Treatment of table olive washing water using trickling filters, constructed wetlands and electrooxidation

Abstract

The production of table olives is a significant economic activity in Mediterranean countries. Table olive processing generates large volumes of rinsing water that are characterized by high organic matter and phenol contents. Due to these characteristics, a combination of more than one technology is imperative to ensure efficient treatment with low operational cost. Previously, biological filters were combined with electrooxidation to treat table olive washing water. Although this combination was successful in reducing pollutant loads, its cost could be further reduced. Constructed wetlands could be an eligible treatment method for integrated table olive washing water treatment as they have proved tolerant to high organic matter and phenol loads. Two pilot-scale horizontal subsurface constructed wetlands, one planted and one unplanted, were combined with a biological filter and electrooxidation over a boron-doped diamond anode to treat table olive washing water. In the biological filter inlet, chemical oxygen demand (COD) concentrations ranged from 5500 to 15,000 mg/L, while mean COD influent concentration in the constructed wetlands was 2800 mg/L. The wetlands proved to be an efficient intermediate treatment stage, since COD removal levels for the planted unit reached 99 % (mean 70 %), while the unplanted unit presented removal rates of around 65 %. Moreover, the concentration of phenols in the effluent was typically below 100 mg/L. The integrated trickling filter-constructed wetland-electrooxidation treatment system examined here could mineralize and decolorize table olive washing water and fully remove its phenolic content.

Towards Water and Energy Self-Sufficiency: a Closed-Loop, Solar-Driven, Low-Tech Laundry Pilot Facility (LaundReCycle) for the Reuse of Laundry Wastewater

“…According to Zhang et al [45], natural ventilation trickling filters for the treatment of municipal wastewater have been receiving increased attention in recent years. Trickling filters do not require any active aeration or sophisticated equipment, and therefore have the potential to achieve high treatment efficiency while keeping operating and capital costs low [45,46]. Chang et al [47] underline that attached biofilm growth on a filter media allows for higher concentrations of active biomass than in suspended growth activated sludge systems, which allows reducing the size of the reactor.…”

Environmental Biotechnology

“…Thus, the effluent from a biological treatment system can be subjected by electrochemical technologies in order to eliminate all the toxic by-products secreting from the biological system. At this point, industrial effluents, synthetic wastewater, olive washing water, textile effluent, and vinasse, after biological pretreatment were also treated by electro-oxidation and photo-assisted electrooxidation to mineralize remnant organic compounds (Aravind et al 2016, Tatoulis et al 2017, Trellu et al 2016, Vilar et al 2018.…”

Cork Boiling Wastewater Treatment in Pilot Constructed Wetlands

“…However, CWs have been tested in effluents with a similar composition to that of CBW, mainly in wastewater containing a high organic load and phenol concentration. Such wastewater sources are olive mills [49][50][51][52], pulp and paper industry [53,54], wineries [55,56], coffee processing [57] and contaminated groundwater with refinery effluents and petrochemical industry effluent [58]. As reported in a review paper by Stefanakis and Thullner [59], various designs and wetland types have been tested with wastewater containing phenolic compounds.…”