Water scarcity is an ongoing and increasing problem. We discuss why municipal wastewater treatment is an essential solution and break down the process.
What is Municipal Wastewater Treatment and How Does it Work?
The expansion of towns due to population and industrial growth requires basic wastewater services, namely municipal wastewater treatment.
Municipalities have several wastewater treatment plants (WWTP) serving certain districts. To connect to the municipal sewer, these treatment plants require permission, and approval depends on the available hydraulic space at the respective treatment plant.
Wastewater flows to this wastewater treatment plant. Once there, it’s treated to the respective standards determined by the Department of Water Affairs (DWA) before discharging into the river.
Some plants only offer a screening of municipal wastewater and consequent discharge into the ocean. However, most plants have staff present 24/7 working shifts to monitor plant conditions because the treatment system is biological and thus sensitive to external and internal upsets.
What is Wastewater Treatment?
Wastewater treatment uses various biological conditions to allow the polluted wastewater to treat itself.
In summary, it’s creating a controlled environment where pollutants can safely break down and become less harmful to the environment.
Why Do Municipalities Treat Wastewater?
Wastewater is high in biodegradable content like organics as well as nitrogen and phosphorus. If we expose rivers or other water bodies to this type of wastewater, the following happens:
- The high biodegradable organics will break down in the water, creating oxygen-deficient conditions unhealthy to aquatic life.
- Nutrients such as ammonia and phosphorus are harmful to specific species in constant high doses. High nutrients also promote eutrophication, which is an overgrowth of algae and plant species, creating a pH drop due to carbon dioxide generation during its decaying reactions. This lower pH is undesired for aquatic life.
- Untreated wastewater flowing into rivers can have detrimental health effects on the people nearby and cause odorous air.
Therefore, companies like NuWater exist to enable municipalities to expand their treatment system, install emergency treatment systems or build a new treatment plant. By the time it has gone through the wastewater treatment, the water is ready for discharge or re-use as secondary effluent.
How is Municipal Wastewater Treated?
There are a few stages to the municipal wastewater treatment system as outlined below.
The NuWater System in a Nutshell
Stage 1: Collection
We accumulate and mix all wastewater sources into one collection system.
Stage 2: Screening
Before any treatment, the wastewater must go through various screens and grit removal. These screening steps exist to remove debris, sand, glass pieces etc., to prevent mechanical damage to our treatment equipment. After the coarse screening, we generally continue with fine screening and grit removal.
Stage 3: Biological Treatment
Next, the wastewater flows into the biological treatment. We base this type of treatment on the quality required and the feed wastewater characteristics.
It’s also the focal point of a municipal plant because it’s responsible for nutrient and organic reduction. The system produces a specific volume of sludge stream that we need to dewater, and we send the drier solids to landfills.
The dewatering process is the removal of excess water from the sludge stream for volume reduction. Dewatering can be done via a dewatering machine or gravity on a drying bed with underground drainage.
Stage 4: Solid-Liquid Separation
The Solid-Liquid separation follows the biological treatment in importance since the solids content is part of discharge effluent quality. This process is splitting the sludge generated from the biological system from the clear liquid.
After that, we discharge the clear liquid into the environment or re-use it as tertiary treatment. On the other hand, we recycle the sludge to the biological system.
We use Two Solid-liquid Separation technologies on municipal wastewater treatment plants based on the level of quality and technology the plant requires.
Each technology has its advantages and disadvantages. These technologies are:
Also known as a Secondary Settling Tank (SST). The sludge settles via gravity, where the clear liquid overflows, and we recycle the settled sludge to the biological process.
A mechanical separation where we withdraw the clear water from the sludge stream and the concentrated sludge stream recycles the process.
Stage 5: Disinfection
Before we discharge the clear liquid into the environment, it requires inactivation or removal of a certain bacteria to adhere to the discharge limit for the respective plant.
We generally use the following disinfection methods on municipal sites:
- Chlorine-based disinfection which is a Chemical Disinfection
- Ultra-Violet light (UV), which is a Non-Chemical Disinfection
Municipal Water Solutions South Africa
At NuWater, we believe in empowering municipalities with automated, scalable, efficient solutions to ensure a simple, effective wastewater treatment process.
Contact us today for all your wastewater treatment needs.