Diatom Algae grow even beneath ice -
Arctic - www.windows2universe.org/earth/polar/arctic_marine_life.html
Antarctic - blogs.jcvi.org/tag/diatom/
Lake Erie - www.sciencedirect.com/science/article/pii/S0380133011002619

Diatoms are 'plants' not animals. They only consume the nutrients in the sewage.

Our process is so simple that you do not have to harvest the Diatoms, you can allow them to die and sediment.

Or you allow them to flow out with the treated sewage, the Diatoms would be consumed by the fish in the receiving waters. This is better than allowing nutrients to flow out, this only causes unwanted algae such as Cyanobacteria to bloom.

Farmers use manure to grow crops.
ec.europa.eu/programmes/horizon2020/en/n...king-most-pig-manure
"Traditionally, farmers disposed of this mix of urine, faeces and waste water by simply spreading it on the ground as fertiliser."

So what is the problem in growing algae in sewage and allowing fish to feed on the algae?

I would imagine that this would be more suitable in a climate with higher temperatures and sunlight. This is scarce in northern Europe.

How are the diatoms harvested and used?

In Europe you cant feed animals to animals that have been fed on human waste(sewage).

Regards
Seamus.

Any open tank will do to grow Diatoms. They require light for photosynthesis.

The tanks need not be of any particular type, a natural pond, a plastic sheet lined lagoon, etc., will do.

Retention time is important, Diatoms require a few days to consume the ammonia / other forms of N and phosphate, so if the tank is big enough to give retention time of more than 7 days, complete removal of nutrients is possible.

Diatoms can be grown even in the public waterways into which the treated sewage is being released into. This may not help you meet your license obligations of discharge limit at your discharge point, but will help keep the receiving water clean.

Bhaskar,

For Ammonia in treatment plants do you have a suggestion on how a reactor or tank could be set up to test this.
What conditions are needed to promote diatoms?

Regards
Seamus.

Growing Diatom Algae is a good way to deal with ammonia.

Diatoms consume ammonia and produce oxygen and the diatoms are consumed by zooplankton and fish, so they do not accumulate in the water unlike other algae.

Typically, energy costs are more in developed countries. My experience in developing country shows that aerobic systems can be cost-effective.

F H Mughal

Dear Mr Kelly

Aerobic stabilization of organic pollution (TSS,COD,BOD) requires substantial amount of energy for aeration, agitation and pumping. Anaerobic treatment in "High Rate Anaerobic Reactors" like e.g. ABR can do this job with much lower energy requirement. But when it comes to Ammonia removal aerobic treatment is required since nitrification requires oxigen.
Hence it may be a valuable option to make anaerobic treamtment first and for ammonia reduction you may introduce an aerobic step afterwards.

Best Regards

N.Zimmermann

Just to clarify. The size of plants is 10 p.e. to 80,000 p.e.

I work in the wastewater industry in Ireland and have operated WWTP and AD Plant from 10 to 80,000 p.e in size.

Our systems are very energy hungry and I would like to promote low energy treatment systems.

ABR looks like a good option but for larger scale operations you would need a low energy way of removing ammonia. In Ireland a lot of effluent from treatment plants is discharged to water courses. For discharges to water courses, ammonia is often the limiting nutrient in discharge licences.



Can effluent from ABR to the start of the process. Would this help to remove ammonia or would this inhibit the process.


Kind Regards
Seamus Kelly

Dear Frapoberlin and Marijn Zandee

My inputs to your initial question:

1. Under anaerobic conditions the Nitrogen gets maily hydrolised into NH4 which is a equilibrium with NH3 depending on pH. Just a percentage (depending on the anarobic system) of the Nitrogen gets removed from the wastewater by uptake of active bacteria (for their growth) and by sedimentation processes (sedimentation into primary sludge).
Therefore you will have even higher NH4 level in the effluent than in the raw wastewater.
A level of 150mg/L NH4 in the effluent is quite high and tells me that the raw wastewater has high Nitrogen content (maybe source seperated black water).

2. The anaerobically treated waster should be reused for irrigation purposes. Than the nitrogen content is an advantage, because its a fertilizer. If you apply this treated water on a sound soil, plants can uptake the nutrient and the nitrogen undergoes nitrification-denitrification process. The soil is a very effective treatment step (see Soil Aquifer Treatment SAT).

3. To use of an Anaerobic Filter (AF) after a Anaerobic Baffled Reactor (ABR) may make sense, since anaerobic filters (attached growth) have a very good treatment performance in terms of COD,BOD and TSS, but the AF prones to clogg if no ABR is put in advance. As per my field experiences the setup Settler-ABR-AF gives best treatment performance and stability and you can reach COD,BOD and TSS reductions of more than 90% (depending on the design).

4. If you like to reduce the nitrogen you may have to introduce an aerobic treatment step. But see, we use a hell of energy to fix the nitrogen out of the air and produce artificial fertilizer. Than we use this fertilizer to produce food, we eat the food and excrete the nitrogen and produce wastewater, and then we use again energy and resources to reduce nitrogen back in N2, thats not an advantageous concept.

Write me if you need anything regarding High Rate Anaerobic Reactor technology like ABR and AF.

Best Regards

Nanchoz

Hi Frank,
I agree with most percpectives.
Just one point. I would not install aerated lagoons. I would alwasy go for SBR lagoons. Aerated lagoons have very, very limited nitrification capacity.
A SBR lagoon offers basically the same investment costs as an aerated lagoon, but much higher results and very much more flexibility to react on operational situations. The stability is almost the same. Sludge build up as well (when yoou let go the SBR excess sludge to the lagoon. something like this.
Sorry I forgot how to load a picture and did not fid the description for it.
Christoph

Dear Christop,
thanks a lot for your many remarks and food for thought.
I would like to add some aspects, and also refer to your ideas:

1. In our waste water programme in Vietnam, we never use the term DEWATS. We believe this is too much narrowing down the idea of decentralised WWT. What is wrong with a lifting pump? In 90% off all cases you will need them, especially in flat and flood prone areas like Vietnam. What is wrong with an aerator where sufficient space for a naturally aerated lagoon is not available? It all depends on the framework conditions, see also point 3 below. Even "pure" DEWATS plants with no electricity consumption at all will fail if nobody cares.

2. Nevertheles,, we believe that ABRs and AFs as promoted by DEWATS fans are very useful components of a decentralised system. Your doubts on the combination of ABR and AF is an interesting issue. We may go for a combination of both in one chamber, since we have learned that O&M teams often remove all (!) sludge, so no bacterias are left for doing the cleaning job. Fixed bacterias might reduce this problem.

3. In our programme, we keep repeating again and again: it is not about technologies, it is about framework conditions! Let's first have the preconditions in place , before investing into technologies that cannot be operated due to unsustainable framework conditions. We need a sound sector financing (polluter-pays-principle, cost recovery, etc.), we need local waste water regulations, we need lots of IEC to be done to raise peoples' understanding of the many threats created by waste water. We need community involvement. And last but not least we need skilled and experienced operators, especially for the many decentralised plants (decentralised treatment - centralised O&M). All this is a long way to go.

4. We use our demonstration plants for capacity building and training purposes, in order to achieve the aforementione targets. Under the prevailing conditions in Vietnam, the plants CANNOT work properly. By involving decision makers, operators, communities etc., we re trying to make them understand about the many hurdles and bottlenecks that need to be solved in order to get the decentralised approach up and running.

5. I forget to mention about our treatment plant's components:
pumping station -> ABR + AF (made from bamboo, very cheap) -> aerated lagoon. There was no space for a constructed wetland.

Thanks again, and best regards
Frank