The role of the cesspool is generally to collect some of the environment will cause pollution of harmful solutions, so the impermeability requirements are relatively high. Paper mill cesspools, power plant regulating pools, chemical plant cesspools most of the concrete structure of the pool, by the uneven settlement of the foundation and other factors, the rigid structure will have varying degrees of cracking and leakage, often need to be repaired, but also cause serious pollution to the environment.
The water in the cesspool mainly contains acidic and alkaline, toxic and harmful substances, and temperature changes will occur in the process of water treatment. Therefore, the bottom of the cesspool seepage control should not be delayed! Geosynthetics geomembrane and other new environmentally friendly seepage control materials came into being!
Sewage pond seepage control why HDPE membrane
Currently, the pool of sewage treatment plants usually use reinforced concrete and soil pool structure type, but these structural types exist in the high cost of engineering, construction process is complex, long duration, easy to crack and other defects, especially when applied to some of the larger volume of the pool, these defects are more prominent.
At the same time, the earth pool structure type of its own seepage control performance is poor, and HDPE geomembrane has a good seepage control performance, just to make up for this defect. But it is not completely independent, but can be assisted with reinforced concrete structure, in order to achieve better results. Moreover, HDPE geomembrane has the advantages of low cost, good impermeability, good chemical stability, good UV aging resistance and resistance to rodent and microbial infestation, and at the same time avoiding the risk of seepage, so it is suitable for all types of wastewater treatment tanks.
What seepage control membranes are used in sewage treatment ponds
In sewage treatment seepage control and other environmental protection projects, HDPE membranes are mainly used in the following projects:
Sewage treatment pond seepage control
All kinds of wastewater storage pond seepage control
Chemical precipitation ponds, reaction ponds, heap leaching pond seepage control
Hazardous liquids collection pond
Power plant regulation pond seepage control
Power plant regulating pool seepage control
Landfill leachate collection pool seepage control
Paper mill sewage pool seepage control
Large sewage pipeline lining corrosion control
Remediation of sewage pool leakage structure, renovation, repair
Sewage pool seepage control and anti-corrosion project base requirements
The air temperature should be 5 ℃ or more in general, when the low-temperature geomembrane should be Tighter, high temperature geomembrane should be relaxed.
The wind is below grade four.
When the temperature is too low, more than four winds and rain and snow generally should not be constructed.
In windy weather, the wind affects the construction of geomembrane, the HDPE membrane to be welded should be pressed firmly with large stones or sandbags.
Measurement of the size of the membrane before cutting
HDPE impermeable membrane cutting, by measuring its size, and then according to the actual cutting, in the membrane paving between the membrane and the membrane of the lap width of not less than 100mm, so that the seams are arranged in the direction of parallel to the foot of the maximum slope line, i.e., along the direction of the slope arrangement.
HDPE geomembrane laying
Before the laying of the film on the HDPE membrane appearance quality of the package inspection, record and repair the mechanical damage and production trauma, holes, folding and other defects have been found.
Laying HDPE membrane should strive to minimize the weld, under the premise of quality assurance, try to save raw materials. It is also easy to ensure quality.
Special lot lap
Usually in the corner and deformed lots, should be the seam length as short as possible.
Except for special requirements, in the slope greater than 1:6 slope from the top slope or stress concentration area within 1.5 meters, try not to set up welded seams.
HDPE seepage control membrane in the laying, should avoid artificial wrinkles, the temperature is low, should try to tighten, lay flat.
Pauses for attention after the completion of paving
HDPE membrane paving is completed, should minimize walking on the membrane surface, moving tools, etc., any object that can cause harm to the HDPE membrane should not be placed on the membrane or carried on the membrane walking, in order to avoid accidental damage to the membrane.
HDPE geomembrane welding technology
Welding channel lap width: 80~100mm; plane and vertical natural folds respectively: 5%~8%; reserved expansion: 3%~5%; edges of the remaining amount of material: 2%~5%.
Hot fusion welding working temperature 280~300℃; traveling speed 2~3m/min; welding form double welding pass.
Broken parts of the repair method, cut the same specification of the material, hot melt adhesive repair, polyethylene adhesive sealing.
HDPE membrane anchoring
Many methods of anchoring: trench anchoring, nail anchoring, expansion bolt anchoring, pre-embedded parts fixed. Sewage tanks are usually fixed with pre-embedded parts or expansion screw compression bars.
Pressure strip width of not less than 2cm, the thickness shall not be less than 2mm, expansion bolt spacing should not be greater than 600mm, pressure strip should be exposed to anti-corrosion measures.
Bolt diameter is not less than 4mm, the spacing is not greater than 0.5mm, construction, first prepared sandbags will be placed in position of the membrane temporary fixed to prevent the wind will be blown HDPE membrane displacement, and then expansion bolts anchored.
If the pool has been buried in the buried parts, you only need to use extrusion welding machine to weld the membrane to the HDPE buried parts.
HDPE membrane construction precautions
Hot air gun, sander and welder trailing power cord in the use of the process, must be maximized away from its working parts, so as not to damage the wire leakage.
In addition to hot air welding, the mouth of the hot air gun in any case shall not be in contact with the HDPE membrane surface, and as far as possible away from the membrane surface, the human body, machinery and other objects.
The welder shall not be placed directly on the HDPE membrane surface when it is not in use, but shall be placed on a stand or sandbag belt.
The film cutter knife after use, should immediately take back the blade in the knife box.
All kinds of temporary small tools used in the field, after use, should be put into the tool box in time.
It is strictly prohibited to discard the solder material taken off from the gun head of extrusion welding machine directly on the geomembrane surface.
Smoking is prohibited at the construction site of HDPE geomembrane, and it is not allowed to wear shoes with iron nails or high heeled hard-soled shoes to walk on the surface of the membrane, and it is not permitted to engage in all activities that may damage the finished geomembrane.
Geomembrane testing and repair
The test is carried out in three steps, i.e. visual inspection, inflation test and damage test.
Visual inspection is mainly on the laying of the geomembrane appearance, weld quality, T-welding, substrate debris and other detailed inspection, all the construction workers on this work should be carried out in all the construction process.
In addition to visual inspection, 50㎝50㎝ square grids should be taken for vacuum inspection for single weld and T-junction and repair point, vacuum pressure is greater than or equal to 0.005MPa, keep 30s, soap solution is qualified if it doesn't blister
Appearance inspection, found that there are defects such as eyelet on the membrane surface, and leakage of weld, false weld and breakage in the process of welding, etc., it should be repaired in time by using fresh base material, and the repair scar is more than one side of the membrane. Repair, patch scar each side over the broken parts of 10-20cm.