Treatment of High Strength Industrial Effluents Using Levapor Bio Carriers for the immobilization of Biomass
Biotreatment of Industrial EffluentsbyLEVAPOR BIOFILM TECHNOLOGIESVarious industrial production activities require large quantities of water fordifferent purposes, e.g. for washing of raw materials and final products, asmedium for reactions, for cooling, etc. During these processes water streamsget in contact with different organic and/or inorganic materials and becomepolluted. Unlike municipal sewage, industrial effluents are polluted withdifferent pollutants with changing quality (composition) and quantity, wherebymany of them are only slowly or non biodegradable and also sometimes toxic(colours, additives, biocides, etc.).Fig. 1 Untreated industrial effluentsWhile municipal treatment plants can be designed on basis of numberpopulation and some further indicators, industrial plants do require still serious preliminary work, also practiceoriented research and test work, resulting in tailor-made-solutions, biodegradability of pollutants and establishment of processparameters represent the main targets. Since 1975 we have conducted tests on biodegradation and bioprocessoptimisation, respectively process designs for industrial and municipalclients, developing new, innovative bio treatment technologies, applied inseveral industrial branches, like:
Chemistry, agrochemicals and pharmaceuticals, Fermentation technologies (antibiotics, enzymes, breweries, etc) Petrochemicals and refineries, Pulp and paper, textile and at least Food industry: sugar mills and beverages. Biological removal of pollutants depend different factors:Chemical structure –organic acids, alcohols, aldehydes, amines are easilydegradable, while pollutants containing two or more methyl or nitro groupsshow remarkably slower degradability. Structure may decrease solubility,respective bioavailability of a molecule, hinder microbial attacks, but alsoinhibit the degradation process.Waste water matrix- concentration and quality of all pollutants do influencecomposition of biomass of sludge flocs, while increasing salinity lowersfood uptake of biomass.Microbial strains relevant for degradation of certain pollutants must bepresent in the bioreactor.Milieu conditions - pH, temperature, redox potential, etc. are also essentialfor microbial activities.However, by applying methods of modern biotechnology, even these pollutantscan be degraded biologically both in laboratory and also in practice.Key factors of their removal are Presence of active, specific active biomass in required quantity, Optimal conditions for the efficient and stable degradation processes, Bioreactors , ensuring optimal conditions, respectively Retention and protection of relevant active microbial strains. Microbial strains represent mixtures of single strains, able for breaking differentchemical bounds. They show often slow growth rates and weak flocculation,resulting in their wash-out from bioreactor and in unstable bioprocesses.Optimal process conditions and parameters can be determined in lab scaletests, under anaerobic, microaerobic and aerobic conditions.Immobilisation of biomassRetention of specialized biomass in bioreactor and their protection from toxic,inhibitory effects can be achieved by fixation of microbial cells on adsorbing,
porous LEVAPOR carrier, generating highly active biofilms resistant to inhibitorsand enabling stable processes (Fig. 2). Positive effects of this method have beenproven by adequate biotests under aerobic and anaerobic conditions.Fig.2 LEVAPOR-carrier: cross section (left) and colonised by biofilm ofanaerobic bacteriaDue to high adsorbing capacity and porosity of LEVAPOR carrier hazardous, inhibiting pollutants become adsorbed on carrier surface,resulting in remarkably lower inhibitory effects in the liquid phase and faster microbial colonisation and generation of active biofilm takes place,resulting in 9conc.(m M)87 2-CA susp.org.6 adsorption onCl-released5LEVAP OR43212-CA-immobil.240 hr0 hr.01 2 3 4 5 6 7 8 9 10 11 12 13 14 15Fig. 3 Biodegradation of 1000 mg/L (7,8 mM) of 2-Chloroaniline (2-CA) bysuspended, and on LEVAPOR fixed microorganisms1(1Prof.Streichsbier, et al., University of Vienna, Austria)
- higher resistance of microbial cells in biofilm against toxic effects,- higher process performance; degradation of adsorbed pollutants and- biological regeneration of adsorbing capacity of LEVAPOR (fig. 3).Effects of biomass immobilisation were investigated in batch tests for biodegra-dation of 1000 mg/L of toxic 2-Chloroaniline (2-CA) under aerobic conditions.While suspended microorganisms became inhibited by 7.8 mM of 2-CA,additionof LEVAPOR, followed by adsorption of 2-CA on carrier surface reduced itsconcentration (and toxicity) in liquid phase within 2 hours to 3.2 mM, enablingstart up and a quantitative biodegradation within 240 hrs of 2-CA including alsothat of the adsorbed fraction, indicated by release of Cl-ions.Nitrification of industrial effluentsis not easy because of quality and salinity fluctuations. Increased salinityresults in decreased uptake of organic pollutants and especially nitrogen,meaning lower degrees of COD- and N-elimination. Presence of even lowconcentrations of special inhibitors results often in a crash of nitrificationprocess even under continued non inhibited COD-removal.By immobilizing nitrifying biomass, negative effects of inhibitors can bereduced remarkably (Fig. 4, right: 94.5 % nitrification, versus only 28% achievedby suspended biomass, left). Both, higher resistance and higher number ofmicrobial cells fixed on carrier do contribute to stability of the process.220NH4N207195200[mg/L] 28 %180inlet160 14994,9 %outlet14012010080604020 100suspended biomass immobilisedbiomassFig.4 : Effect of biomass immobilisation on nitrification of saline and inhibitingchemical effluents (salinity:20-25 g/L,COD~1600mg/L) at Lv~ 0,25gN/Lxd.
Biodegradation of industrial pollutants under anaerobic conditionsSimilar positive effects of LEVAPOR have been confirmed also in biotests underanaerobic conditions, for degradation of 2-Chlorobenzoic acid (2-CBA), a quitestrong biocide, using methane production as indicator of degradation. Whilenon-modified-PU-foam or sintered glass carrier showed only small effects withslow generation of methane, the anaerobic reactor with LEVAPOR within fewdays after start up achieved a remarkable biogas production, completed within18 to 20 days(fig.5).Fig. 5 Effect of carrier type on biodegradation of 2-Chlorobenzoic acidunder anaerobic conditions3(3Prof.H.Sahm et al., University of Düsseldorf, Germany)Biotreatment of toxic pulp mill effluentsDue to the generation of toxic intermediates under aerobic conditions,biotreatment of several complex organic pollutants with classical activatedsludge achieves only moderate results, while anaerobic treatment performsremarkably higher removal.Aerobic treatment of pulp mill bleaching effluents, containing chlorinated toxicpollutants, resulted only 35 to 40 % COD removal, however anaerobic biofilmsfixed on adsorbing, porous carrier achieved 65 to 70 % removal and due to aremarkable conversion of pollutants, 45 to 60 % of residual COD could beeliminated in an aerobic post-treatment step (Fig. 6).
Fig. 6 Anaerobic treatment of toxic pulp mill bleaching effluents with biofilmsfixed on different carrier material: 1. LEVAPOR 2. Activated carbon3. PU-foam and 4. suspended biomass as controlLEVAPOR supported biofilm reactorsTwo reactor types are suitable for effluent treatment by LEVAPOR supportedbiofilm technology: FLUIDISED BED REACTORS or MBBR (moving bed bioreactor) asmain treatment step and BIOFILTERS for POST-TREATMENT. Most practicable are fluidised bed reactors, containing 12 to 15 vol. % LEVAPOR .Due to the low density of the cubes, even oxidation devices of existing plants aresufficient for the fluidisation of the filter bed, enabling easier upgrading of existingplants. Retention of carrier with 20x20x7 mm within preferably bottom-aeratedreactors occurs via adequate screens and/or grids.
Aerated reactorClarifierwith carrierFig. 7 Basic flow-sheet of an aerobic fluidised bed reactorinletoutletairsludgeFig. 8 Basic flow sheet of a biofilterBiofilters – may contain up to 60-70 vol.% LEVAPOR and can be operated in upflow or down flow mode. They are preferably applied for advanced treatment ofbiologically pre treated effluents, containing lower pollutant concentrations andsuspended solids. Due to lower inlet concentrations, they can be operated atshorter retention times, meaning also lower reactor volumes. Especially afterseeding with proper biomass, bio filters are very suitable for removal of micro-pollutants.
Inlet Outlet LEVAPOR-BIOFILTERParameter WWTP Outlet-LVP Eliminationg/l mg/l mg/l %Chemical site-1TOC (mg/L) 37 - 60460- 540 40-95 20- 60Aniline n.a. 40-150 4,0-10,0 90- 93Bisphenol-A n.a. 10-128 0,0- 9,0 93-100Nitrobenzene n.a. 25-130 0,5- 24,0 82 - 98Chemical site-2COD (mg/L) 3450- 4720 340- 460 190-260 25- 45Toxicity, GD n.a. 1:100- 500 1:30-250 1:50- 90Tab. 1 Removal of hazardous pollutants and toxicity by post-treatment ofdifferent effluents in aerobic biofilters using LEVAPOR-carrier140,0BPA ( g/L)120,0100,080,060,040,0in20,00,0oudays1 3 5 7 9 11 13 15 17 19 21 23 25 27 29Fig. 9 Biodegradation of bisphenol-A (BPA) in a LEVAPOR-supported biofilter aspost-treatment stepCase historiesPulp mill effluentsPilot tests, carried out after encouraging preliminary results (Fig. 6) confirmed,that anaerobic-aerobic treatment using biofilm technology represents a highlyefficient and practicable treatment method for these toxic effluents, whereasthanks to biofilms volume of anaerobic reactors could be reduced by 75 %,enabling savings of more than 10 million € ( Euros ). The plant is in operationsince 1990 (Fig.10). In order to confirm contribution of biofilm technique, duringthe start up phase only two of three methane-reactors were filled with carrier.