Water is becoming an increasingly scarce resource. As a result of water pollution caused by human-related activities, wastewater has been damaging local ecosystems across the globe. This is not only unfit for human use or consumption, but also threatens indigenous flora and fauna. In order to prevent this, wastewater treatment (WWT) is carried out to remove impurities from sewage before it reaches waterbodies or aquifers.

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There are three types of sewage: domestic, industrial and storm runoff. The first two types of wastewater can cause serious disruptions within ecosystems. Domestic sewage, also known as sanitary sewage, is wastewater from homes. While 99.9% of this comprises of water, less than 0.1% of this waste contains dissolved impurities. Despite the sewage containing a relatively small proportion of waste, it is the large quantities of domestic sewage produced and the nature of the impurities that can cause environmental problems. While most of these impurities are made of organic materials and contain plant nutrients, they also often contain disease-causing microbes.

Related: Is recycled wastewater the answer to California’s drought?

On the other hand, industrial sewage often contains chemical compounds from industry-related processes and production. It can be harmful or even toxic for living organisms to come in contact with these compounds. The third storm sewage includes substances such as organic matter and suspended or dissolved solids that contaminate the water during runoff. This can include surface runoff from nearby areas such as farms, which means that the water can be contaminated with animal waste, fertilizers and pesticides, which can then be deposited in the soil or waterbodies.

Aerial view of a sewage power plant is brown with areas of water

The effects of wastewater pollutants on aquatic ecosystems

Pollutants in wastewater include organic material, suspended solids, plant nutrients and various microorganisms.

The amount of decayable organic matter is indicated by the biochemical oxygen demand (BOD). This is the amount of oxygen required by microbes to break down organic materials in sewage. If there is more organic matter in sewage, that results in a higher BOD. Consequently, higher BODs result in less dissolved oxygen available for aquatic animals.

Suspended solids can also make up sewage. Industrial and storm wastewater typically contains higher levels of suspended solids than domestic wastewater.

Domestic sewage can also contain high levels of plant nutrients like nitrogen and phosphorus. However, if there are excess amounts of these elements in waterbodies, this can cause rapid growth of algae, which leads to algal blooms. These disrupt aquatic ecosystems as the algae produce toxins that harm animal populations and/or humans that utilize the water.

Another characteristic of domestic sewage is high levels of microbes. The majority of these are coliform bacteria produced by our intestinal tracts, among other types. This can cause disease if ingested and indicates that fecal matter is present in the water. As described above, high levels of organic matter lessen dissolved oxygen in water, impacting aquatic flora and fauna.

How WWT is carried out

There are four main methods to treat wastewater, depending on its composition. These techniques are physical, chemical, sludge and biological WWTs.

Physical WWTs

Physical processes, including straining and skimming, can be used to remove solids from wastewater. One of the most efficient methods is sedimentation, whereby heavy or insoluble particles settle at the bottom of the solution while the pure water floats above. Another technique that can be used is filtration. For this, the wastewater passes through various filters, such as sand, to separate contaminants and/or insoluble particles. This can be supplemented with skimming to efficiently remove the greasy layer that is often found floating at the top of certain types of wastewater.

To carry out these methods, one often requires heavy-duty machinery. This can negatively contribute to other forms of pollution, by virtue of the extensive energy required to power these systems.

Chemical WWTs

Chemical wastewater treatment methods involve the use of other substances such as chlorine or ozone (O3). These oxidizing agents kill bacteria and prevent them from reproducing in the water. Alongside oxidizing substances, neutralization can also be carried out to ensure that an acidic or basic solution is brought back to its natural pH of 7.

For chemical WWTs, one has to be mindful of the chemical compounds being used to treat the wastewater so as to prevent contact with harmful substances as a result of negligence.

Sludge WWTs

Sludge treatments use a solid-liquid separation process to purify water. Often a device such as a centrifuge is used to separate solids from liquids within the wastewater.

Biological WWTs

This system is biomimetic as it utilizes biological processes to decompose organic matter like human waste, oils and soap found in wastewater. This is similar to processes that microorganisms carry out in nature. There are three ways this can be done: through aerobic, anaerobic and composting processes.

For aerobic processes, microorganisms break down organic matter using oxygen and turn the material into carbon dioxide. Composting is another oxygen-utilizing process where water is treated by mixing it with sawdust or other carbon-based resources.

Conversely, in anaerobic processes, oxygen is not used. Instead, the waste is fermented at a specific temperature to decompose organic matter.

Looking to the future

Of the four main WWT processes, biological wastewater treatment solutions are a sustainable option that not only mimics natural processes, but also takes a holistic approach by optimizing the health of the planet and humankind. The EBS-Di system by EnBiorganic Technologies does this well. To ensure that this system works efficiently, non-pathogenic microbes are grown and trained to eat a specific diet of organic materials. Once they become familiar with this, they are released into the wastewater to purify the water by decomposing organic matter. For further purification, the biological sewage treatment process can be supplemented by one or more of the other three WWTs on a smaller scale.

By adopting biological wastewater treatment systems, we can ensure the safety of local ecosystems through a biomimetic approach. This also lowers costs and safety risks for those involved in the purification process.

Via Britannica, EP Online and EnBiorganic Technologies

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