● `color{Brown}"Eutrophication"` is the natural aging of a lake by `color{Violet}"biological enrichment"` of its water.

● In a `color{Violet}"young lake"` the water is `color{Violet}"cold and clear"`, supporting little life.

● With time, streams draining into the lake introduce nutrients such as `color{Violet}"nitrogen and phosphorus"`, which encourage the growth of `color{Violet}"aquatic organisms"`.

● As the `color{Violet}"lake’s fertility increases"`, plant and animal life burgeons, and `color{Violet}"organic remains"` begin to be deposited on the lake bottom.

● Over the centuries, as `color{Violet}"silt and organic debris"` pile up, the lake grows `color{Violet}"shallower and warmer"`, with warm-water organisms supplanting those that thrive in a cold environment.

● `color{Violet}"Marsh plants"` take root in the shallows and begin to fill in the `color{Violet}"original lake basin"`.

● Eventually, the lake gives way to `color{Violet}"large masses"` of `color{Violet}"floating plants (bog)"`, finally converting into land.

● Depending on `color{Violet}"climate, size"` of the lake and other factors, the natural aging of a lake may span `color{Violet}"thousands of years"`.

● However, `color{Violet}"pollutants from man’s activities"` like effluents from the industries and homes can radically `color{Violet}"accelerate the aging"` process.

● This phenomenon has been called `color{Brown}"Cultural or"` `color{Brown}"Accelerated Eutrophication"`.

● During the past century, lakes in many parts of the earth have been `color{Violet}"severely eutrophied"` by sewage and
agricultural and industrial wastes.

● The prime contaminants are `color{Violet}"nitrates and phosphates"`, which act as `color{Violet}"plant nutrients"`.

● They `color{Violet}"overstimulate the growth"` of algae, causing `color{Violet}"unsightly scum"` and `color{Violet}"unpleasant odors"`, and robbing the water of `color{Violet}"dissolved oxygen"` vital to other aquatic life.

● At the same time, other pollutants flowing into a lake may `color{Violet}"poison"` whole `color{Violet}"populations of fish"`, whose decomposing remains further deplete the water’s `color{Violet}"dissolved oxygen content"`.

● In such fashion, a lake can literally `color{Violet}"choke to death"`.

● `color{Brown}"Heated (thermal) wastewaters"` flowing out of `color{Violet}"electricity-generating units"`, e.g., thermal power plants, constitute another important category of pollutants.

● Thermal wastewater eliminates or reduces the number of organisms `color{Violet}"sensitive to high temperature"`, and may enhance the growth of `color{Violet}"plants and fish"` in extremely cold areas but, only after causing damage to the `color{Violet}"indigenous flora and fauna"`.

● `color{Brown}"Wastewater"` including sewage can be treated in an `color{Violet}"integrated manner,"` by utilising a mix of `color{Violet}"artificial and natural"` processes.

`color{Green}"Arcata Marsh:"`

● An example of such an initiative is the `color{Violet}"town of Arcata"`, situated along the `color{Violet}"northern coast of California"`.

● Collaborating with biologists from the `color{Violet}"Humboldt State University"`, the townspeople created an `color{Brown}"integrated waste"` `color{Brown}"water treatment"` process within a natural system.

● The cleaning occurs in `color{Violet}"two stages"` –

(a) the `color{Violet}"conventional sedimentation"`, `color{Violet}"filtering"` and `color{Violet}"chlorine treatments"` are given.

● After this stage, lots of dangerous pollutants like `color{Violet}"dissolved heavy metals"` still remain.

● To combat this, an `color{Violet}"innovative approach"` was taken and

(b) the biologists developed a series of `color{Violet}"six connected marshes"` over 60 hectares of marshland.

● Appropriate `color{Violet}"plants, algae,"` `color{Violet}"fungi and bacteria"` were seeded into this area, which `color{Violet}"neutralise, absorb"` and `color{Violet}"assimilate"` the pollutants.

● Hence, as the `color{Violet}"water flows"` through the `color{Violet}"marshes"`, it gets purified naturally.

● The marshes also constitute a `color{Violet}"sanctuary"`, with a high level of biodiversity in the form of `color{Violet}"fishes, animals and birds"` that now reside there.

● A citizens group called `color{Violet}"Friends of the Arcata Marsh"` (`color{Violet}"FOAM"`) are responsible for the upkeep and safeguarding of this wonderful project. .

`color{Green}"EcoSan:"`

● All this time, we have assumed that `color{Violet}"removal of wastes"` `color{Violet}"requires water"`, i.e., the creation of sewage.

● But water is `color{Violet}"not always necessary"` to dispose off human waste, like `color{Violet}"excreta"`.

● Ecological sanitation is a `color{Violet}"sustainable system"` for handling human excreta, using `color{Violet}"dry composting toilets"`.

● This is a `color{Violet}"practical, hygienic"`, `color{Violet}"efficient"` and `color{Violet}"cost-effective"` solution to human waste disposal.

● The key point to note here is that with this `color{Violet}"composting method"`, human excreta can be recycled into a `color{Violet}"resource (as natural fertiliser)"`, which reduces the need for `color{Violet}"chemical fertilisers"`.

● There are working `color{Brown}"EcoSan toilets"` in many areas of `color{Violet}"Kerala and Sri Lanka"`.