Unravelling the Facts: The Story Behind Wastewater Management in Tywyn and Dolgellau
Sewage transported from Dolgellau to Tywyn
Written by CEO Laura Owen Sanderson
In recent news surrounding wastewater management in Tywyn and Dolgellau, various claims have emerged. North Wales Rivers Trust decided to investigate, we present a concise summary of the facts, including statements from Dwr Cymru and our observations on the treatment plants' comparisons and our verdict at the end.
Frontcover of the Cambrian News 25/5/2023
Dwr Cymru, responsible for wastewater treatment, has confirmed ongoing work at the Dolgellau wastewater treatment works due to work on a treatment tank. This means that Dolgellau wastewater treatment plant has reduced capacity to treat effluent on site and it must be treated elsewhere.
Due to limited capacity at the Dolgellau site, tankers are being utilised to transport four tankers of wastewater per day to the larger Tywyn treatment works for cleaning and treatment. Dwr Cymru asserts that this is a routine procedure to ensure adherence to environmental standards.
Dwr Cymru statement:
“We are currently carrying out work at our Dolgellau wastewater treatment works. While this work is being done, we have less room to treat water on site in Dolgellau. This means that we are using tankers to carry some of the wastewater from Dolgellau to our larger nearby Tywyn treatment works where there is plenty of room to clean and treat the water before it is safely returned to the environment.
This means that you may notice more tankers in the Tywyn area for the next few months coming and going from our wastewater treatment works, but please be assured that this is routine procedure to treat wastewater from other sites in a larger treatment works while maintenance or upgrades are being carried out on our sites.It simply means that we are treating a little more wastewater at our Tywyn treatment works than usual before it is safely returned to the environment.
We are aware of claims locally that the tankered waste is being put straight into the sea but we can confirm this is most definitely not the case.
Following reports in the media and on social media over the weekend regarding water quality in the Tywyn area, Natural Resources Wales have confirmed that this is a natural occurrence and not linked to any of our assets.”
We can confirm that Dwr Cymru have stated that no RAW sewage (untreated) is entering the sea in or around Tywyn from the treatment works or the tankers. All sewage is being treated using the process outlined above. However, once treated the effluent is being discharged via a sea outfall at Tywyn.
North Wales Rivers Trust asked Dwr Cymru to provide the differences in wastewater treatment plants for comparison and the results are below:-
Tywyn:-
Total PE (population equivalent): 6,456
Process Summary
· Storm Treatment
· Preliminary Treatment (Grit Plant, Screening Facilities)
· Primary Settlement
· Biological Treatment (Biofilters)
· Secondary Settlement
· Sludge Treatment (Sludge Storage, Thickening/Dewatering)
· Tertiary Treatment (UV Plant)
After treatment, final effluent is discharged via a sea outfall at Tywyn.
Dolgellau:-
Total PE (population equivalent): 4,662
Process Summary
Storm Treatment
Preliminary Treatment (Grit Plant, Screening Facilities)
Biological Treatment (Aeration)
Secondary Settlement
Sludge Treatment (Sludge Storage, Thickening/Dewatering, Centrifuge)
After treatment we have not confirmed where the final effluent is discharged. *Although this plant is currently not working at full capacity due to a damaged tank.
It is crucial to examine the comparisons between the two treatment plants. The Tywyn treatment works has a higher population equivalent (PE) of 6,456, while Dolgellau has a PE of 4,662. Both facilities employ preliminary treatment processes, such as grit plant and screening facilities, to remove larger debris. However, Tywyn utilises biofilters for biological treatment, whereas Dolgellau employs aeration.
Biofilters excel in removing organic matter and controlling odors, while aeration systems, such as activated sludge, are highly effective in removing organic matter, suspended solids, and pathogens.
Additionally, Dolgellau incorporates centrifuge technology in its sludge treatment stage.The choice between centrifuge treatment and UV (Ultraviolet) treatment for sewage depends on the specific goals and requirements of the wastewater treatment process. Tywyn does not have a centrifuge system and this could potenitially result in longer processing time.
Centrifuges are known for their rapid processing capabilities. In comparison, sludge treatment processes without centrifuges may require longer processing times to achieve desired dewatering or thickening results. This can impact the overall efficiency and throughput of the treatment system. Both technologies have distinct functions and applications:
Centrifuge Treatment: Centrifuge treatment is primarily used for sludge dewatering and thickening in the later stages of sewage treatment. It focuses on separating the solid components from the liquid fraction of the sludge, reducing its volume and moisture content. Centrifuges are effective in achieving high solids capture and producing drier sludge for easier handling and disposal. This technology is crucial for sludge management and can significantly reduce the volume of sludge that needs further treatment or disposal. ( Dolgellau)
UV Treatment: UV treatment, on the other hand, is a disinfection method that targets microorganisms present in the wastewater. It involves exposing the water to UV light, which damages the DNA of bacteria, viruses, and other pathogens, rendering them inactive or unable to reproduce. UV treatment is commonly applied as a final step in the sewage treatment process to ensure the removal of harmful microorganisms before the treated water is discharged into the environment or reused. UV treatment does not remove or separate solids from the wastewater; its primary function is disinfection although other processes happens at Tywyn prior to this treatment. (Tywyn).
*It is important to clarify that specific details regarding nutrient removal capabilities and the effectiveness of treatment processes have not yet been requested but we will update the article when we have this information.
Stock Image- Algal Blooms
Recent reports from water users have noted that algal blooms have started to appear in the sea at Tywyn. Natural Resource Wales have investigated and stated that these blooms are a natural occurrence and not linked to any Dwr Cymru assets or outfalls. We are requesting further clarification from NRW as to what these blooms are and if they are natural or from diffuse or point source pollution.
Background- Algal blooms near sea outfalls can have various causes, and it is important to consider multiple factors when assessing their origin. While natural causes, such as increased sunlight, warm weather, and nutrient availability, can contribute to algal blooms, it is also possible for sewage discharge to be a contributing factor. Sewage contains nutrients, including nitrogen and phosphorus, which can act as fertilisers for algae growth.
To determine the specific cause of an algal bloom near a sea outfall, a thorough investigation is necessary. This typically involves analysing water samples, assessing nutrient levels, and identifying the type of algae present. The presence of sewage-related indicators, such as elevated nutrient concentrations or fecal indicator bacteria, can provide evidence of sewage contribution.
Additionally, monitoring the timing and location of the algal bloom can help determine if it coincides with periods of increased sewage discharge or other potential sources of pollution. Algal blooms that persist or intensify in the vicinity of sea outfalls may indicate a higher likelihood of sewage influence.
It's worth noting that the occurrence of algal blooms can be complex, influenced by a combination of natural factors and human activities. Sewage treatment plants employ various processes to minimise the release of nutrients and potential pollutants, including the use of advanced UV treatment technologies and adherence to regulatory requirements. However, occasional discharges or failures in the treatment process can still occur, potentially contributing to algal blooms.
The prolonged hot weather has attributed to more intensive algal blooms across the country. The sources can be varied from agriculture, septic tanks and sewage treatment plants or natural occurences- Seaweed (macroalgae) and phytoplankton (microscopic algae) are a natural part of the marine and freshwater environment. According to the NRW bathing status report neither seaweed (macroalgae) or Phytoplankton (microscopic algae) have appeared on this beach. Phytoplankton which naturally increase in number at certain times of the year can occur at any beach during the bathing season and are usually noticeable by a surface scum. This beach has no history of such blooms. However, NRW have ruled out any blooms are coming from sewage at the Tywyn plant.
In the latest Cambrian News former town councillor for Tywyn and current Chairman of Tywyn and District Chamber of Tourism and Commerce (CTC) Mike Stevens says,
“Our beach is our biggest asset and the reason thousands of people come to Tywyn, it is vital to the economy of the town.
“Any pollution of our beach and coastal waters is not acceptable but to have raw sewage from another town dumped on us is totally unacceptable. ”
Tywyn bathing water status
Tywyn has been awarded designated bathing status. This means that regular water quality monitoring takes place. Tywyn bathing water is located within the Lleyn Peninsula and the Sarnau Special Area of Conservation, with the Dyfi Site of Special Scientific Interest just to the south, confirming the high conservation status of the area. The water quality sample point is located a kilometre west of the car park.
Bathing water status - 2021- Present day
The recent bathing water status has been excellent ( 2022). However in the month of August there is historically a spike of escherichiaColi. This is when a peak number of visitors descend on the area increasing the output of effluent. We will therefore be asking Dwr Cymru to reduce transport during this period.
Dwr Cymru have confirmed that the situation is likely to continue to October 2023. We are unclear how long this system has been in place but the Cambrian news report 6 months to date. We asked Dwr Cymru to provide details on spill volume to date and if they are within their regulatory permits for this site. We did not recieve volume data but Dwr Cymru confirmed that they are permitted on pass forward flow which they are currently fully compliant with.
“Our contractors are currently working on repairing the tank and this work should be finished by October but we are doing everything we can to finish sooner than that if possible. In the meantime we are also carrying out other work on site which should reduce the need to tanker flows from the site over the next few months. ”
Verdict
The situation is not ideal. In the short term it would appear that Dwr Cymru have no other option but to transport effluent to their nearest sewage works with extra capacity.
Moving forward we are seeking clarification on the following:-
As Tywyn is a holiday destination with peak pollution incidents during August we will be asking Dwr Cymru if they have taken the extra capacity into consideration and diverting elsewhere during this period.
We will request clarification from Dwr Cymru regarding the daily volume carried by each tanker and the remaining capacity during periods of high footfall, such as tourism influx.
Due to Tywyn having no Centrifuge system we will be asking Dwr Cymru for further detail regarding specific details of nutrient removal capabilities and the effectiveness of treatment processes, volume and processing time and to confirm that 100 percent of effluent is treated.
We will also be asking for clarification on extreme weather evens such as this weekend ( storm predicted) and the extra surface run off affecting the chances of raw sewage spillling directly into the sea. Will there be a reduction/ stop to effluent being transported during and after ( 48 hours) of a storm/ rain event.
We will be asking NRW for further clarification on the algal bloom tests and results and the likely source for these blooms.
Dwr Cymru have confirmed they are working hard to rectify the situation as soon as possible and that no extra raw sewage will be entering the sea due to the extra effluent. We will continue to investigate and ensure that no ecological damage results from the extra effluent and that management is in place during periods of high capacity (August) and storms/ rainfall.