Algae alleviates

Tanks containing spirulina: wa (Credit: Meera Iyer / CSE)HOUSING lower- and middle-class blacks,
certain South African townships are
seriously threatened by contamination
caused by human wastes. With no
sewage disposal system, the residents of
these poor localities use buckets to
excrete and once these are full to the
brim, the waste is either dumped into
streams or on the outskirts of the townships (ScientificAmericah, Vol 273, No'5).

The dumping of these wastes is
proving to be a major threat to the environment, as not only are the streams
affected by it but even groundwater
sources lying just four metres below the
surface are.being polluted. But help is
on the way. Peter D Rose of the Rhodes,
University in SouthAfrica is using an
algae-based system to solve the crisis. A
pilot plant constructed nearby will
receive the waste emitted by 500-1,000
people, through a 1,00,000 ha area of
ponds and channels filled with
spirulina. The single-celled plant thriving on salty, nutrient-rich sewage offers
solace to millions of helpless South.
Ilicans. When exposed to sunlight,
these plants seek higher dissolved oxygen levels and ingest most of the waste,
and the remaining heavy metals and
inorganic detritus settle at the bottom of
the waterbodies.

Sewage processing by algae, an age-old method, is now being made more
effective by advanced technologies. In
the past 10 years researchers have concentrated on cultivating algal species
which can do even bitter than the activated-sludge process practised by
industrialised nations. The algal ponds
do not require the equipment and
power needed to run the conventional
activated-sludge ponds. This reduces
the building and operation costs by
about a half. These plants do not consume much water, which is an important innovation for and South Africa.
The resultant sludge produced is also
lesser in quantity, making it easier to
truck it down to landfill sites. Not only
that, but most of the sludge is usually
tonnes of dead algae, which once dried,
makes good fertiliser and,fish-food
additive. Another *advantage of algal
ponds is that they do not stink, as the
algae only produce a lot of oxygen and
not other rotten smelling gases.

For Rose, the technology serves a
dual purpose. It holds the potential for
improving community sanitation and at
a low cost, making it attractive to the
needs of developing countries., "One of
the future benefits of the process is that
once you have this algal biomass, you
might be able to engineer it to produce by-products that are more valuable than
animal feeds," he says. His team
recently studied another algae,
Dunaliella salina, which when exposed
to excessive salt or heat, produces large
amounts of beta-carotene (a nutrient
used by the body to make vitamin A).

Rose has also demonstrated the usefulness of the system in treating industrial waste, from tanneries. Tannery
waste includes effluents like sulphides,
ammonia and heavy metals, which not
only give off bad odour but are also
among the most dangerous pollutants
to be emitted by any industry. Rose tried
out the spirulina treatment on this
waste, when he noticed that the plant
flourished in a tannery's evaporation
pond. The treatment systems tried out
in Transvaal, Namibia and Cape Town
tanneries show promise, as they have
been successful in squelching odour and
reclaiming water lost through evaporation. With the expected expansion in
the tanning industry in South Africa,
the algal-pond system is expected to be a
major boon to the country.

Says Rose, "Rapid industrialisation
in the Third World often happens at the
expense of the environment, because
the costs of First World technologies to
remedy the situation cannot be borne
simultaneously. To come up with a low-
cost solution that results in something
not just safe but useful - well, that is
the first prize in biotechnology."