Treatment of table olive processing wastewater (TOPW)

Transcription

1 Treatment of table olive processing wastewater (TOPW) Διαχείριση υγρών αποβλήτων από την επεξεργασία βρώσιμης ελιάς Dr. Georgios Pilidis, Emeritus Professor Department of Biological Applications & Technology University of Ioannina

2 Table Olive World Production Trent is increasing: tons/year ( ) Production Consumption Spain Egypt Turkey Algeria Greece Morocco Italy In Egypt/Turkey/Algeria and Morocco, consumption increased dramatically over the past 25 y. Italy is the only Med country where the consumption exceeds the production.

3 Treatment procedure for green and black olives Green Olives (Spanish type) Crop selection Crop cleaning De-bittering (NaOH)* Washing Canning Operation September to November Wastewater m3/ton olives *during this step, oleuropein, the most valuable compound in table olives is breaking down to hydroxytyrosol, elenolic acid and β-d-glycopyranose Black Olives Crop selection Crop cleaning Fermentation (NaCl) Canning Operation Over the year Wastewater m3/ton olives

4 Problem definition 1993: New build Greek table olive producing company (capacity: 5000 to tons green olives, costs: 3 million ) located in the industrial zone of Lamia (central Greece): lack on wastewater (ww) management system-out of operation for many years. 1998: Research project funded by GSRD ( ) with the aim to develop of a new technology and to build a large pilot plant covering 30% of the total wastewaters. Partners: Harokopion University (Prof. C. Balis), University of Ioannina (Prof. G. Pilidis) 2001: Pilot plant for 100 m3 ww/day in operation

5 Characteristics of wastewaters for acceptance by the industrial zone authority (ETVA) Parameter BOD COD Suspended solids Phenols Detergents Chromium (VI) Heavy metals ETVA Limits in ppm (concentration of relevant parameters in waste waters fresh-older) 500 ( ) 1200 ( ) 500 ( ) 5 ( )

6 Sample pre-treatment for separation of organic compounds in TOWW Wastewater Sample centrifugation and acidification to ph 2; addition of 10 ml conc. NaCl; Extraction with t- butyl methyl ether Water Fraction-1 1N NaOH; extraction with t-butylmethylether Organic Fraction-3: Basic compounds Water Fraction-4: Adjustment to ph 7-8; Extraction with t-butyl methyl ether Water Fraction-8 Analysis of sugars and amino acids Organic Fraction-9: Derivatization and analysis of phenolic bases after derivatization with BSTFA BSTFA: N,O-Bis (trimethylsilyl) trifluoro acetamide Organic Phase Fraction 2 Filtration through celite 545; Extraction with NaHCO 3 Water Phase Fraction 5: Acidification with 2N sulfuric acid till ph 2; Extraction with t-butylmethylether Addition of Na 2 SO 4 and filtration-analysis of phenolic and organic acids after Derivatization with BSTFA Organic Phase Fraction 6: Extraction with 1N NaOH Water Fraction 7: Acidification with 2N sulfuric acid; extraction with t-butyl methyl ether; drying and filtration; Derivatization with BSTFA; Analysis of phenols with GC/MS

7 Concept 1. Acidification with conc. sulfuric acid to ph Aerobic biological treatment using Aspergillus Niger fungi 3. Sedimentation 4. Advanced oxidation procedure Fenton s reagent or electrochemically 5. Sedimentation with calcium hydroxide to ph Neutralization

8 Inoculum

9 Biological treatment Laboratory experiments Experiments in the lab: bubble column, upflow 12 L vol. Pyrex glass bioreactor; was supplied air at a flow rate of 12 L/min from the bottom to guarantee aerobic conditions of at least 3 mg/l dissolved oxygen. The successful operation of the biological treatment foresees: acidification (H2SO4) till ph 4-5; installation of micellar species Aspergillus niger, very mild aerobic (light bubbles from the bottom) conditions otherwise the microorganisms can be destroyed. The hydraulic time in a continues flowing system is approx. 48 hours.

10 Influence of inoculum concentration Inoculum concentration and COD removal (in ppm) Raw wastew ater 10 4 Spores/ ml 10 6 Spores/m l 10 8 Spores/ ml COD Inoculum concentration and phenol removal (based on the sum of single phenols, in ppm) Raw wastew ater Raw wastewater 10 4 Spores/ml 10 6 Spores/ml 10 8 Spores/ml 10 4 Spores/ ml 10 6 Spores/ ml Phenols Spores/ ml

11 Chemical oxidation-fenton s reaction Among different types of mechanisms in the wastewater business, the Fe(II) regeneration mechanism has been established: Fe 2+ + H 2 O 2 Fe 3+ + OH + OH _ Fe 2+ + OH Fe 3+ + OH _ OH + H 2 O 2 HOO + H 2 O Fe 2+ + HOO Fe 3+ + HOO _ HOO + Fe 3+ Fe 2+ + O 2 + H + Weiss and Willstäter believed that also the OH were regenerated according to: OH + H2O 2 O-O _ + H + + H 2 O O-O _ + H + + H 2 O 2 OH + O 2 + H 2 O

12 Chemical oxidation Laboratory experiments Using Fenton s reagent Experiments where performed by different: Ferrous sulfate concentrations: 0.2 g/l; 0.5 g/l; 0.8 g/l. Ferrous sulfate types: FeSO 4 x 7 H 2 O; FeSO 4 x 4 H 2 O, FeSO4 x H2O (free-flowing p.s. < 20 μm) Hydrogen peroxide concentrations: 2 g/l; 4 g/l; 6 g/l and 8 g/l. Hydraulic time: 1 h and 2 h. Using electrochemical oxidation Electrolysis vessel: 500 ml glass beaker with electrodes connected to a 12 V power supply (batch mode). Three types of electrodes tested: Iron cylinders 170 mm x 7 mm Stainless steel plates 140 mm x 17 mm x 2 mm Titanium alloy mesh plates 150 mmx 40 mm x 1 mm Current intensity and energy consumption were continuously monitored. H 2 O 2 concentration has been tested for: 0.0; 2.5% and 5%. Time: 30 min, 60 min

13 Chemical Oxidation - Results Fenton s reagent COD and Phenol removal (ppm) After biology After oxidation COD Phenols After sedimen tation Electrochemical oxidation COD and Phenol removal (ppm) After biology After oxidation COD Phenols After sedimen tation

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18 Conclusions Ι TOPW can be pretreated in order to be accepted by central biological treatment plants. If the chemical oxidation step can be designed to be more efficient, the methodology can be also used for factories outside of industrial areas. The operational costs of the unit were calculated in context of: chemical and electricity costs, personnel costs, chemical an microbial analysis, as well as costs for the sludge transport (after drying) to the sanitary landfill, increase the price of table olives by 0,02 /kg. Amortization of investment costs were not taken into consideration by this calculation.

19 Anaerobic co-digestion of agricultural waste-wastewaters Management of agricultural wastes in south-east Mediterranean Scarcity of large industrial facilities Many small units dispersed in the region Seasonal character of some wastes Lack of critical mass of feedstock for an economically viable treatment system Co-digestion in a bio-refinery is the best solution for a sustainable management system Compatibility between the different waste-wastewater types should be investigated In our Lab: pig & cattle manure, poultry wastes, TOPW, OMW, slaughterhouse wastewaters, food wastes, fur farming wastes.

20 Anaerobic co-digestion of TOPW, cattle and pig manure First results (J. Agr. Eng. Res. 2001): AD was able to remove only 12% of polyphenols and 49% of other organics in TOPW Co-digestion: resolves problem of toxic and inhibitory compounds accumulation Provides additional advantages by synergetic phenomena between the microorganism providing nutrient balance Shares costs associated with treatment between different operations, but Logistical problems of transporting large volumes of ww within great distances In Greece problematic wastewaters: Cattle manures (CM): > farms Pig manures (PM): > farms Five different mixtures were tested CM PM TOPW

21 Anaerobic co-digestion - Experimental procedure Experimental procedure Duplicate batch systems in 118 ml glass vials Continuously system: 4 digesters of 50 L volume Thermophilic (55 o C) and mesophilic (35 o C) conditions Parameters monitored in the bioreactor ph TKN C/N ratio TOC/VFAs/Total phenols TS/VS Biogas analysis

22 Anaerobic co-digestion - Results Batch system: Start-up time 3 days Thermophilic conditions Biogas production nearly over within the first days (highest value for CM:PM:TOPW 35:35:30). ). If the HRT is sustained for 21 days VFAs decreased from 750 mg/l to 0 VS reduction 70-77%. TOC reduced by more than 80% Mesophilic conditions Biogas production continued until day 21 (slower metabolism, highest value for CM:PM: TOPW 50:25:25). VFAs decreased from 750 to 100 mg/l. VS reduction 63-70% TOC reduced by more than 70% Continuous system: Start-up tine 21 days The methane production in the mixture CM30/PM30/ TOPW 40 under thermophilic conditions was only slightly (7-15%) higher compared to the mesophilic ones, probably due to accumulation of salts within the digesters. NaCl from TOPW into the digesters resulted in osmotic pressure change and damaged the microbiological process. Even if anaerobic digestion of industrial wastewaters is, mainly due to the lower costs, performed under mesophilic temperatures, in the case of combined treatment of CM, PM and 40% TOPW, thermophilic digestion also by slightly higher methane recovery, is preferable, since the greater mobility of the microorganisms makes the whole process more stable.

23 Conclusions ΙΙ Co-digestion of CM, PM with TOPW results to more than 50% increase on methane production compared to single cattle manure fed system. If OMW will be co-digested with manures the biogas yield can be increased by 150%. (Angelidaki et al.) For all parameters monitored, thermophilic digestion provided better removal efficiencies. 40% addition of TOPW in anaerobic digestion systems could be considered as safe for the process, however it could lead to suboptional growth of microorganisms which can result in lower methane recovery related to the potential of the wastewater mixture.

24 Thank you very much for your attention