Landfill Leachate Treatment Routes and Concentrate Disposal: Full Parameters of HJ 564-2010 and the New Constraints of GB 16889-2024

1. The current code: HJ 564-2010 is still the only dedicated engineering specification

The only dedicated engineering specification for landfill leachate treatment is HJ 564-2010, Leachate treatment project technical specification of municipal solid waste landfill (trial) (approved by the Ministry of Environmental Protection on 2010-02-03, effective 2010-04-01, first issuance). It was developed under the science and standards department of the ministry, applies to leachate treatment projects at municipal solid waste landfills, and serves as the technical basis for environmental impact assessment, engineering consultancy, design and construction, environmental protection acceptance, and subsequent operation and management.

Two caveats matter. The document is a trial text, and the discharge standard referenced in clause 4.1.4 has been revised: GB 16889-2024, Standard for pollution control on the landfill site of municipal solid waste (approved by the Ministry of Ecology and Environment on 2024-07-23, effective 2024-09-01, second revision; GB 16889-2008 repealed on that date) "adjusted the technical requirements for leachate entering centralized wastewater treatment facilities". This is the most important change for leachate projects in recent years and is developed in section 5 below.

2. Design inputs: flow and quality

For flow, clause 5.1.3 gives the empirical formula (leaching coefficient method): Q = I x (C1A1 + C2A2 + C3A3) / 1000, where I is the multi-year average daily rainfall (mm/d) and A1, A2 and A3 are the catchment areas of the active, intermediate-cover and final-cover units. The leaching coefficients are C1 normally 0.5 to 0.8, C2 normally (0.4 to 0.6) C1, and C3 normally 0.1 to 0.2. The clause notes that where data are sufficient I should be taken from 20 years of records, and otherwise from all available years.

For quality, clause 5.2.1 classifies leachate by landfill age into early, mid-late and post-closure. Table 1 gives typical values (mg/L except pH):

• Early leachate: BOD5 4000 to 20000; COD 10000 to 30000; ammonia nitrogen 200 to 2000; SS 500 to 2000; pH 5 to 8.
• Mid-late leachate: BOD5 2000 to 4000; COD 5000 to 10000; ammonia nitrogen 500 to 3000; SS 200 to 1500; pH 6 to 8.
• Post-closure leachate: BOD5 300 to 2000; COD 1000 to 5000; ammonia nitrogen 1000 to 3000; SS 200 to 1000; pH 6 to 9.

The defining feature is that ammonia nitrogen rises with landfill age while biodegradable organic matter falls. Post-closure leachate can carry 1000 to 3000 mg/L of ammonia nitrogen against only 300 to 2000 mg/L of BOD5, a severely unbalanced carbon to nitrogen ratio. That is the fundamental reason aged leachate is far harder to treat than fresh leachate. Clause 5.2.2 adds that water quality should be based on measured data with future trends considered, and Table 1 is only a fallback.

3. Process route: MBR plus NF/RO dominates, but three combinations are allowed

Clause 6.3.1 recommends pretreatment plus biological treatment plus advanced treatment, and also permits pretreatment plus advanced treatment, or biological treatment plus advanced treatment. Clause 6.3.4 states that advanced treatment should be based mainly on nanofiltration and reverse osmosis, targeting suspended solids, dissolved matter and colloids.

Stage parameters follow.

Pretreatment

Clause 6.4.1.1: with hydrolytic acidification as pretreatment, hydraulic retention time should be 2.5 to 5.0 h and pH 6.5 to 7.5. Clause 6.4.1.2: for coagulation, chemical type, dose and dosing method shall be determined from process conditions, test results and chemical quality; common chemicals are aluminium sulfate, polyaluminium chloride, ferrous sulfate, ferric chloride and polyacrylamide (PAM).

Anaerobic

Clause 6.4.2.2: with upflow anaerobic sludge blanket (UASB), the ambient range should be 20 to 30 degrees C and the mesophilic range 30 to 38 degrees C; volumetric COD load should be 5 to 15 kg/(m3.d); pH should be 6.5 to 7.8; biogas utilization or safe combustion facilities shall be provided.

Aerobic and MBR

Clause 6.4.3.2 and Table 2: membrane bioreactors are internal or external. Internal units should use plate microfiltration or ultrafiltration modules or hollow fibre microfiltration or ultrafiltration modules; external units should use tubular ultrafiltration modules. Temperature should be 20 to 35 degrees C and influent COD 1000 to 20000 mg/L. Table 2 parameters:

• Internal: MLSS 8000 to 10000 mg/L; BOD5 sludge load 0.08 to 0.30 kg/(kg.d); nitrate nitrogen sludge load 0.05 to 0.25 kg/(kg.d); excess sludge yield 0.10 to 0.30 kg/kg.
• External: MLSS 10000 to 15000 mg/L; BOD5 sludge load 0.20 to 0.60 kg/(kg.d); nitrate nitrogen sludge load 0.05 to 0.30 kg/(kg.d); excess sludge yield 0.10 to 0.30 kg/kg.

Clause 6.4.3.3 (oxidation ditch): influent COD 2000 to 5000 mg/L; sludge load (BOD5/MLSS) 0.05 to 0.20 kg/kg; MLSS 3000 to 5500 mg/L; sludge age 15 to 30 d; depth 3.50 to 5.00 m. Clause 6.4.3.4 (pure oxygen aeration): oxygen concentration not below 90%; dissolved oxygen 10 to 20 mg/L; MLSS 10000 to 20000 mg/L; influent COD 1000 to 6000 mg/L; HRT 12 to 24 h.

Advanced treatment

Clause 6.4.4.1 (nanofiltration): influent suspended solids should not exceed 100 mg/L and influent conductivity at 20 degrees C should not exceed 40000 uS/cm; temperature 8 to 30 degrees C; pH 5.0 to 7.0; NF flux 15 to 20 L/(m2.h); water recovery not lower than 80%.

Clause 6.4.4.2 (reverse osmosis): influent suspended solids should not exceed 50 mg/L and influent conductivity at 20 degrees C should not exceed 25000 uS/cm; temperature 8 to 30 degrees C; pH 5.0 to 7.0; RO flux 10 to 15 L/(m2.h); water recovery not lower than 70%.

What these floors mean must be worked out explicitly. A series system with 80% NF recovery and 70% RO recovery yields roughly 56% total permeate, so about 44% of the influent volume becomes concentrate. Concentrate is never a negligible by-product.

4. Concentrate: the code gives a direction, not parameters

Clause 6.5.5.2 (under sludge and concentrate treatment) states: concentrate from nanofiltration and reverse osmosis should be treated separately, by incineration, evaporation or other suitable means. This is the entire technical content of HJ 564-2010 on concentrate: a recommendation to treat separately plus three directions, and no design parameters at all. Evaporator type selection, evaporation ratio, ammonia nitrogen level in condensate and co-incineration ratio are all absent.

In practice, recirculation to the landfill has long been used to absorb concentrate, but that route has been narrowed by the new standard. Clause 7.5 of GB 16889-2024: where leachate is disposed of by recirculation, it shall not adversely affect landfill stability; where poor leachate drainage means stability requirements cannot be met, recirculation shall be stopped immediately. Clause 7.6: measures shall be taken to reduce odour during recirculation; surface spraying and other surface recirculation methods shall not be used; where vertical wells or horizontal pipes are used, measures shall prevent odour escape from the wells or pipes.

The practical effect is that recirculation has been downgraded from the default outlet to a strictly constrained one. It also does not solve the pollutant destination: recirculated concentrate continuously accumulates salt and refractory organics. A design document that still treats recirculation as the sole concentrate route needs a dedicated long-term feasibility argument.

On sludge, clause 6.5.5.1: sludge from leachate treatment should be handled together with sludge from municipal wastewater treatment plants; where it is landfilled or treated separately, moisture content should not exceed 80%.

5. The new outlet opened by GB 16889-2024: centralized wastewater treatment

The foreword of GB 16889-2024 states that this revision "adjusted the technical requirements for leachate entering centralized wastewater treatment facilities", and section 9.2 sets out the full provisions:

• Clause 9.2.1: where pollutants are discharged to a centralized wastewater treatment facility, the landfill shall reach agreement with the operator on water quality and quantity, discharge method, monitoring, information sharing, emergency response, breach compensation and dispute resolution, and shall sign a legally binding written contract. Centralized facilities include municipal and industrial wastewater treatment plants.
• Clause 9.2.2: treated leachate shall be discharged uniformly and shall not affect normal operation or treatment performance of the receiving facility.
• Clause 9.2.3: a) leachate shall enter a municipal wastewater treatment plant through a trunk sewer; where it cannot discharge directly to a trunk sewer, a dedicated pipeline to the trunk sewer is required; b) it shall enter an industrial wastewater treatment plant through a dedicated pipeline; c) water pollutants shall meet the limits in Table 4.

The engineering significance is that this provides, for the first time, a standard-backed off-site outlet for leachate itself, not just concentrate, while shifting responsibility onto contract and flow-equalization management. "Uniform discharge" and "no effect on normal operation" are operating criteria, not one-off design criteria, and require equalization and metering facilities.

In addition, clause 10.2.2 requires the landfill to implement online monitoring at the leachate treatment facility discharge outlet, and section 5.3 requires leachate depth above the liner to be not more than 30 cm.

6. Operation and acceptance: mandatory monitoring

Clause 7.1 requires that during commissioning at least the following be monitored: pH, temperature and dissolved oxygen in each unit; influent and effluent SS, COD, BOD5, ammonia nitrogen, total nitrogen and total phosphorus; influent and effluent total mercury, total arsenic, total cadmium, total lead, total chromium, hexavalent chromium and fecal coliform; conductivity or salinity and turbidity of NF and RO influent, permeate and concentrate; and pressure and differential pressure across each membrane module.

Clause 9.1.7: as water quality varies, NF and RO shall take necessary measures such as pH adjustment, antiscalant dosing and proper control of operating parameters to effectively avoid scaling and fouling of membrane modules.

Clause 8.3.3 requires performance tests to report whole-plant techno-economic indicators: total COD removed, power consumption per unit COD removed (kW.h/kg) and operating cost per tonne. These three are the core basis for benchmarking leachate projects.

Clause 4.1.3 is a hard layout requirement: a leachate equalization tank must be provided between the landfill area and the treatment facility. Clause 6.2.3: the equalization tank is one of the plant odour sources and shall be covered and sealed with odour treatment provided. Clause 4.1.5: main equipment shall have standby units and be corrosion resistant.

7. Checklist and the parameters left to testing

1. Base design water quality on measurement; use Table 1 only as a fallback, and check the carbon to nitrogen ratio carefully for aged leachate.
2. Fix the process combination under clause 6.3.1, with advanced treatment based on NF/RO under clause 6.3.4.
3. Back-calculate concentrate volume from the recovery floors in clauses 6.4.4.1 and 6.4.4.2 (80% and 70%) and design it as a standalone unit.
4. Do not rely on recirculation alone for concentrate: clauses 7.5 and 7.6 of GB 16889-2024 constrain it, and the off-site route in section 9.2 should be evaluated in parallel.
5. Provide pH adjustment and antiscalant dosing under clause 9.1.7 and conductivity and differential pressure monitoring under items d) and e) of clause 7.1.
6. Implement online monitoring at the discharge outlet under clause 10.2.2 of GB 16889-2024.

Parameters with no codified value that must be determined by testing include: actual NF/RO recovery (the code gives only floors; the real value is bounded by influent quality and fouling rate), evaporation ratio and condensate ammonia nitrogen for concentrate evaporation, co-incineration ratio, membrane cleaning interval and chemical formulation, and antiscalant dose. HJ 564-2010 gives no values for these and this article offers none.

Process parameters here are taken from Chapters 5, 6, 7 and 8 of HJ 564-2010 (approved 2010-02-03, effective 2010-04-01, trial). Discharge, recirculation and off-site discharge requirements are from GB 16889-2024 (effective 2024-09-01, replacing GB 16889-2008). For the specific values in Table 2 (direct discharge) and Table 4 (indirect discharge) of GB 16889-2024, refer to the official standard text.