ANAEROBIC TREATMENT PROCESS - Institut Teknologi ?· ANAEROBIC TREATMENT PROCESS Marisa Handajani. Anaerobic…

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ANAEROBIC TREATMENT

PROCESSPROCESS

Marisa Handajani

Anaerobic Process

Methane fermentation is a versatile biotechnology capable of converting almost all types of polymeric materials to methane and carbon dioxide under anaerobic conditions.

Tahapan Proses:1. Hidrolisis

2. Asidegenesis

3. Metanogenesis3. Metanogenesis

Microorganisms : 1. fermentative microbes (acidogens);

2. hydrogen-producing,

3. acetate-forming microbes (acetogens); and

4. methane-producing microbes (methanogens) harmoniously grow and produce reduced end-products.

Anaerobes play important roles in establishing a stable environment at various stages of methane fermentation.

Reaksi pembentukan Metan:

4H2+CO2CH4+2H2O

4HCOOH CH4+3CO2+2H2O

CH3COOH CH4+CO2

4CH3OH 3CH4+CO2+2H2O

4(CH3)3N+H2O

9CH4+3CO2+6H2O+4NH3

Anaerobic Wastewater Treatment:

Anaerobic wastewater treatment is the biological treatment of wastewater without the use of air or elemental oxygen. Many applications are directed towards the removal of organic pollution in wastewater, slurries and sludges. The organic pollutants are converted by anaerobic microorganisms to a gas containing methane and carbon dioxide, known as "biogas" (see Figure 1 below). below).

Figure 1. Conversion of Organic Pollutants to Biogas by Anaerobic Microorganisms

COD Balance:In the wastewater engineering field organic pollution is measured by the weight of

oxygen it takes to oxidize it chemically. This weight of oxygen is referred to as the

"chemical oxygen demand" (COD). COD is basically a measure of organic matter

content or concentration. The best way to appreciate anaerobic wastewater treatment

is to compare its COD balance with that of aerobic wastewater treatment.

Anaerobic vs Aerobic Treatment for 1000 kg CODB/d

Parameter Anaerobic Aerobic

Power consumption (kW) 1.5 65

Net biosolids prod. (kg TS/d) 15-100 200-600

Energy produced (kW) 140 Nil

Anaerobic Process

Benefits

Less nutrients required;

System can be shut down

for extended periods

without serious

Disadvantages

Anaerobic treatment cannot

achieve surface water

discharge quality without

post-treatment; without serious

deterioration; and

Can handle organic shock

loads effectively.

post-treatment;

Reduced sulfur compounds

are produced, which need

to be properly addressed in

terms of corrosion, odor

and safety; and

Longer start-up period.

Anaerobic systems

Suspended-growth processes

systems where the bacteria grow and are suspended

in the reactor liquid 'granular' or 'flocculent

Attached-growth processes

utilize either fixed film or carrier media (which is

suspended in the liquid) for the bacteria to grow on

and attach to.

Application "High Rate"Anaerobic Treatment:

SRT HRT

Granular sludges exhibit high settling velocities and activity rates reduce reactor volume

and increase the organic loading rate depend on wastewater characteristics, system

configuration and loading condition

granular sludge is retained in the system by specially designed gas-liquid-solids separation granular sludge is retained in the system by specially designed gas-liquid-solids separation

devices,

Low Rate"Anaerobic Treatment:

SRT = HRT

effective when treating wastewaters that do not granulate well or have substances that

effect the retention of granules at high loading rates (i.e., high concentrations of fat, oil or

grease (FOG), total suspended solids (TSS), COD, salts, total dissolved solids, calcium, etc., in

the wastewater).

The net effect is that slow growing anaerobes can be

maintained in the reactor at high concentrations, enabling

high volumetric conversion rates, while the wastewater

rapidly passes through the reactor.

The main mechanism of retaining sludge in the reactor is

immobilization onto support material (microorganisms

sticking to surfaces, eg. filter material in the "anaerobic filter")

or self-aggregation into pellets (microorganisms sticking to

each other, eg. sludge granules).

Anaerobic Contact Process This process consists of a

suspended-growth reactor, with

typical loadings in the range of 0.5

to 3 kg COD/m3/d.

The lower volumetric loading rate

allows the reactor to retain non-

granular flocculent biomass and to

treat wastewaters that have higher

COD, TSS and FOG than can be

handled by high-rate processes. handled by high-rate processes.

Effective for treatingwastewaters, such as potato processing, dairy and cheese,

yeast and distillery.

The larger volume of the system means that it occupies more land area;

Retains a large amount of biomass, which gives the process more stability and

robustness than higher rate systems.

The system can operate at lower temperatures than other processes and

generates less waste sludge on a dry weight basis.

Upflow Anaerobic Sludge-Blanket Process

Influent flow is typically equalized,

neutralized and partially acidified in a

separate tank ahead of the reactor.

The influent flow is often mixed with

effluent recycle and then distributed into

the lower part of the reactor below the

sludge bed.

The upper portion of the reactor typically

has a gas-liquid-solids separator (GLSS)

that removes biogas and clarifies the

Up flow velocity : 0.6 0.9 m/h

Granules range in size

from 0.5-2.5 mm,

that removes biogas and clarifies the

effluent.

UASB UASB reactors typically require low influent TSS concentrations (< 15 percent of the influent

COD concentration) and FOG concentrations (< 100 milligram per liter (mg/l)).

Concentration from 50-100 kg VSS/m3 at the bottom, to 5-40 kg VSS/m3 in the upper part of

the reactor.

OLR: 5-15 kg COD/m3/d

Significant parameters in the UASB operation are floe diameter, microbial density, and the

structure of the gas-solid separator which effectively retains the microbial granules within the

reactor. reactor.

The criteria :

(a) selection of a suitable waste water capable of granule self-formation;

(b) operation of the reactor without mechanical agitation;

(c) start up at a relatively low COD load;

(d) use of waste water containing Ca2+ and Ba2+ and

(e) avoidance of bulking caused by filamentous microbial growth. Granule formation in a

UASB system is influenced by the growth of rod-type Methanothrix spp. which produce

spherical granules.

Anaerobic Fixed Bed Process Rasio H/d = 1-2

Nozzle umpan : 5 10 m2

Kecepatan fluida 1-2 m/h

Rasio resirkulasi 5-10

Tinggi fixed bed max 7 m; keseluruhan reaktor max 14,5 m

OLR : 5-15 kg COD/m3/d.

used for removal of soluble organics and has similar loading used for removal of soluble organics and has similar loading

limits in terms of FOG (< 100 mg/l) and TSS (< 15 percent of

COD) concentrations.

AnFB Full-scale UAFP systems (waste water can be treated at an HRT of 7.8 days with 74% COD

removal. Application of this UAFP to domestic sewage treatment using Raschig rings (2.5 cm)

as microbial supports, resulted in BOD removal of 50 to 60 % and suspended solids (SS)

removal of 70 to 80%, at an HRT ranging from 5 to 33 hours.

Selection of a medium in which microbial adhesion is greatly influenced both by SS, and the

chemical composition of the waste water, is extremely critical in UAFP systems. The effects of

physical medium characteristics, such as size and shape, on COD removal have been

investigated using modular corrugated blocks (porosity > 95%), pall rings, and perforated

spheres.

At a COD load of 2 kg/m/day, modular corrugated blocks exhibited superior behavior,

removing 88 % of COD. A comparison of COD removal for cross- and tubular-flow systems,

reveals that COD removal is 20 to 30 % greater in cross-flow systems.

In addition to plastic media, baked clay and a melted slug have also proven useful in

laboratory experiments on methanogenesis from formate, acetate, and methanol. Pumice

was used as a microbial supporter for methanogenesis from methanol-rich waste water of

the evaporate condensate from a pulp mill (COD load: 12 kg/m3/day, COD removal: 96%).

Expanded Bed Process (Fluidized)

Media: Pasir, batu bara, agregat lain

Biomassa tumbuh pada permukaan media

Konsentrasi biomassa 15.000-40.000 mg/l

Rasio H/d = 5 25

Faktor kunci: fluidization zone distribusi Faktor kunci: fluidization zone distribusihomogen dead zone dan high shear force

Tinggi fluidized bed ditentukan oleh flow rate

Untuk mengurangi kehilangan media:

stationary support-biomass separation

device pada tinggi bed maximum (minimum

1,5 m dibawah overflow)

Mengatur kecepatan fluidisasi

OLR :10 - 25 kg COD/m3/d.

AnEB Use of artificial sewage in an AFBR, resulted in COD removal exceeding 80 % at 20C, an

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