Dr Anjani Ganase reminds us that what drains from our islands ends up in the sea. How do we ensure that we do not enrich the coastal waters with chemicals and pollutants from agriculture, manufacturing and yes, household use.

All drains lead to the ocean, but do we think about this when we wash our cars, do our laundry, clean our dishes? Nutrient pollution is caused by the nitrates and phosphate compounds that flush into rivers and coastal marine environment from the use of agricultural fertilisers, discharge of high volumes of greywater, and industrial effluent.

Nutrient pollution is a growing issue impacting our waterways and the ocean with unforeseen consequences. At the global scale it is rapidly becoming a major concern given the many other large-scale issues that are plaguing regions of the world. Most noticeably, in the Caribbean we see the rise of sargassum blooms in the southern Atlantic, the presence of harmful algal blooms in the northern Caribbean and the expansion of dead or hypoxic zones that are uninhabitable.

Start in the home

While the lack of regulation in the use of fertilisers in agriculture and industrial effluent are major issues, what is often overlooked are the domestic discharges of large volumes of nutrient rich grey water from households directly into our country’s freshwater systems.

Grey water is any type of water that is discharged from a household other than sewage (aka black water). It is made up of a relatively high volume of water contaminated with nutrients along with other physical, chemical and even biological pollutants. The average Trinidadian household uses and therefore disposes of up to 82 gallons of water per day from cleaning, dishwashing, laundry, showers, cleaning the car and the yard. The used grey water is disposed directly into the surroundings via the street drains which then run into our rivers and streams that flow to the ocean.

Making up chemical pollutants and nutrients, here are some of what goes out in wastewater: nitrates, phosphates, ammonia compounds, other synthetic organic compounds used for cleaning, physical contaminants of plastics, cloth fibres, particulates, food scraps, grease and other organic matters. Biological contaminants include bacteria and protozoa, some of which are pathogenic like E. coli and salmonella.

[caption id="attachment_1156333" align="alignnone" width="1024"] Sargassum along Tobago’s Caribbean coast. - Photo by Anjani Ganase[/caption]

If a single household uses up to 82 gallons a day and most is discharged as greywater, let’s imagine the discharge quantities of say the Diego Martin Borough or the communities that surround the Maraval River or south-west Tobago. This results in highly polluted discharges, yet it is the norm in many places for household drains to pipe directly into storm drains and rivers.

What does this do to the river ecosystems?

The discharge of greywater into rivers damages river ecosystems through resulting algal blooms or eutrophication. High organic matter breakdown can cause microbial b