Biological nitrogen and phosphorous removal project (Mining exploitation in the Zamora-Chinchipe region, Ecuador).

03 - September - 2021

In September 2021 a new and exciting project was delivered for a mining company located in the south of Ecuador. The challenge involved the design and construction of a biological wastewater treatment plant in just 6 weeks.

The mining camp had an existing WWTP that treats wastewater from bathrooms and kitchens. However, the water from the secondary settling of this WWTP contained high levels of nutrients.

The discharge of nutrients, especially nitrogen and phosphorus, causes eutrophication in surface waters. Seasonal algal blooms are a common example of this eutrophication. It causes serious problems for ecosystems and people due to low dissolved oxygen, fish kills, turbid water and depletion of flora and fauna.

To avoid this problem, BIOBOX® proposed a compact solution in a container after the existing pre-treatment. This offers a technically and economically feasible solution with a very small footprint (1 x 40′ container).

The plant is designed to remove COD, nitrogenous pollutants (ammonium), nitrates and phosphorus from an influent of 150 m3/day.

The plant’s water treatment line is organized in three stages: an initial pre-filtration, a biological denitrification and a biological nitrification.

Initial pre-filtration is performed with Filtralite® Pure NC 1.5-2.5, to laminate SS peaks. This is followed by intense anoxic denitrification in three pressurized filters filled with Filtralite® Clean HC 2.5-5. Denitrification, with addition of organic matter, in addition to the remaining BOD in the wastewater, is fully automated. It uses probes for NO3, ORP, pH, flow rate and is controlled by a PLC. This approach is very similar to the nitrate abatement plants that BIOBOX® produces for the treatment of well water in drinking water with high concentration levels of this NO3. Finally, the water is treated in a nitrifying biofilter on a bed of Filtralite® HC 2.5-5, with the addition of alkalinity, for the removal of ammonia nitrogen.

The plant was originally designed to treat 250 mg/l of nitrates (NO3) and 60 mg/l of ammonium (NH4+), in compliance with the 10 mg/l output. However, in the end, 400 mg/l nitrate (NO3-) and 60 mg/l ammonium (NH4+) were treated with the same output compliance. Also, this process consumes more than 6 mg/l of phosphorus to comply with the IFC standard.

Like all installations of this type manufactured by BIOBOX®, the entire treatment line is sensorized. It works automatically and sends all analytical and performance data to a central server.

The installation met some milestones in terms of planning and execution, from project definition to delivery to port in less than 5 weeks.

Commissioning consists of a “plug&play” and start-up of the biological systems on site. In addition to remote monitoring, there is a complete transfer of operational and maintenance knowledge to the end user during the start-up phase.

In conclusion, this plant proved to be the best solution for a total nitrogen elimination of 90%, complying with river discharge regulations and allowing the mining company to successfully continue with its policy of minimizing environmental impact.

Technologies used:

Plant characteristics:

  • Flow treated: 150 m3/día
  • Inlet nitrate concentration: 400 mg/l
  • Inlet ammonium concentration: 60 mg/l
  • Total Nitrogen output: <10 mg/l complying in accordance with IFC regulations for discharge into watercourses.
  • Inlet COD concentration: ≈ 500 mg/l
  • Outlet COD concentration: < 15 mg/l
  • Phosphorus inlet concentration: 8 mg/l
  • Phosphorus concentration output:  2 mg/l
  • Filter material: Filtralite®

Plant steps:

The water treatment line consists of three steps:

Initial pre-filtration
Biological Denitrification
Biological Nitrification