HDPE Biogas Digester

Construction method process

Advantages of HDPE fermentation tank

The covered biogas tank integrates fermentation and gas storage, and uses anti-seepage membrane materials to fully enclose the entire anaerobic pond. It has the advantages of simple, convenient and fast construction, low cost, simple process flow, easy operation and maintenance, long sewage retention time, sufficient digestion, good sealing performance, and large daily biogas production. The anti-seepage membrane material has high tensile strength, strong anti-aging and corrosion resistance, and good anti-seepage effect. It uses the waste heat of biogas to generate electricity, the film absorbs sunlight, and has good warming and insulation effects. There is an automatic sludge discharge device at the bottom of the pool, and the amount of sludge in the pool is small.

Furthermore, the membrane-covered biogas digester effectively addresses issues such as water seepage, leakage, and gas leaks caused by shrinkage and cracking due to temperature fluctuations in concrete biogas projects, as well as issues such as corrosion, pipe blockage, equipment damage, and high operating costs associated with ground-mounted steel biogas projects. This project aligns with national development strategies and the direction of national industrial development, and is currently under research and promotion by relevant departments.

Materials of HDPE biogas digester

The HDPE tank is an ultra-large sewage anaerobic reactor that uses black HDPE anti-seepage membrane material to seal the bottom and top of the oxidation pond into one. The HDPE anti-seepage membrane material has the advantages of being resistant to high and low temperatures, asphalt, oil and tar, acid, alkali, salt and other strong acid and alkali chemical media corrosion, good anti-aging performance, strong UV resistance and decomposition resistance, high anti-seepage coefficient, strong tensile mechanical resistance, can be used exposed, and long material service life. In particular, it has low cost and good performance. It is currently widely used in sewage treatment, chemical reaction tanks, landfills, etc. Membrane materials have American standards, national standards and urban construction standards. Specific parameters are shown in the test report.

Low project cost

The cost of a biogas project constructed with reinforced concrete is generally 500-700 yuan/m3, while the cost of a black film biogas tank is generally less than one-tenth of that of a steel-concrete structure, and the cost of building a biogas storage tank can be eliminated. In addition, the use of HDPE film as the tank construction material has better sealing performance than that of a steel-concrete structure.

The water temperature in the pool is less affected by the outside world

The HDPE biogas tank has a large volume and a deep depth. After the sewage enters the tank, the daily water intake is relatively small. In addition, the biogas insulation on the top of the black film biogas tank and the underground biogas tank have the characteristics of relatively constant temperature in winter. Therefore, the sewage temperature in the tank is less affected by the outside world, and it has strong resistance to the impact load of sewage.

Large amount of biogas produced

The sewage has a long retention period in the pool (more than 30 days), anaerobic fermentation is sufficient, and a large amount of biogas can be collected. The biogas production per cubic meter of sewage is 0.3-1.2m³ cubic biogas (calculated based on the pool capacity, COD content, and retention time).

Good sewage treatment effect 

The chemical oxygen demand of the aquaculture wastewater at the inlet is 9720mg/L~66400mg/L, while the chemical oxygen demand of the effluent is 862~2080mg/L, and the treatment rate is basically stable at more than 90%.

Low operating and processing costs 

The inlet and outlet sewage of the HDPE biogas tank flows by gravity, and the slag is discharged by an automatic slag discharge device. Due to the large volume of the tank, the amount of sludge produced in the tank is small, and there is no problem of blockage caused by excessive slag and sediment. Therefore, the management cost generated in normal times is very low.

HDPE biogas tank construction process

Foundation excavation：

• Construction procedures

The construction of anaerobic tank mainly includes earthwork excavation and filling, anaerobic tank, inlet and drainage pipes, etc. According to the principle of underground first and then above ground, the construction is arranged layer by layer from bottom to top. During the construction, the foundation of the anaerobic tank is started first, and then the anaerobic tank structure and underground pipeline construction are started.

• Cleaning the foundation：

First, clean the silt at the bottom of the pool and compact it, repair the concrete collapse on the slope, and make the surface relatively flat, without cracks, obvious protrusions, mud, or depressions. Clean the rubble, stones, steel bar heads and other debris in the pool.

HDPE laying (geotextile may not be laid if the bottom surface is flat)

• HDPE laying method：

The laying can be guided on site. The geomembrane should not be pulled too tight. It is better if the two ends are buried in the soil and are corrugated. Before laying the HDPE geomembrane, the relevant dimensions of the pool should be measured first, and then cut according to the actual size. The overlap width between the joints of the membrane should not be less than 150mm, that is, it should be laid along the slope direction.

Laying completed

Case display