The production of juices involves the generation of wastewater, which can occur at different stages of the production process. Primarily, this includes overflow from filling machines or water resulting from various washing operations, both of the fruit and the machinery used.
For the discharge of this wastewater, it is necessary to separate toxic contaminants from non-contaminated water, so that the final water quality is suitable for discharge into public waterways, complying with the COD levels required by legislation on the matter.
Below, we detail the solution installed for a juice manufacturer (apple, pear, nectarine, and peach) that generates a wastewater flow of 50 m3/h. Production in the factory is not constant as there are two distinct production periods: from June to October, operations run 24 hours a day, resulting in a flow of water to be treated of 1200 m3/day, while from November to May, operations run for 8 hours a day, resulting in a flow of water to be treated of 400 m3/day.
1. Pretreatment Stage. The first step involves removing solid waste and particles from the washing of the fruit. After this, the effluent is pumped to a homogenization tank that will serve to store and mix the effluents from the production process of the different juices to obtain a single effluent that can be sent to the second stage of wastewater treatment. The technologies used in this first stage are:
- Fine screening (rotary filter) for the removal of solid waste and particles.
- Pumping well.
- Homogenization tank for the effluent.
2. Treatment Stage using anaerobic treatment. This is the main stage and aims to degrade the dissolved organic matter in the homogenized effluent. It is the stage where we will eliminate most of the contaminant load from the effluent and is carried out in the absence of air, resulting in biogas as a byproduct of the treatment. After this stage, it must be checked whether the obtained effluent meets the discharge limits or if it needs to undergo a third treatment phase. This stage consists of two sub-stages:
- Neutralization tank: for adjusting the pH of the effluent and for dosing flocculant and antifoaming agents.
- ECSB Reactor (External Circulation Sludge Bed), for the degradation of organic matter and the production of biogas (fuel). This biological treatment process allows operation during both high production months (24 h/day) and low production months (8 h/day).
3. Post-biological treatment stage. After the previous process, the discharge limits are not always reached, so the obtained effluent must still undergo a final biological purification process to completely remove organic matter, followed by adjustments to allow for discharge. The technologies used in this stage are:
- Aerobic biological reactor MBBR (moving bed bioreactor), for adjusting the effluent parameters to discharge limits.
- Clarification of the effluent using a flocculation + DAF flotation clarification system with lamellas.
- Treatment of sludge purge using a conical decanter and centrifuge.
After the entire treatment process, a final effluent of suitable quality for discharge into public waterways is obtained, and the only waste is biological sludge that must be sent to a waste manager. The biogas obtained in the same process can be utilized as fuel.
