onto agricultural fields of fruit or vegetables.
Many farmers in developing countries want to maintain traditional farming methods, which are
often better for the environment, but competition from corporations contributes to making these
unviable, forcing small farmers into large-scale farming or condemning them to poverty.
Permaculture (Wikipedia 2008c) and small-scale organic farming are better alternatives to
monocultures and factory farming. But these systems are still only models for farming and are
not being used. There is still a long way to go before agriculture as a whole is environmentally
sustainable.
We need more government controls on farming-related pollution and waste. There are measures
that can be taken to ensure that manure from farms is treated and does not reach waterways and
pollute them. There should be improvements in farm practices through an appropriate combination
of educating land owners and land managers, providing funds for improvement programs, offering
incentives and subsidies, improving regulations, and better enforcement of them.
Farm waste has huge potential as a source of energy (Cantrell et al. 2008; Lansing et al.
2008). It is a major source of methane, a greenhouse gas contributing to climate change. When
possible the methane should not be allowed to escape into the atmosphere. It should be captured
and the energy potential should be harnessed. Typical values of biogas potential are presented in
Table 32.1.
