whereby used water – that is wastewater which can no longer be returned to the water cycle – is cleaned so that is can be used for other purposes¹. Most of the water used by homes, industries, and businesses must be treated before it is released back to the environment. Given that agriculture accounts for about 75% of total global water consumption while other industrial uses accounts for about 20%, we need special facilities to clean the water – natural processes for cleaning water would not be able to cope with such high volumes for wastewater²,³. The physical infrastructure used for wastewater treatment is called a “wastewater treatment plant”. Treatment plants reduce pollutants in wastewater to a level nature can handle.
This is very important as wastewater includes substances such as human and animal waste, food scraps, oils, soaps and other personal care products and chemicals. Wastewater also includes storm runoff which can also include harmful substances that wash off roads, parking lots, and rooftops³.
But some of these wastewater treatment plants are not suited for smaller communities both in terms of the volume and type of wastewater produced as well as the overall cost and availability of trained staff to operate them. Fortunately, there are some nature-based solutions that are also available; these can complement the work of wastewater treatment plants.
In many cases, natural wastewater treatments can be very advantageous for a variety of reasons⁴:
- Simplicity: their design and construction is very simple which means that different developers can build them while there is no need for highly qualified staff to operate them.
- Cost-effectiveness: natural wastewater treatment processes have a lower cost in terms of building, labour and maintenance; this includes low energy costs too. Having said that, they do require space and land to be effective which can be costly.
- Efficiency: they are generally rather efficient in removing most of the pollutants but this can fluctuate depending on the climate. Their efficiency is lower with low temperatures.
- Reliability: natural systems are very reliable even in extreme operating conditions as they can adsorb a wide variety of hydraulic and organic feed.
So natural wastewater treatment emerges as a viable alternative to traditional wastewater treatment plants. What is more, there are different types of natural wastewater treatment options that can be used. A couple of examples are⁵:
- One of the most popular options is constructed wetlands. These are often considered an alternative to biological treatment of wastewater from small sources of pollution. Constructed wetlands can replicate the natural processes of water purification that happen in natural wetlands.
- Another natural waste water treatment is the pond technology which as the name suggests consists of a small pond where secondary treatment of wastewater can take place. While these ponds are not suited for severely polluted wastewater, their main advantage is that they can cope they well with significantly diluted wastewater and with uneven hydraulic and organic load. What is more, these ponds are easy to design, they have a small footprint in terms of energy consumption, and have low operational costs.
Attractive as the idea of natural wastewater systems may be, it is important to bear in mind the differences in performance of those systems depending on climatic conditions as well as the need to ensure that they are fit to treat the wastewater depending on its toxicity or nature of its contaminants. In most cases, natural wastewater treatments should be combined with traditional wastewater treatment plants to ensure the best results.