Most people do not think much about what we put down the drains. Once whatever we have put down the drain is out of sight it is usually out of mind. While we would not litter our surroundings or dump potentially harmful contaminants into nature, many do not think twice before discarding environmentally damaging substances down the drain. In modern societies, such substances can be found in everyday products and may contaminate your wastewater more than you think. While our drains are being subject to an abundance of potentially harmful substances, the wastewater treatment centres are not equipped to adequately treat the wastewater. The unfortunate result is contaminated wastewater being released back into nature, with significant environmental impacts.

What is Wastewater?

Wastewater, or liquid waste, is any waste material in a liquid form. Domestically, this usually refers to the used water that is a result of everyday activities in households. This type of wastewater can be divided into two categories: blackwater and greywater.


Blackwater, commonly known as sewage, is wastewater from toilets that contains urine, feces, toilet paper, flush water and everything else we flush down our toilets.


Greywater is wastewater from domestic appliances other than toilets, such as sinks, bathtubs, showers, dishwashers and washing machines.

What Happens to Wastewater?

Most households in Europe are connected to a sewage system and a wastewater treatment plant. The wastewater that enters our drains enters these sewage systems before being transported to treatment plants. Here, the wastewater undergoes extensive treatment to remove contaminants before being discharged back into lakes, rivers or the ocean. In some societies, greywater is recycled for non-drinking purposes, such as for irrigation, which refers to watering of plants and landscapes (excluding edible crops) or for flushing toilets, while the organic solids remaining, so called “sewage sludge” is recovered for energy production.

A wastewater treatment plant located next to a river in green surroundings
Domestic wastewater is treated at a wastewater treatment plant before being released into nature. 📷 by Franz W. / Pixabay 

Wastewater Treatment Process

The wastewater treatment process generally has three stages: primary, secondary and tertiary treatment.

Primary Wastewater Treatment

In the first stage, solids are separated from the wastewater. This is done by temporarily holding the wastewater in a large settlement tank until the heavy solids, also called “sewage sludge” sink to the bottom and the lighter solids, such as grease and oils, float to the surface. These solids are then removed from the wastewater.

Secondary Wastewater Treatment

In the second stage, dissolved and suspended organic matter that escaped the primary treatment are broken down. This is a natural process that is achieved by pumping air into the wastewater and adding small amounts of sludge, known as “seed sludge” to promote the growth of microorganisms and bacteria which digest the remaining organic matter.

Tertiary Wastewater Treatment

In the third stage, the impurities are removed from the wastewater before it is recycled or discharged into the environment. Up to 99% of the impurities are eliminated during this stage. This is achieved through various chemical and/or physical treatments.

Environmental Impact of Wastewater

Despite the high rates of treated wastewater in Europe, much of the wastewater is inadequately treated before being released back into nature. Treated wastewater from modern households often contain potentially harmful contaminants originating from sources like pharmaceuticals, cleaning agents, food additives, cosmetics and personal care products. While the majority of these contaminants are removed from the wastewater in treatment plants before it is released back into nature, low concentrations remain and these are frequently detected in treated wastewater. When inadequately treated wastewater re-enters ecosystems, it can have significant environmental impacts. Chemical contamination, antibiotic resistance, eutrophication and microplastic-pollution of natural environments are rising concerns our developed societies are facing today.

Treated wastewater poring back into the sea
Treated wastewater being released back into nature. 📷 by Andrew Martin / Pixabay 

Chemical Contamination

Most people fill their homes with products containing potentially harmful chemicals. These are not only found in harsh cleaning products, but also in many of your everyday products, such as in personal care products and cosmetics. When these chemicals escape treatment and accumulate in nature they can over time contaminate surface water, groundwater and soil, causing adverse long-term effects for natural habitats and their inhabitants as well as for humans. The abundance of different chemicals that enter nature through treated wastewater is additionally subject to the cocktail-effect, which is the notion that mixing different chemicals might alter their effect and make them more toxic.

Antibiotic Resistance

Traces of pharmaceuticals, such as antibiotics and ibuprofen and other antimicrobial agents commonly present in personal care products, have been found to frequently enter the environment through treated wastewater. The presence of such contaminants raises a concern of antibiotic resistance, in which bacteria become antibiotic-resistant, and the long-term health implications this has for humans and animals.


Many personal care and cleaning products also contain high levels of plant nutrients, such as nitrogen and phosphorus, which often remain in the treated wastewater that is released back into nature. These nutrients impose a threat to ecosystems because they cause eutrophication if accumulated in waterways. Eutrophication refers to bodies of water that are overly enriched with nutrients. It causes structural changes and imbalances in ecosystems, such as excessive growth of algae and plankton, biodiversity loss, species composition changes, growing dead zones and lowered water quality.


Treated wastewater is considered a key source of microplastic and microbeads as wastewater treatment plants are inefficient at filtering them out. These small plastic fibres enter our wastewater through the washing of synthetic clothes, and through many personal care products and cosmetics that ultimately ends up in the drain. Once the inadequately treated wastewater is released into the environment, these chemical-leached particles frequently enter the food chain as they are often ingested by various land- and water-based species. The microplastic can physically damage the organs of these creatures, while leaching out toxic chemicals, causing hormone disturbances, reduced immune function and reduced reproduction abilities. Both the microplastics and the chemicals may make their way up the food chain, potentially affecting whole ecosystems.

How to Prevent Harmful Wastewater?

So how do we put a stop to all this potentially harmful wastewater entering the environment? There are two important ways we as individuals can mitigate the harmful impact of wastewater; by reducing our water consumption and by using organic products.

Number 1 Reduce Water Consumption

Reduce and better control your water consumption. By using less water, you will produce less wastewater, which means less wastewater requiring treatment and potentially receiving inadequate treatment before entering nature. This can be achieved by taking some easy steps as home such as:

  • reduce shower time
  • turn off the tap when you brush your teeth
  • wash full loads in your washing machine and dishwasher or hand wash items
  • choose eco-programmes on your washing machine and dishwasher
  • wash your clothes less frequently
  • collect rainwater for watering of your plants and garden or for washing your car
  • if your toilet has a dual flush system, use the quick flush to use 70% less water

Another way of reducing your water consumption is to fit your home with a wastewater treatment system. Such a system will treat your greywater so that it can be reused within the home and garden.

Number 2 Use Organic products

Be conscious when choosing your products. Keep an eye on the ingredients of the products you buy and keep an extra eye on the ingredients of the cleaning products, personal care, cosmetics before buying them. Buy products with organic ingredients when possible and if you do use products with ingredients that may compromise your wastewater, avoid allowing the products entering your drains. Keep in mind that products labeled “natural” are not as strictly regulated as products labeled “organic” and that these may contain potentially harmful contaminants.

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