Environmental Engineering Reference
In-Depth Information
1.
Depletion of the resource.
2.
Use of energy for pumping and potabilization.
3.
Treatment of wastewater effluents.
When surface water is not available, groundwater is a valuable resource. Unfortunately,
subterranean aquifers do not get recharged easily and if the rate of extraction exceeds the rate
of replenishment aquifers eventually dry out.
Pumping and treatment before water reaches the food-processing plant uses electricity,
which has associated indirect emissions, plus all the chemicals required for water purification.
In the same way, high water use produces elevated volumes of effluents that need treatment as
well. Regardless it is conducted in the processing facility or outsourced, the treatment of
wastewater is energy intensive with the current aerobic systems employed by the industry. In
addition, the treatment generates direct air emissions such as volatile organic carbon, ammo-
nia, methane, and nitrous oxide.
More on water and wastewater is covered in Chapter 9.
Solid waste
Solid wastes come from biological (e.g., peels, stems, rejects) and nonbiological sources such
as packaging material. When the biological waste has value, then is called a by-product and it
is used for other applications. However, low-value waste, for instance the rejects of a green
bean canning plant, are used as animal feed or sent to a landfill. Naturally, any method of
disposal of these waste materials has the associated impact of transportation.
Nonbiological waste is either transported to a landfill or incinerated in the plant. Both
methods have advantages and disadvantages. Incineration generates direct air pollution,
including particle matter, methane, carbon dioxide, and when chlorine compounds are pre-
sent, the formation of dioxins. Dioxins are a family of more than seventy-five related chemi-
cals that are detrimental for the environment and human heath. Landfill disposal does not
have some of the problems of incineration, but it requires transportation (sometimes long
distances) with the related emissions from diesel trucks, and in addition the associated impact
of land use.
Chemicals used in cleaning and sanitation
Cleaning and sanitation are daily routines for all food-processing facilities to avoid the
development of harmful bacteria that can compromise safety of the food products. Cleaning
requires the use of cleaning agents, which in most cases contain phosphate-based surfactants,
which after use are carried away by wastewater. During treatment most phosphates go
unchanged through the process and end up in rivers and lakes. The discharge of phosphates in
bodies of water promotes the development of unwanted aquatic vegetation (e.g., algal blooms)
which otherwise is kept at bay by the low levels of phosphate and nitrogen present in uncon-
taminated rives and lakes.
After cleaning, the application of sanitizers reduces the microbial contamination to levels
considered safe from the public health standpoint. Also, sanitation can be performed by
application of heat or other physical methods.
The most widespread sanitation chemicals are chlorine-, iodine-, and bromine-based
compounds, quaternary ammonium salts, and acids. At the levels used as sanitizers, these
compounds have a low environmental toxicity; however, the cumulative effect resulting
