Environmental Engineering Reference
In-Depth Information
typically causes vomiting, esophageal and abdominal pain, and bloody
“rice water” diarrhea [29]. Environmental toxins enter the food chain
through irrigation water.
3.1.4 Technologies
A variety of methods have been used for the fast removal of arsenic in
water and wastewater, some of which are discussed below.
3.1.4.1 Oxidation/Precipitation
Oxidation/precipitation is a simple, slow process using low-cost materials.
It also oxidizes other inorganic and organic constituents in water. It kills
microbes and oxidizes other impurities [30-36], while mainly by oxidation
alone, As(V) can be removed and the, oxidation process can be accelerated.
Oxidation steps and ei cient control of pH is needed for this method.
3.1.4.2 Coagulation/Electrocoagulation/Co-precipitation [37-39]
In the alum coagulation process durable powdery chemicals are available.
It is a low-cost technology that is very simple to operate, and is very ef ec-
tive over a wide pH range. In iron coagulation and lime sot ening, very
common chemicals are used which are easily available and more ei cient
than alum coagulation on a weight basis. In contrast, it produces toxic
sludge, low removal of arsenic occurs and pre-oxidation may be required.
Also, readjustment of pH is required for this process.
3.1.4.3
Sorption and Ion Exchange Technique [40-43]
Activated alumina, iron-coated sand and ion exchange resin are very cheap
and do not require regeneration. h is technique removes both As(III) and
As(V) and is pH independent. Also, it is relatively well known and com-
mercially available. Beside all this, in this technique replacement of mate-
rial at er four to i ve regenerations is essential. It produces toxic solid waste.
It is a high cost medium and high tech operation.
3.1.4.4
Membrane Technologies [44-51]
h ese techniques are well-dei ned and have high-removal ei ciency and
produce no toxic solid waste. h ey are also capable of removing other con-
taminants. But similar to other techniques, they also have some disadvan-
tages like very high capital and running costs, pre-conditioning, and high
water rejection.
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