Download PDF - RCBR - Rotating Cell Biofilm Reactor

RCBR – Rotating Cell Biofilm Reactor
Treatment process for wastewater coming from
biogas plants
Eco-Sistemi Srl
Piazza Manifattura, 1
38068 Rovereto (TN) Italy
Tel.+39 0464 443387; +39 348 2637051
E-mail: [email protected]
Web: www.eco-sistemi.org
P.IVA:08108570964
Treatment process of ECO-SYSTEMI for wastewater coming from biogas plants
Wastewaters from bio-mass plants after the solid-liquid separation, are strongly rich of nitrogen and poor of carbon
made organic compounds. From the biological treatment point of view, they could be defined as an "unbalanced"
wastewaters considering the nutrient.
We can synthetically recap the (simplified) biological reaction about carbon and nitrogen in the depurative process:
Carbon removal
C6H12O6 + 6O2 -> 6CO2 + 6H2O
This first reaction describes the organic carbon mater oxidation and it has also been named cellular respiration,
because it happens an oxygen consumption; the oxygen joins the degradation of a complex molecule (here it is
represented by the glucose, C6H12O6), with the aim of the production of the necessary energy for the cell's life.
Nitrogen removal
Nitrogen is the most important element for the bacteria, because it is contained into the amino acids and then into
the protein. Its biological interest is also determined from the various forms in which it is used and transformed by
the living organisms.
In the wastewaters, nitrogen is mainly presented under ammonia form, NH3, or NH4+ (ammonium).
If highly concentrated, the ammonia is a dangerous compound for the ecosystem: particularly for the groundwater
and for the surface water: it is necessary to foresee, in the purification process, its removal from the waters before
they get into the environment. The final compound in which it is transformed is the molecular nitrogen, N2, which
releases into the atmosphere like an inactive gas. From ammonia, the molecular nitrogen formation involves
different bacterial species and biological reactions; see the following simplification:
Ammonia nitrification (phase 1)
NH4+ + ½O2 -> 2H+ + H2O + NO2This first step is at the expense of a bacterial genus called Nitrosomonas.
Ammonia nitrification (phase 2)
NO2- + ½O2 -> NO3The second step takes place thanks to the action of bacteria belonging to the Nitrobacter genus.
© 2014 Eco-Sistemi S.r.l • Piazza Manifattura 1 - 38068 Rovereto (Italy) • P.IVA:08108570964
Tel.+39 0464 443387; +39 348 2637051 • www.eco-sistemi.org
Nitrates produced in this way aren't toxic like ammonia, but they can further be reduced to a compound absolutely
inactive like molecular nitrogen, through a biological denitrification process that takes place without oxygen, at the
expense of heterotrophic bacteria flora (it feeds of organic substrate to live, releasing carbon dioxide as a reaction
product, at the same manner of cellular respiration). This is the synthetic reaction:
Nitrates reduction or denitrification
5CH3OH + 6NO3- -> 3N2 + 5CO2 + 7H2O + 6OHIn the denitrification process, together with the nitrates reduction, at the same time we have the oxidation of many
organic compounds in the wastewaters, and also the consumption of pollutants dissolved in the same wastewaters.
As represented in the reaction indicated above, the nitrification happens with a carbon source essential contribution
(here it is indicated by methanol molecule, CH3OH).
The problem of biomass plants, as written above, is represented by the lack of biodegradable compounds of
available carbon in the wastewaters to be treated, in relation to the amount of nitrogen under ammonia or nitrates
form, depending on the typology of wastewaters to be treated.
In fact, the lack of carbon ensures that the process of nitrogen removal stops at its nitrate oxidation; it makes
inadvisable the application of the traditional biological process for the nitrogen removal with this kind of
wastewaters, unless to resort to wastewaters expensive enrichments with organic additives (for example, methanol)
which provide for the lack of carbon borrowing from an external source.
ECO-SISTEMI technological solution is a natural solution, in full compliance with the process sustainability. In
the treatment process an algae reactor is enforced, fed with treated output waters, rich of nitrates which support
their development. Algae, encouraged by the fertilized environment and by the habitat culturing they are cultivated
in, grow in a fast way fixing the necessary carbon for their structure directly from the atmosphere – photosynthesis
is the contrary of cellular respiration reaction – making bio-mass rich in carbon, necessary for wastewaters
nitrification:
Photosynthesis
6CO2 + 6H2O -> C6H12O6 + 6O2
As a WWTP, adaptable RCBR modules are used: they can be set up both in anoxic mode for the denitrifying phase,
both in aerobic mode, for carbon oxidation phase and nitrogen nitrification: this makes the plant theoretically
expandable to infinite, thanks to the plug&play connections the same devices are made of. A settling phase
specifically designed by ECO-SISTEMI subsequent the RCBR biological reactor, works for the separation of process
muds which are recirculated at the beginning of the reaction division or they are reintroduced before the bio-mass
anaerobic digester, as overflow mud.
The process can be equipped with sensors, mechanized with specific probes and equipped with
remote control for consumption and trend of the whole plant control.
© 2014 Eco-Sistemi S.r.l • Piazza Manifattura 1 - 38068 Rovereto (Italy) • P.IVA:08108570964
Tel.+39 0464 443387; +39 348 2637051 • www.eco-sistemi.org
Scheme of the treatment process of ECO-SYSTEMI for wastewater coming
from biogas plants
© 2014 Eco-Sistemi S.r.l • Piazza Manifattura 1 - 38068 Rovereto (Italy) • P.IVA:08108570964
Tel.+39 0464 443387; +39 348 2637051 • www.eco-sistemi.org