We are starting a community sanitation project in schools in South Asia and want to ensure an environmental friendly, sustainable cycle for waste treatment for these community toilets.
The waste water from the sample toilet in one school that we started contains a high amount of nitrate (but natural as students use the toilets mostly to urinate). We need to treat this waste and reduce the nitrate concentration from 20 mg/L to 10 mg/L before we dispose this water back into the ground (where we are building ground water recharge trenches).
We are looking to get some inputs for designing a waste treatment system for this project. We will like to opt for simple biologically systems using bio material etc. Your inputs for selecting or designing the waste treatment systems will be very much helpful for us.
We can provide you with a Nitrate removal catalyst as well as a system to recover teh Nitrates which are good fertilizers to farming community without any niusance of smell. You can infact reuse the water after treatment for gardening and other purposes.
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
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.
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.
Thanks everyone for the suggestion. After reading the entire thread and going though some complicated solutions I feel, Mr. Mansoor has said it right - Have a wetland constructed at the site. I will be sending some real pictures of the community toilets to the water team soon. Also once we start working on treatment facility I will write about it and share picture as the water network team has suggested me.
Effective management of nitrogen in system - I was reading some research papers and happen to read this paper http://www.google.com/patents/US4210528 i feel its useful
'Suggestions required for Nitrate removal from waste water generated at community urinals'
Why don't you think of separating the urine to use as plant nutrient. It would need to dilute it and then use as plant nutrient rather going for treatment.
The urinal wastewater can be effectively treated by using free floating water plants named "water hyacinth". It has the capability to remove nitrogen present in urea nitrogen, ammonical nitrogen and nitrate nitrogen. They would prove as compared to the other treatment methods and technologies.
If you are talking for rural areas and have space, then what I understand the flow rate will not be much higher, so if you construct simple wetland growing weeds in it and let the water flow through it, and at the end of the wetland, it goes directly to your Recharging Trenches, then this will be another low cost, effective and good solution to work with.
All comments are quite correct and show the need for better information to work with. Once you have this additional information please remember it is better to reduce the waste slur into its elemental form before considering discharging it to the environment. Bacteria, fungus , and algae do not have the genetic code for organic compound reduction to elemental form. This is only found in the Archaea species of microbes. Standard US Parks and recreation highway toilet system use a 500 gallon tank, add 250 gallons of water, one 2 # container of Archaea species and to get the cat ion exchange process started they use a one quart bottle of liquid humates. The results are, 1. no odor at all from the toilets or entire rest room, 2. The feces, urine, and toilet paper are reduced to elemental form, 3. The grey or black water can be used for watering and fertilizing the local lawns or forests. Health department reports have shown NO pathogens found and the amount of dissolved oxygen is 3 times that of normal solutions. A simple water filter could be used to return the water to potable status. Very efficient for desert conditions. Old technology,yes. But still viable today.
Published
by Guy McGowen, East Coast Archaea - President
We have an Algae-Recycle System that will actually convert the urine into a functional plant food that would then be taken up by the plants and converted to CO2 or Carbon Fertilizer.
As suggested by others, the 20 mg/l nitrate you find might not be the biggest problem but in stead urea and ammonia. So I suggest you first analyze the water more thoroughly before starting to look for the best solution.
We have been treating toilet water with much success using treatment wetlands. The most interesting 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, you can also turn towards filters with wood chips as filter material.
I agree with Bruno and Morgan. I suggest you to evaluate if you have nitrate or other form of nitrogenin this effluent. Several times laboratories express results of nitrogen in a different way and it can make you to misunderstand analysis results. Please check results with laboartories chemists.
diffuse pollution is part of the whole of the organic matter rejected by the human body. the nitrate is component urine, but it also comes from part of the destruction of the fecal matter by the micro organizations. the pollution is dangerous at the moment when it is in strong concentration as in this case with the latrines and the collective cleansing. The cleansing such as it is currently practiced has big problems: concentration of multiple pollution and the transformation of the fecal matter into mud.
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. 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.
Although you may have measured some nitrate in your toilet sample, the 9.3 grams of urea in a litre of urine will eventually be broken down by bacteria into ammonia, with potential ammonia concentrations well in excess of 1000 mg/L. Bacteria in the environment will then convert the ammonia to nitrate.
Biological treatment is possible but certainly not the practical or simple biological system that you are seeking. First you need to break down the urea to ammonia. Then you would need to convert the ammonia to nitrate (nitrification). and finally you need to convert the nitrate to nitrogen gas (denitrification). Each of these stages requires a different group of bacteria and environmental conditions. For denitrification you will also need to add a readily biodegradable carbon source.
Even to use the urine as a source of nitrogen for plant growth, bacteria first need to break down the urea and convert it to nitrate.
Instead of biological treatment, you could consider using zeolite. The following link is to an article on using struvite crystallisation and adsorption to zeolite to recover nutrients from human urine collected from urine separating toilets - using MgO to precipitate struvite and zeolite to adsorb ammonia.
Hi Aiden. Interesting that you get nitrate in urine. Fresh urine typically contains nitrogen in the form of urea (organic form nitrogen). When fresh urine is exposed to non sterile environment (such as sewer systems) the urea is converted to ammonia by bacterial urease. During this transformation pH of the urine changes from approximately 6 to 9 -9.2(due to the formation of ammonia an some other weak acid -base reactions). In order for nitrate to be present in urine there has to be an aerobic period during which ammonia is converted to nitrite an then nitrate (nitrification). Even then very liittle nitrate produced as nitrite oxidisers are inhibited by ammonia, its own substrate and the high salinity of the urine. Does the urine-containing wastewater get oxygenated somewhere along the line? Could you perhaps produce a schematic diagram of the wastetwater system. If there is indeed nitrate in the wastewater, all you have to do is denitrify it. For that you will require some form of organic carbon (readily biodegradable) as energy source for the heterotrophic organisms that facilitate denitrification (if the organic carbon in the urine has been depleted).
