Nitrate removal from ...

Nitrate removal from community urinals

There are some traditional and chemical methods to remove nitrates from waste generated from community urinals , here two of best methods for the process is described in details.

Using Constructed Wetlands

The removal of nitrate nitrogen (NO3-N) in natural and constructed wetland systems occurs as a result of at least three interacting processes: plant uptake, microbial assimilation/immobilization and denitrification. Most denitrifying bacteria require anoxic conditions and a labile organic carbon source to biologically reduce nitrate to nitrogen gas (N2). Plant species, such as Canary grass (Phalaris arundinacea), and common reed (Phragmites australis), produce sugar-like compounds which can subsequently be translocated to the root zone and leaked into the rhizosphere.

Figure 1 Treatment of waste water using constructed wetland

Source: http://www.armreedbeds.co.uk/

One of the most popular system for sanitation purposes might be the French Phragmifiltre® approach as this system can decompose solids that are present in the toilet waste water on top of the wetland surface and turn them in to compost. The remainder of the waste water will percolate into the gravel filter and the solluble pollutants will be decomposed there by bacteria that layer on the gravel surface. This is an aerobic stage that will mainly break down organic matter and turn the urea and ammonia into nitrate. After this stage, you will probably end up with much higher nitrate concentrations than the 20 mg/l you mention since all the ammonia will have been nitrified. So you need a second stage to remove the nitrates that have formed in the first stage. This step is called denitrification. This can be done in a second treatment wetland stage that is anaerobic. Surface flow wetlands are a simple solution here where the plant biomass will be the carbon source you need for denitrification. This system however requires quite some space. If space is not available, one can also turn towards filters with wood chips as filter material.

Using Floating Treatment Wetlands

Floating treatment wetlands differ from conventional constructed wetlands in that the microbes and macrophytes grow on and within floating platforms, and the macrophytes extend roots into the water where they take up nutrients hydroponically. In contrast, the roots of conventional wetlands grow into pond-bottom soils and are therefore not in direct contact with nutrient-rich surface-flow water. The roots from floating wetland plants also provide an additional submerged surface area to support the growth of microbes. As more roots grow, more surface area is created, thereby improving the effectiveness of the system as it matures.

Figure 2 Schematic sketch of a floating treatment wetland Source: http://the-looper.com/bioremediation.html

Nutrient-rich water can optionally be circulated through the platforms via use of submerged pumps that are powered by wind, solar or conventional electrical power. The hypothesis is that the effects of an expansive internal surface area for colonizing bacteria, in combination with improved nutrient transport to the bacteria, make relatively small floating platforms function with an efficiency equal to much larger traditional wetlands. Other benefits of floating treatment wetlands are that they accommodate fluctuating water levels; they can support either terrestrial or aquatic plants. These include some aquatic weeds, such as Salvinia, Lemna, Azolla and Eichhornia sedges like Typha latifolia and some herbaceous as well as woody plant.

Using Diatom Algae to treat nitrate in water

Diatoms are the dominant group of phytoplankton in nature and they are the best food for Zooplankton, newly hatched fish and shrimp, small fish, etc. Diatoms account for about 40% to 50% of primary production in lakes and oceans.

If you can build a small tank that gives at least 10 days retention time, i.e., tank size is 10 times the daily inflow of sewage, you can grow Diatom Algae in the tank. Diatom Algae require CO2, Nitrogen and Phosphorus for photosynthesis. Diatoms will consume the Nitrate and produce Oxygen, so there will be no foul odor. The tank can be covered with an acrylic sheet, that allows some sunlight to pass through since Diatoms require light for photosynthesis. The overflow from the tank can be released into any pond or lake nearby, the fish in the pond will consume the Diatoms. If you have space for a larger tank or pond, you can grow fish and benefit from sale of fish. You would be aware that urine is an excellent fertilizer, so it can be used to grow fish, by growing Diatom Algae.

Read more related content on The Water Network

Other sources from the internet

• Read more details about constructed wetlands HERE

• Read more details about French Phragmifiltre® approach
• Read more details about type of constructed wetlands HERE
• Read more details use of water hyacinth to treat sewage water can be found HERE
• Read more about Nualgi – Nutrition for Algae, to grow Diatom Algae in wastewater treatment plants, ponds, lagoons, lakes, etc. HERE