Fresenius' Journal of Fresenius J Anal Chem (1991) 339: 669-672

Analysis and anaerobic degradation of wool scouring and olive oil mill wastewaters

@ Springer-Verlag 1991

Bruno Rindone 1, Vineenza Andreoni 2, Alberto Rozzi 3, and Claudia Sorlini4 1 Oipartimento di Chimica Organica e Industriale, Universitfi di Milano, Via Venezian 21, 1-20133 Milano, Italy 2 Istituto di Microbiologia e Industrie Agrarie, UniversitA di Torino, Via Giuria 15, 1-10126 Torino, Italy 3 Istituto di Ingegneria Sanitaria, Politecnico di Milano, Piazza Leonardo Da Vinci, 1-20133 Milano, Italy 4 Dipartimento di Scienze e Tecnologie Alimentari e Microbiologiche, Universit/t di Milano, Via Celoria 2, 1-20133 Milano, Italy

Summary. Two types of fatty industrial wastewaters, wool scouring effluents (WSE) and olive oil mill effluents (OME) were analysed (lipids, phenols and COD), and were then treated anaerobically in laboratory-scale fixed bed filters. Approximately 50% of the organic compounds in both wastewaters was degraded at two days of hydraulic residence time. A higher biogas production was obtained when using OME rather than WSE. This experimental study confirmed that anaerobic digestion can be considered as a roughing treatment in a multi-step process for industrial fatty wastewaters.

Introduction

Treatment of fatty wastewaters is a difficult technological and environmental problem because the concentration of these effluents is normally fairly high and because they can contain organic compounds which are difficult to degrade by microorganisms. Therefore single stage biological processes cannot be used to reach effluents standards and multistep treatments are required. This needs a careful monitoring of the efficiency of the individual steps.

Wool scouring effluents (WSE) and olive oil mill effluents (OME) are two examples of fatty industrial wastewaters which give major problems in this respect. The practical difficulties of reaching the removal efficiency required by local regulations has led wool scouring companies in Germany and Great Britain to close some of their plants. In Italy it postponed the enforcement of the Anti-pollution Act with reference to olive oil mill effluents. Since both wool and olive oil industries are important in Europe, the treatment of their wastewaters is a major problem today.

WSE contain appreciable quantities of organics as fats, suspended solids and surfactants. The COD can be larger than 60 g/1 and it is not readily biodegradable.

Several treatment processes have been tested on WSE: acid destabilisation (of the emulsion) followed by floccula- tion and clarification [1], aerobic lagooning [2], activated sludge process [3], a combination of anaerobic and aerobic biological treatments [4] and enzymatic pretreatment (hy- drolysis) followed by anaerobic digestion [5].

Wastewaters (vegetation and washing waters) produced by olive oil mills (OME) are among the strongest industrial effluents (COD up to 200 g/l). Treatment and disposal of OME is an important problem all over the production area of olive oil, i.e. the Mediterranean area.

Offprint requests to. B. Rindone

Previous studies indicate that OME contain many organic compounds, and among them are fatty acids [6], phenylpropanoic compounds [7], non-ionic surfactants and phthalates [8] and that they can be partially degraded by anaerobic treatment, especially after storage for some months [9].

Several components of these industrial effluents are rather resistant to biological degradation, in particular, phenylpropanoic compounds [10] and long chain fatty acids [11]. Their anaerobic degradation has been studied separately.

Selecting metabolic and molecular indicators of the bio- chemical degradation pathways of these industrial effluents could help to monitor treatment performance and to select the most appropriate process configuration and operating conditions for the treatment of OME and WSE. Moreover, this could help to focus the attention to those components whose concentration before and after treatment may reflect the efficiency of the whole process.

In this paper analytical methods to be used in order to monitor the efficiency of anaerobic treatment of OME and WSE and related results are described. The wastes were degraded in a laboratory-scale upflow fixed bed digester.

Materials and methods

The laboratory-scale anaerobic fixed bed upflow reactor used in this study is made of a perspex cylinder with the following characteristics: internal diameter: 15 cm; height: 100 cm; total volume: 15 dm 3. Two different media were used to fill the anaerobic filter. Cubes of macroreticulated expanded polyurethane (Recticel, Wetteren, Belgium); porosity: 45 pores per inch; 2.5 cm size, were used as packing material when the reactor was fed with WSE. In this case the useful volume was /3 dm 3.

For OME treatment, wood chips were used as support medium. The main characteristics of the packing material are: apparent specific weight 250 kg/m3; specific surface 538 m2/m 3. In this case the useful liquid volume was 9.5 dm 3 .

The reactors were installed in a thermostated room at 30°C and a gas holder (foating bell) at 30°C and 130 Pa was used to collect and measure the biogas output. The feedstock was delivered by a peristaltic pump which opera- tion was controlled by a timer.

As already mentioned, two different wastewaters were tested: fresh WSE (obtained from Pettinatura Italiana, Vigliano Biellese, Italy) were fed to the digester after addition

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of 1.5 g/1 of NH4C1; 0.35 g/1 of K2HPO4; 2 g/1 of KH2PO4; 0.1 g/1 of MgC12 - 6 H20; 0.1 g/1 of yeast extract. Concen- trated HC1 was used to neutralize the waste prior the diges- tion process. Average COD of this wastewater was 35 g/1.

OME (obtained from the Istituto di Ricerca sulle Acque, Bari, Italy) was also used as alternative feed. They were first diluted with tap water and neutralised with 4 g/1 of NaHCO3 to obtain an average COD of 4 5 - 50 g/1.

In both cases the hydraulic residence time (measured on the useful volume) was kept at 48 h. Performance of the digester was determined by monitoring pH, gas production and COD removal efficiency. COD determinations were carried out according to Standard Methods [12].

The gaschromatographic analyses of the organic components were carried out according to the following procedures: 15 ml samples of the wastewaters were diluted with 50 ml of distilled water, the pH was adjusted to 7, then they were extracted with three 50 ml portions of redistilled ethyl acetate. The organic extracts were separated by cen- trifugation, collected, dried over sodium sulphate and the

solvent was eliminated by evaporation at reduced pressure at 40°C. The aqueous phase was adjusted to pH 2 and the extraction procedure was repeated. The residues thus obtained were dissolved in I ml of redistilled methanol, 2 ml of an ethereal solution of diazomethane were added and the resulting solution was left overnight at room temperature in order to convert carboxylic acids into methyl esters and phenols into methyl ethers. The samples were then injected in a Varian Vista 6000 gaschromatograph equipped with a SE 30 4% 25 m capillary column and operating as follows: carrier gas: nitrogen; temperature of the split-splitless in- jector: 230° C; temperature of the flame ionisation detector: 270 ° C. Oven temperature: 120°C for 1 min, then increased to 250°C with a gradient of 6 ° C/rain, and maintained at 250°C for 10 min. The data were collected with a Varian 4270 integrator.

Gaschromatography-mass spectrometry was performed with a VG 7070 EQ instrument operating both in the electron impact mode at 70 eV and in the chemical ionisation mode (ionising gas 2-methylpropane).

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Fig. 1. Gaschromatographic analysis of methylated WSE. Straight chain even carbon atom number saturated fatty acids: z~X tetradecanoic acid, methyl ester; Z~x hexadecanoic acid, methyl ester; Z~x eicosanoic acid, methyl ester; z~x docosanoic acid, methyl ester; Z~x tetracosanoic acid, methyl ester; ,/~ hexacosanoic acid, methyl ester; z~x octacosanoic acid, methyl ester. Straight chain even carbon atom number unsaturated fatty acids: z~X 9-octadecenoic acid, methyl ester. Branched chain even carbon atom number saturated fatty acids: a) Branching

at C-(-2): Z~X tetradecanoic acid, 12-methyl-, methyl ester; Ax6x hexadecanoic acid, 15-methyl-, methyl ester; b) Branching at C-(- I): @ 2 2

hexadecanoic acid, 17-methyl-, methyl ester; & octadecanoic acid, 17-methyl-, methyl ester. Straight chain odd carbon atom number saturated

fatty acids: [ ] pentadecanoic acid, methyl ester; [ ] heptadecanoic acid, methyl ester; [ ] heneicosanoic acid, methyl ester; ~}] tricosanoic acid, methyl ester; [ ] pentacosanoic acid, methyl ester. Branched chain odd carbon atom number saturated fatty acids: [~ pentadecanoic acid, 14-methyl-, methyl ester; ~ heptadecanoic acid, 16-methyl-, methyl ester. Straight chain even carbon atom number saturated fatty

alcohols: z~x l-docosanol; Z~ 11tetracosanol; Z~X 1-hexacosanol. Straight chain odd carbon atom number saturated fatty alcohols; ~] 1-

heptacosanol. Steroids: ~ 0 0 0 0 cholesta-4,6-dien-3fl-ol; ~ cholesta-5-en-3fl-methoxy; ~ cholesta-5-en-3fl-ol; ~ cholesta-3,5-dien-7-one. Others. @ eicosene; @ dioctyl phtalate

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Fig. 2. Gaschromatographic analysis of methylated OME. Straight chain even carbon atom number saturated fatty acids: z~ dodecanoic acid, methyl ester; Z~x tetradecanoic acid, methyl ester; z~xhexadecanoic acid, methyl ester; z~X octadecanoic acid, methyl ester. Straight chain even carbon atom number unsaturated fatty acids: z~x octadecenoic acid, methyl ester. Others: @ dibutyl phthalate; @ dioctyl phthalate; @ ethyl bis(oxyethyl; ethanol; @ methyl dimethoxy benzoate

Results and discussion

Raw WSE and OME were analysed by GLC-MS after sol- vent extraction and methylation with ethereal diazomethane. The composition is quite different, as it could be expected taking into account that the former contain animal fats while the latter are derived from vegetal products.

The GLC-MS analysis of WSE (Fig. l) after solvent ex- traction and diazomethane derivatisation showed the pres- ence of several even carbon atom number straight chain saturated aliphatic fatty acids such as the C-14, C-16, C-20, C-22, C-24, C-26 and C-28 congeners. Some odd carbon atom number straight chain saturated fatty acids were also present. They were the C-15, C-17, C-21, C-23 and the C-25 acids. Several branched chain saturated fatty acids were also found. They had C-15, C-16, C-17, C-18 carbon chains and a branching at C-(~o-1), and C-14 and C-16 carbon chains and a branching at C-(~o-2). The C-t8 unsaturated acid was also present. Also some straight chain alcohols such as the C-22, the C-24, the C-26 and the C-27 compounds were found. Terpene-like compounds were cholesterol, its methyl ether and two cholestadienes.

GLC-MS analysis of OME after solvent extraction and derivatisation with diazomethane showed a marked difference in the composition (Fig. 2) relative to that noted for WSE. Here, even carbon atom number straight chain fatty acids were essentially present. They were the C-12, C-J4, C-16, and C-18 acids. Moreover, an unsaturated

C-18 fatty acid, oleic acid was the major acidic component, and was accompanied by several other mono- and polyunsaturated C-18 fatty acids. A further important feature of OME was the presence of considerable amounts of phenolic material of the C-7 and C-9 phenylpropanoic family, known to be rather resistant to biological degrada- tion. Also an ethoxylated alcohol used as non-ionic surfactant was present.

WSE and OME were degraded anaerobically in the fixed bed reactor, the former without and the latter after dilution with tap water. Digestion performance was monitored by daily determinations of pH, COD and biogas production.

The results from WSE are shown in Fig. 3. COD removal efficiency was in the range 4 5 - 5 5 % , and specific biogas production was in the range 0.15-0.25 m3/kg removed COD. Methane was 89% and carbonic anhydride 9% in the biogas.

From these experiments, the anaerobic degradation re- sulted to be a reliable method to be used as the first stage of a multistep procedure, giving removal of one half of the COD with good biogas production and with a limited pro- duction of biomass.

These results were in line with those that suggest anaer- obic treatment as a good primary treatment in high organic loaded wastewaters [13].

A similar experiment was performed using OME for feeding the digester.

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The in t roduct ion in the digester of O M E diluted 1:1 with tap water was required. The limited amount o f O M E produced in olive oil mills allows this di lut ion without major problems. The same parameters as before were moni tored. They are repor ted in Fig. 4. COD removal efficiency was again in the range of 45 - 55% with a residence time of 48 h. Biogas product ion was rough higher than that observed in WSE: it was in the range of 0 . 3 - 0.6 m3/kg removed COD. Content o f methane was 84% and that of carbonic anhydr ide 13 % in the biogas.

Thus, the anaerobic degradat ion o f O M E had a COD removal efficiency very similar to that of WSE, with a higher recovery o f energy due to a higher specific biogas produc- tion. Again, anaerobic degradat ion may be used as the first step of a mult is tep degradat ion procedure.

The effluents from the digester were analysed after sol- vent extract ion and diazomethane derivatisation. The most prominent difference from the start ing wastewater was the lowered amount o f unsa tura ted fatty acids. This parallels the finding that acetogenic bacteria are able to reduce isolated fat ty acids [14] and that an anaerobic consor t ium was able to reduce the double bonds of oleic acid and other unsatura ted fatty acids and of phenylpropenoic compounds [10].

We conclude that the hydrogenat ing abil i ty o f an anaer- obic t reatment could be a good molecular moni tor of its efficience, to be used as a quali ty control of the effluent of an anaerobic p lant in mult is tep processes.

Acknowledgements. This work was supported by a CNR grant (Pro- getto Finalizzato Energetica). We thank our students Dr. L. Calvosa,

Dr. D. Daffonchio, Miss A. Pennacchio, Mr. G. Benedetti, Mr. R. Lucini and Mr. A. Cremonesi.

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Received January 10, 1991