Biotreatment of Industrial Effluents

by

LEVAPOR BIOFILM TECHNOLOGIES Various industrial production activities require large quantities of water for different purposes, e.g. for washing of raw materials and final products, as medium for reactions, for cooling, etc. During these processes water streams get in contact with different organic and/or inorganic materials and become polluted. Unlike municipal sewage, industrial effluents are polluted with different pollutants with changing quality (composition) and quantity, whereby many of them are only slowly or non biodegradable and also sometimes toxic (colours, additives, biocides, etc.).

Fig. 1 Untreated industrial effluents

While municipal treatment plants can be designed on basis of number

population and some further indicators,

industrial plants do require still serious preliminary work, also practice

oriented research and test work, resulting in tailor-made-solutions,

biodegradability of pollutants and establishment of process parameters represent the main targets.

Since 1975 we have conducted tests on biodegradation and bioprocess optimisation, respectively process designs for industrial and municipal clients, developing new, innovative bio treatment technologies, applied in several 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 easily degradable, while pollutants containing two or more methyl or nitro groups show remarkably slower degradability. Structure may decrease solubility, respective bioavailability of a molecule, hinder microbial attacks, but also inhibit the degradation process. Waste water matrix- concentration and quality of all pollutants do influence composition of biomass of sludge flocs, while increasing salinity lowers food uptake of biomass. Microbial strains relevant for degradation of certain pollutants must be present in the bioreactor. Milieu conditions - pH, temperature, redox potential, etc. are also essential for microbial activities.

However, by applying methods of modern biotechnology, even these pollutants

can 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 different chemical 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 scale

tests, under anaerobic, microaerobic and aerobic conditions.

Immobilisation of biomass

Retention 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 inhibitors

and enabling stable processes (Fig. 2). Positive effects of this method have been

proven by adequate biotests under aerobic and anaerobic conditions.

Fig.2 LEVAPOR-carrier: cross section (left) and colonised by biofilm of

anaerobic bacteria Due 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

9

conc.(m M)

8

7 2-CA susp.org.

6 adsorption on

Cl- released

5 LEVAP OR

4

3

2

1 2-CA-immobil.

240 hr

0 hr.

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Fig. 3 Biodegradation of 1000 mg/L (7,8 mM) of 2-Chloroaniline (2-CA) by

suspended, and on LEVAPOR fixed microorganisms 1

( 1

Prof.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,addition of LEVAPOR, followed by adsorption of 2-CA on carrier surface reduced its concentration (and toxicity) in liquid phase within 2 hours to 3.2 mM, enabling start up and a quantitative biodegradation within 240 hrs of 2-CA including also

that of the adsorbed fraction, indicated by release of Cl- ions.

Nitrification of industrial effluents

is not easy because of quality and salinity fluctuations. Increased salinity results in decreased uptake of organic pollutants and especially nitrogen, meaning lower degrees of COD- and N-elimination. Presence of even low concentrations of special inhibitors results often in a crash of nitrification process even under continued non inhibited COD-removal. By immobilizing nitrifying biomass, negative effects of inhibitors can be reduced remarkably (Fig. 4, right: 94.5 % nitrification, versus only 28% achieved by suspended biomass, left). Both, higher resistance and higher number of microbial cells fixed on carrier do contribute to stability of the process.

220 NH4N 207

195

200 [mg/L]

28 %

180

inlet

160 149 94,9 %

outlet

140

120

100

80

60

40

20 10

0

suspended biomass immobilised biomass

Fig.4 : Effect of biomass immobilisation on nitrification of saline and inhibiting

chemical effluents (salinity:20-25 g/L,COD~1600mg/L) at Lv~ 0,25gN/Lxd.

Biodegradation of industrial pollutants under anaerobic conditions

Similar positive effects of LEVAPOR have been confirmed also in biotests under anaerobic conditions, for degradation of 2-Chlorobenzoic acid (2-CBA), a quite strong biocide, using methane production as indicator of degradation. While non-modified-PU-foam or sintered glass carrier showed only small effects with slow generation of methane, the anaerobic reactor with LEVAPOR within few days after start up achieved a remarkable biogas production, completed within 18 to 20 days(fig.5).

Fig. 5 Effect of carrier type on biodegradation of 2-Chlorobenzoic acid

under anaerobic conditions 3

( 3

Prof.H.Sahm et al., University of Düsseldorf, Germany)

Biotreatment of toxic pulp mill effluents

Due to the generation of toxic intermediates under aerobic conditions, biotreatment of several complex organic pollutants with classical activated sludge achieves only moderate results, while anaerobic treatment performs remarkably higher removal. Aerobic treatment of pulp mill bleaching effluents, containing chlorinated toxic pollutants, resulted only 35 to 40 % COD removal, however anaerobic biofilms fixed on adsorbing, porous carrier achieved 65 to 70 % removal and due to a remarkable conversion of pollutants, 45 to 60 % of residual COD could be eliminated in an aerobic post-treatment step (Fig. 6).

Fig. 6 Anaerobic treatment of toxic pulp mill bleaching effluents with biofilms fixed on different carrier material: 1. LEVAPOR 2. Activated carbon

3. PU-foam and 4. suspended biomass as control

LEVAPOR supported biofilm reactors Two reactor types are suitable for effluent treatment by LEVAPOR supported

biofilm technology:

FLUIDISED BED REACTORS or MBBR (moving bed bioreactor) as

main 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 are

sufficient for the fluidisation of the filter bed, enabling easier upgrading of existing

plants. Retention of carrier with 20x20x7 mm within preferably bottom-aerated

reactors occurs via adequate screens and/or grids.

Aerated reactor

Clarifier

with carrier

Fig. 7 Basic flow-sheet of an aerobic fluidised bed reactor

inlet

outlet

air

sludge

Fig. 8 Basic flow sheet of a biofilter

Biofilters – may contain up to 60-70 vol.% LEVAPOR and can be operated in up

flow or down flow mode. They are preferably applied for advanced treatment of biologically pre treated effluents, containing lower pollutant concentrations and suspended solids. Due to lower inlet concentrations, they can be operated at shorter retention times, meaning also lower reactor volumes. Especially after seeding with proper biomass, bio filters are very suitable for removal of micro-pollutants.

Inlet Outlet LEVAPOR-BIOFILTER

Parameter WWTP Outlet-LVP Elimination

g/l mg/l mg/l %

Chemical site-1

TOC (mg/L)

37 - 60

460- 540 40-95 20- 60

Aniline n.a. 40-150 4,0-10,0 90- 93

Bisphenol-A n.a. 10-128 0,0- 9,0 93-100

Nitrobenzene n.a. 25-130 0,5- 24,0 82 - 98

Chemical site-2

COD (mg/L) 3450- 4720 340- 460 190-260 25- 45

Toxicity, GD n.a. 1:100- 500 1:30-250 1:50- 90

Tab. 1 Removal of hazardous pollutants and toxicity by post-treatment of

different effluents in aerobic biofilters using LEVAPOR-carrier

140,0

BPA ( g/L) 120,0

100,0

80,0

60,0

40,0 in

20,0

0,0 ou days

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

Fig. 9 Biodegradation of bisphenol-A (BPA) in a LEVAPOR-supported biofilter as

post-treatment step

Case histories

Pulp mill effluents Pilot tests, carried out after encouraging preliminary results (Fig. 6) confirmed, that anaerobic-aerobic treatment using biofilm technology represents a highly efficient and practicable treatment method for these toxic effluents, whereas thanks to biofilms volume of anaerobic reactors could be reduced by 75 %, enabling savings of more than 10 million € ( Euros ). The plant is in operation since 1990 (Fig.10). In order to confirm contribution of biofilm technique, during the start up phase only two of three methane-reactors were filled with carrier.