The electrocoagulation unit is able to treat up to 10 m3/h. The waste water flows through several in-line electrodes. Cathodes are made of stainless steel and the anodes made of recycled aluminium are oxidised and play a role as coagulant, precipitating nutrients and solids.
Phosphorous and Nitrogen removal at laboratory scale
Several tests with different current densities show a range of nutrients removal.
At laboratory scale 100 % and 70 % of P and N removal ( respectively) is reached but it implies higher energy consumption.
Phosphorous removal at pilot scale
The phosphorus concentration in the influent (blue line) fluctuates depending on the operations running in the production centre. In a continuous mode, the electrocoagulation unit removes between 30 -55 % of the initial phosphorus. The removal rate oscillates due to the presence of other components in the waste water which can compete with the aluminium oxide available as coagulant.
Other parameters at pilot scale: Temperature
The increase of temperature is an advantage in the process. The coagulation process is followed by a biological treatment where one requirement is a temperature higher than 30 º due to losses from one point of primary treatment in the WWTP to the anaerobic digester (secondary treatment) and the temperature is reached thanks to several deposits working as heaters.
Other parameters at pilot scale: pH
Biological treatment requires neutral pH which is fixed using HCl or NaOH previously. This parameter has been measured before and after electrocoagulation process. As it is shown in the figure, pH is constant, as well acid as basic. Only highlight a slight tendency to neutrality with acid pH in continuous mode.
FLUIDISED BIOELECTROCHEMICAL BED REACTOR
The FBBR is based on the interaction between electroactive microorganism and a fluidised electrode which works as anode. The organic matter is oxidised by the bacteria and the electrons are transferred to anode and therefore to the cathode.
COD removal and biogas production
The pilot FBBR operating in continuous mode is able to remove more than 90% of organic matter (COD) and produces biogas with high content in methane and hydrogen in steady state.
Cathode configuration modified at pre-pilot scale
Optimizing the electrode material and configuration improve the amount of current that flows between electrodes which is co-related to the COD removal rate. In this case, using cathodes made of stainless steel and a sponge shape, increase the available surface and enhance 22% of current.
Parameters at pre-pilot scale vs. anaerobic digesters
Thanks to the ultrafiltration pilot plant, turbidity decreases under values allowed by the Spanish Law, accomplishing the R.D. 1620/2007 for water reuse.