Landfill Leachate Storage Tanks for Aggressive Leachate Service
Created on 09.03
Landfill Leachate Storage Tanks for Aggressive Leachate Service
Landfill leachate is one of the more aggressive liquids a storage tank will ever hold: pH can run strongly acidic to alkaline, chloride and ammonia are high, and the fluid carries a heavy biological and sulphide load. A glass-fused-to-steel tank handles it because the enamel layer is fused to the steel at 820–930 °C, is 0.25–0.45 mm thick, inert across pH 1–14, and spark tested at 1500 V DC after assembly. The remaining corrosion risks sit outside the lining: the gasket, the bolted joint, the roof gas space and the external coating below the foundation line. Design the lining, the gasket and the vent as one system and the tank reaches its 30-year design life without a lining replacement.
Leachate storage is rarely glamorous work, and it is almost always late in the project: the cell is filling, the collection system is producing, and a tank has to hold the surplus before it can be treated or evaporated. The fluid arrives with a chemistry that a design engineer has not measured that month, or sometimes has not measured at all, and it arrives with a solids fraction that settles. This article covers the real corrosion picture in leachate service, the tank construction options that survive it, the geometry choices that decide how long the tank can hold a full load through a wet period, and the inspection list that keeps it serviceable.
What the fluid actually attacks
Leachate corrodes through chemistry and through solids, and the two failure paths are different. Chemically, young leachate from a fresh cell is acidic and rich in volatile fatty acids and hydrogen sulphide; mature leachate drifts alkaline with high ammonia and chloride. Both ends of that range sit inside what glass-fused-to-steel accommodates, since the enamel is inert across pH 1–14, but the gas space above a stored leachate charge is where most of the damage happens if it is unmanaged: hydrogen sulphide in a humid head space attacks bare steel and even attacks a coatings system that was chosen for immersion duty rather than for vapour duty.
Mechanically, the solids fraction settles and holds water against the lower shell plates, and the liquid line sees the highest concentration of dissolved solids and the strongest localised attack. That is also the band where a coating defect becomes active rather than cosmetic. Glass-fused-to-steel removes the coating from that equation: the enamel is fused to the steel, so the failure modes become delamination of the enamel from the base and pinhole defects, both of which are detected in the factory by a 1500 V DC spark test rather than discovered in year five. Where a project needs a coated steel option instead, fusion-bonded epoxy applied to a 180–280 µm film under AWWA C550 with more than 4000 hours of salt spray resistance is the comparable route, and it is a powder-fused film rather than a painted film.
Tank construction for leachate
A leachate tank is a low-pressure container, and the specification has to say so before anyone calls it a pressure vessel. The shell operates at atmospheric pressure with a vent; the pressure boundary is the roof system and the relief setting, typically only a few kilopascals. Getting that classification right at the tendering stage avoids a code path that adds cost without adding safety. If a project genuinely requires a pressure vessel, that vessel is designed to the specification and codes agreed in the contract, and it is a separate procurement from the leachate storage shells.
Construction type follows site logistics as much as chemistry. A welded stainless or carbon steel shell is a monolithic alternative and needs non-destructive examination of the field welds; a bolted glass-fused-to-steel shell arrives as flat panels of roughly 1.2 m width, assembles with gasketed joints and 8.8-grade bolts, and needs no field coating of the interior. Large diameter matters here because leachate storage volume is often needed quickly and in quantity: single bolted tanks are supplied up to 60,000 m³, and a large-diameter shell gives volume without a taller structure that would complicate the ring beam and the wind case. A tank that can later be raised with additional panels is a useful hedge when the fill rate is uncertain.
Geometry, level control and the wet-period buffer
The volume question is really a question about the worst wet period the site can face. Leachate generation peaks after heavy rainfall and in the early years of a cell, and the storage must cover the gap between generation and discharge capacity, including any closed period for the treatment works. Model generation against discharge over the worst month and the required volume falls out; then the diameter and height follow the same 0.785 times D² times H relationship used for any circular tank, with freeboard added for foam, sediment and the expansion case. Operational level control matters just as much: an overflow or a high-level trip with an alarm to the site control room is what turns a storage tank into a containment asset rather than a liability.
Below the tank, the foundation is the part that is usually under-specified. A bolted tank wants a ring beam or a pad with a controlled settlement difference and an anchor pattern matching the panel holes. A leachate tank on a landfill cap or a prepared cell has the additional requirement that the pad itself must not breach the liner system, which means the tank is normally sited on a separate prepared pad within the site rather than directly on the cap. External corrosion protection for the shell below grade, and for the bottom plate where there is no internal lining on a welded design, belongs in the same scope.
Technical Specification
Parameter | Typical Value / Range | Note |
Enamel fusion temperature | 820–930 °C | one thermal fusion cycle to the steel |
Enamel layer thickness | 0.25–0.45 mm | 1500 V DC spark test after assembly |
Enamel layer compressive strength | above 3,450 N/cm² | rated for the enamel layer |
pH resistance of enamel | 1–14 | covers acidic young and alkaline mature leachate |
Interior surface roughness | Ra < 0.8 µm | low deposit hold-up on the wall |
Design life | at least 30 years | under the specified chemical service |
Panel width | about 1.2 m | modular bolted panel, ships flat |
Bolt grade | 8.8-grade bolts | corrosion-inhibited bolted joint |
Gasket | EPDM common, verify against pH and temperature | ages in service, re-torque on the schedule |
Pressure class | atmospheric to low pressure | roof and vent define the boundary |
FBE alternative | 180–280 µm, above 4000 h salt spray | AWWA C550, coating route instead of enamel |
Inspection and the items that will actually fail
A leachate tank inspection programme is short and specific. Externally: the coating above and below the foundation line, the bolt heads and the joint gasket exposed at each vertical seam, and any settlement cracking at the ring beam. Internally, at the first-entry opportunity: the enamel for pinhole or delamination, with a spark retest after any panel that has been opened; the bottom plate where sediment has held water; the inlet deflector and the outlet nozzle; and the level gauge. Mechanically: the vent and any gas detection in the head space, the manway gasket, and the high-level alarm.
That last item deserves emphasis. Leachate tanks fail in the public record when they overflow, and the overwhelming cause is not lining failure but level management: no functioning high-level alarm, an operator working a part-time shift, and a discharge connection that was assumed. Specifying a level instrument with a remote alarm, a manual override valve and a defined discharge protocol costs less than a single spill report.
Project Case
Project | Location | Product | Capacity | Scope |
Leachate tanks, two units | China, Beijing | GFS tanks | 9,682 m³ | φ16.23 × 23.4 m, supply and supervision |
Welded leachate tank | China, Hebei | welded steel tank | leachate service | supply and field welding |
Large-diameter water tank | Namibia | GFS tank | 44,900 m³ | supply and supervision |
Chemical wastewater tank | China, Zhejiang | GFS tank | 11,613 m³ | φ24.45 × 19.8 m, supply |
Center Enamel Engineering Capability
Center Enamel (Shijiazhuang Zhengzhong Technology Co., Ltd) has designed and fabricated bolted storage tanks since 2008. As the first glass-fused-to-steel (GFS) tank manufacturer in China, the company holds close to 200 enamel-related patents, produces roughly 300,000 enamel-coated steel plates a year, has completed more than 30,000 installed projects and supplies its tanks to over 100 countries. The new 150,000 m² production base was added to raise output capacity, and single tanks are supplied up to 60,000 m³. Manufacturing runs under ISO 9001 and ISO 45001, with product certification including NSF/ANSI 61, WRAS, FDA, LFGB, CE (EN 1090), ISO 28765, FM, BSCI and EUROCODE, and design referenced to AWWA D103-09, AWWA C550 and NFPA where the application requires it.
For leachate service the relevant part of that is the enamel chemistry envelope, the large-diameter shell experience needed to hold a wet-period buffer in one vessel, and the gasket and vent selection that keeps the boundary intact when the fluid swings from acidic to alkaline between the young and mature phases of a cell.
Frequently Asked Questions
Q1: Can a glass-fused-to-steel tank hold raw landfill leachate?
A1: Yes, within the enamel's pH 1–14 envelope, which covers both the acidic young leachate and the alkaline mature leachate. Confirm the gasket material and the gas space treatment, because those are outside the lining's control.
Q2: Is raw leachate storage a pressure vessel?
A2: No, it is a storage tank operating at atmospheric or low pressure. The vent and relief device set the pressure boundary at a few kilopascals. Pressure vessels, where the process needs them, are designed to the specification and codes agreed in the contract.
Q3: How much volume should a leachate tank have?
A3: Size it against the worst wet period: the volume needed between peak generation and available discharge capacity, plus freeboard. The generation curve of a landfill cell rises steeply in the first years, so the early requirement is usually larger than the steady-state one.
Q4: What is the difference between a leachate storage tank and a welded steel tank here?
A4: Storage is typically lower cost and faster to site with a bolted enamel shell; a welded shell is monolithic and needs field weld examination. The choice is often driven by site access, by the required volume and by whether the interior must be inspected and cleaned.
Q5: Does the enamel need re-spark testing in service?
A5: A spark test is done after assembly and after any panel is opened and replaced. In service the enamel is inspected visually; a pinhole or delamination at the liquid line is the condition that warrants a local retest.
Q6: What about the tank foundation on a landfill site?
A7: The tank should sit on its own prepared pad with controlled settlement, not directly on the cap liner, so that a leak or a spill is contained on a non-breaching surface. External coating below grade and under the anchor pattern is part of the scope.
Q7: Can the tank grow if the landfill fills faster than planned?
A8: On a bolted shell yes. Extra panels raise the height or additional bays widen the diameter, and specifying the pad for the larger footprint at the start costs little compared with adding a second tank later.
Landfill leachate storage tanks are won or lost on three things: an enamel lining that is inert across the full pH swing, a gasket and vent system that is selected with the fluid rather than by habit, and a level control and discharge protocol that prevents an overflow. The shell material is the easy part once the chemistry is defined; the boundary items are where the maintenance budget goes.
Send us the leachate analysis, the generation curve, the discharge capacity and the site pad condition, and we will return a tank sizing, a lining and gasket recommendation, and the technical file package.
Talk to an Engineer
We will review your chemistry and your generation data before recommending a product. Share the pH range, chloride and ammonia figures, the required storage volume and the pad condition, and you will get a written selection, the inspection list and the drawings for review. Engineering first, no pressure.
WhatsApp