Seaweeds: A Promising Source for Sustainable Development - Environmental Sustainability: Role of Green Technologies - page 82

vicinity of discharge of domestic effl uent. The
use of Ulva sp. as biofi lters has been suggested as
an effi cient method to recover large amount of
dissolved inorganic nitrogen (Vandermeulen and
Gordin 1990 ). Some seaweeds are used to remove
heavy metals to clean up wastewater. Milled,
dried species of the brown seaweeds Ecklonia ,
Macrocystis , and Laminaria were able to adsorb
Cu, Zn, and Cd ions from the solution. In another
laboratory-scale trial, Ecklonia maxima , Lessonia
fl avicans , and Durvillaea potatorum adsorbed
Cu, Ni, Pb, Zn, and Cd ions, though to varying
extents depending on the seaweed type and metal
ion concentration. After the extraction of alginate
from brown seaweeds, there is an insoluble waste
product, mostly cellulose, and the adsorbing
properties of this have been tested and found to
equal some of the brown seaweeds. Using such a
waste material is obviously more attractive than
using the dried seaweed itself. Another waste
product, from the production of Kelpak, and
liquid fertilizer previously mentioned, has also
been tested and found that it adsorbs Cu, Cd, and
Zn just as effectively as the seaweed from which
it is derived. So, there is the potential to use either
seaweed or residues remaining from seaweed
extraction. It is a matter of whether this is the
most economical way to do so, depending on
their availability and cost at the source of the
wastewater (McHugh 2003 ). There are two main
areas where seaweeds have the potential for use
in wastewater treatment. The fi rst is the treatment
of sewage and some agricultural wastes to reduce
the total nitrogen- and phosphorus-containing
compounds before the release of these treated
waters into rivers or oceans. The second is for the
removal of toxic metals from industrial wastewater.

originate from pond fertilization, feed, and
metabolic residues of the cultivated animals. In
this sense, the major challenge has been to
develop nonpolluting strategies that minimize the
negative effects of this activity. The most practi-
cal and economical approach to reduce the con-
centration of nutrients in aquaculture areas is to
treat the effl uents before it reaches the sea.
A potentially feasible alternative is the biological
treatment of effl uents, using macroalgae for
nutrient removal (Chopin et al. 2001 ; Neori et al.
2004 ). Heavy metals like Fe, Zn, Ca, and Mg
have been reported to be of bio-importance to man
and their daily medicinal and dietary allowances
(Duruibe et al. 2007 ). Even for those having bio-
importance, dietary intake has to be maintained
at regulatory limits, as excesses will result in
poisoning or toxicity, which is evident by certain
reported medicinal symptoms that are clinically
diagnosable (Fosmire 1990 ; Nolan 2003 ).
Methods for removing metal ions from aqueous
solution mainly consist of physical, chemical,
and biological technologies. Seaweeds are presented
as very good sorbents, because the cell wall of
green and brown algae contains alginate with
its carboxyl and hydroxyl groups (Davis et al.
2003 ; Vieira and Volesky 2000 ). Worse sorptive
properties are suggested for red algae owing to
its carrageen, exposing hydroxyl and sulfonate
groups (Tsezos and Volesky 1981 ).

12 Conclusions

Ecological and commercial seaweeds are impor-
tant as a potential source as food supplement in the
twenty-fi rst century because they serve as sources
of proteins, lipids, polysaccharides, minerals, vita-
mins, and enzymes. The use of seaweeds in the
development of pharmaceuticals, nutraceuticals,
and cosmetics and as source of pigments, bioac-
tive compounds, and antiviral agents is extensively
discussed. They are being used for food, medicine,
industry, and others such as integrated aquaculture
with fi shes, biofuel, and in removing the heavy
metal in cleaning wastewater. Hence, seaweeds are
the promising and versatile source for maintaining
green environment in a sustainable manner.

11.2 Treatment of Wastewater

to Reduce Nitrogen-
and Phosphorus-Containing
Compounds

The rapid expansion of aquaculture has contributed
to the excessive increase of nutrients, especially
nitrogen and phosphorous, in aquatic ecosystems
(Beveridge 1996 ). These nutrients generally