"El Toyo" wastewater treatment and regeneration plant (Almería, Spain)
WWTP El Toyo produces irrigation water from wastewater taken from the municipality of El Toyo and treats 3 000 - 4 000 m3/day from July to September and 2 000 - 2 500 m3/day on average during the rest of the year. Maximum capacity is currently 10 000 m3/day. This WWTP consists of four main stages: pretreatment, biological treatment (activated sludge process), tertiary treatment and water storage.
Treated wastewater is regenerated in the tertiary treatment by the following processes before storage and distribution:
Filtration: treated water is filtered using self-cleaning sand filters, with flow rate of 125 m3/h (sand particle diameter 0.5-1.0 mm). Filtration operation removes particulate matter/turbidity present in the treated wastewater. After filtration, water stream flows to the next stage (ozonation).
Ozonation: filtered water is treated in a two-stages oxidation process adding ozone: i) ozone production unit and ii) ozone-water mix. Ozone is produced from liquid oxygen in an ozone generator system. Then, ozone is injected in a contact tank, where organic and inorganic compounds are oxidized. Residual ozone is then chemically removed before being released back into atmosphere. Then, water is chlorinated and stored.
Chlorination: a 150 g/L sodium hypochlorite solution is injected in the main pipeline using 3 dosage pumps (44 L/h), achieving a free chlorine concentration of around 1-2 ppm.
Water storage: regenerated water is stored in a 6000 m3 concrete tank (two compartments, water depth 4.5 m).
The resulting regenerated water is characterized by an excellent composition that makes it suitable for irrigation:
- Suspended solids: < 20 mg/L.
- COD: < 5 mg/l
- BOD5: < 2 mg/l
- Free chlorine: 1 - 2 ppm
- Ozone: undetectable
Water from the service tank is distributed to El Toyo area (garden irrigation) and El Toyo Golf Course by gravity via extensive networks of water mains (main pipe: 400 mm diameter, 1.533 m length, cast iron).
The CW3000 will be tested for the disinfection step, which occurs just before the 6 000 m3 water storage tank and subsequent delivery to the municipality of El Toyo.
At the disinfection step, sodium hypochlorite is currently injected to achieve a free available chlorine concentration of the water in the storage tank of 1 – 2 mg/L. The CW3000 must ensure a free available disinfectant concentration of 1.5 mg/L to the water flow of 250 m3/h that goes to the water storage tank. Pressure in the pipe is very low, at about 0.1 - 0.2bar.
The chlorine is generally injected during the night, when the wastewater is treated. The plant operators start the water treatment at around 8 pm and after between 10 and 11 pm they leave the plant which continues to run and in the morning around 8 am they stop the water treatment. The CW3000 must operate autonomously, as no operators are present during the night. If the wastewater treatment stops for any reason during the night, the CW3000 must also stop automatically.
CW3000 set-up installed in "El Toyo" wastewater treatment and regeneration plant (Almería, Spain)