A novel sulfate reduction, autotrophic denitrification, nitrification integrated (SANI) process for saline wastewater treatment

This paper reports on a lab-scale evaluation of a novel and integrated biological nitrogen removal process: the sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process that was recently proposed for saline sewage treatment. The process consisted of an up-flow anaerobic sludge bed (UASB) for sulfate reduction, an anoxic filter for autotrophic denitrification and an aerobic filter for nitrification. The experiments were conducted to evaluate the performance of the lab-scale SANI system with synthetic saline wastewater at various hydraulic retention times, nitrate concentrations, dissolved oxygen levels and recirculation ratios for over 500 days. The system successfully demonstrated 95% chemical oxygen demand (COD) and 74% nitrogen removal efficiency without excess sludge withdrawal throughout the 500 days of operation. The organic removal efficiency was dependent on the hydraulic retention time, up-flow velocity, and mixing conditions in the UASB. Maintaining a sufficient mixing condition in the UASB is important for achieving effective sulfate reduction. For a typical Hong Kong wastewater composition 80% of COD can be removed through sulfate reduction. A minimum sulfide sulfur to nitrate nitrogen ratio of 1.6 in the influent of the anoxic filter is necessary for achieving over 90% nitrate removal through autotrophic denitrifiers which forms the major contribution to the total nitrogen removal in the SANI system. Sulfur balance analyses confirmed that accumulation of elementary sulfur and loss of hydrogen sulfide in the system were negligible.     

Simultaneous heterotrophic and sulfur-oxidizing autotrophic denitrification process for drinking water treatment: control of sulfate production

A long-term performance of a packed-bed bioreactor containing sulfur and limestone was evaluated for the denitrification of drinking water. Autotrophic denitrification rate was limited by the slow dissolution rate of sulfur and limestone. Dissolution of limestone for alkalinity supplementation increased hardness due to release of Ca²⁺. Sulfate production is the main disadvantage of the sulfur autotrophic denitrification process. The effluent sulfate concentration was reduced to values below drinking water guidelines by stimulating the simultaneous heterotrophic and autotrophic denitrification with methanol supplementation. Complete removal of 75 mg/L NO₃-N with effluent sulfate concentration of around 225 mg/L was achieved when methanol was supplemented at methanol/NO₃-N ratio of 1.67 (mg/mg), which was much lower than the theoretical value of 2.47 for heterotrophic denitrification. Batch studies showed that sulfur-based autotrophic NO₂-N reduction rate was around three times lower than the reduction rate of NO₃-N, which led to NO₂-N accumulation at high loadings.     

Occurrence of methanogenesis during start-up of a full-scale synthesis gas-fed reactor treating sulfate and metal-rich wastewater

The start-up of a full-scale synthesis gas-fed gas-lift reactor treating metal and sulfate-rich wastewater was investigated. Sludge from a pilot-scale reactor was used to seed the full-scale reactor. The main difference in design between the pilot- and full-scale reactor was that metal precipitation and sulfate reduction occurred in the same reactor. After 7 weeks the full-scale reactor achieved the sulfate conversion design rate of 15 kg/m3day. Zinc sulfide precipitation inside the reactor did not interfere with obtaining a high rate of sulfate reduction. 16S rRNA gene analysis demonstrated that the bacterial communities in both reactors were dominated by the sulfate-reducing genus Desulfomicrobium. Archaeal communities of both reactors were dominated by the methanogenic genus Methanobacterium. Most Probable Number (MPN) counts confirmed that heterotrophic Sulfate-Reducing Bacteria (SRB) were dominant (10(11) -10(12) cells/g VSS) compared to homoacetogens (10(5) -10(6) cells/g VSS) and methanogens (10(8) -10(9) cells/g VSS). Methanogenesis was not suppressed during start-up of the full scale-reactor, despite the predominance of SRB, which have a lower hydrogen threshold. Due to the short sludge retention time (4-7 days) competition for hydrogen is determined by Monod kinetics, not hydrogen thresholds. As the kinetic parameters for SRB and methanogens are similar, methanogenesis may persist which results in a loss of hydrogen.     

Effect of COD/SO(4)(2-) ratio and sulfide on thermophilic (55 degrees C) sulfate reduction during the acidification of sucrose at pH 6

This study investigated the effect of the COD/SO₄²⁻ ratio (4 and 1) and the sulfide concentration on the performance of thermophilic (55 °C) acidifying (pH 6) upflow anaerobic sludge bed reactors fed with sucrose at an organic loading rate of 4.5 g COD l_reactor⁻¹ day⁻¹. Sulfate reduction efficiencies amounted to 65% and 25-35% for the COD/SO₄²⁻ ratios of 4 and 1, respectively. Acidification was complete at all the tested conditions and the electron flow was similar at the two COD/SO₄²⁻ ratios applied. The stepwise decrease of the sulfide concentrations in the reactors with a COD/SO₄²⁻ ratio of 1 by N₂ stripping caused an immediate stepwise increase in the sulfate reduction efficiencies, indicating a reversible inhibition by sulfide. The degree of reversibility was, however, affected by the growth conditions of the sludge. Acidifying sludge pre-grown at pH 6, at a COD/SO₄²⁻ ratio of 9 and exposed for 150 days to 115 mg l⁻¹ sulfide, showed a slower recovery from the sulfide inhibition than a freshly harvested sludge from a full scale treatment plant (pH 7 and COD/SO₄²⁻=9.5) exposed for a 70 days to 200 mg l⁻¹ sulfide. In the latter case, the decrease of the sulfide concentration from 200 to 45 mg l⁻¹ (35 mg l⁻¹ undissociated sulfide) by N₂ stripping caused an immediate increase of the sulfate reduction efficiency from 35% to 96%.     

Advanced treatment of sewage by pre-coagulation and biological filtration process

A pre-coagulation and bio-filtration process for advanced treatment of sewage was developed and experimentally discussed with a pilot plant. The bio-filtration unit consists of a denitrification filter, a nitrification filter with side stream to the denitrification filter, and a polishing filter with anoxic and aerobic parts. Concentrations of SS, T-COD(Cr), T-carbonaceous BOD, T-N and T-P in the effluent were stably kept at less than 3, 20, 5mg/L, 2mg N/L and 0.2mg P/L, respectively, and transparency at higher than 100 cm, under total hydraulic retention time of 3.2h in the bio-filtration parts (filter-bed). ORP in an anoxic tank before a nitrification tank should be at a low level of less than -120 mV to keep remaining NO(-)(x) - N less than 1mg N/L, but must be maintained at a level higher than -150 mV. The maximum nitrogen-loading rate under a water temperature of 18 degrees C should be less than 0.25 kg N/(m(3)-filter-bed.d). Concentrations of microorganisms kept in the reactors were as high as 4000-5000 mg COD/L-filter-bed. Denitrification activity of 0.4 or 0.7 kg N/(m(3)-filter-bed.d), and nitrification activity of 0.3 kg N/(m(3)-filter-bed.d) were obtained, respectively, under a water temperature of about 18 degrees C. Backwashing in each tank as well as methanol addition and aeration in the polishing filter were operated successfully by the automatic control systems. These results proved that this process is applicable to advanced treatment of sewage with easy maintenance.     

Possible cause of excess sludge reduction in an oxic-settling-anaerobic activated sludge process (OSA process)

Modification of a conventional activated sludge process by inserting a sludge holding tank in a sludge return line forms an oxic-settling-anaerobic (OSA) process that may provide a cost-effective way to reduce excess sludge production in activated sludge processes. In this paper we systematically evaluate the following possible scenarios that may explain the reduction of excess sludge in the OSA process: (i). energy uncoupling, (ii). domination of slow growers, (iii). soluble microbial products (SMPs) effect and (iv). sludge decay in the sludge holding tank under a low oxidation-reduction potential (ORP) condition. Results show that only the final scenario may reasonably explain this reduction. It has also been found that the sludge decay process in the sludge holding tank may involve the reduction of the cell mass.     

Simultaneous nitrification and denitrification in a CEM (cation exchange membrane)-bounded two chamber system

A novel process was developed to induce a simultaneous oxidation of ammonia and denitrification in a single system consisting of two chambers separated by a cation exchange membrane. One was an anoxic chamber and the other was an aerobic chamber. The maximum mass flux via the membrane was calculated as 0.83 mg NH₄⁺-N/m² s in a batch test when the initial concentration of NH₄⁺ was 700 mg N/L. And it was observed that NO₃⁻ and NO₂⁻ moved via the membrane in a reverse direction when NH₄⁺ was transported. When the system was operated in a continuous mode by feeding a wastewater containing glucose and NH₄⁺, it was observed that soluble chemical oxygen demand and NH₄⁺ were simultaneously removed showing 99% and 71  86% of efficiency, respectively. Denitrification occurred in the anoxic chamber and nitrification was carried out in the aerobic chamber.     

Effects of carbon source on denitrification efficiency and microbial community structure in a saline wastewater treatment process

Two different denitrifying reactors were monitored in order to evaluate the effects of carbon source on denitrification efficiency and microbial community structure under various saline conditions. Nitrogen removal performances were determined when salinity concentrations increase gradually in acetate- or methanol-fed denitrifying reactor. As a result, acetate-fed process attained high nitrate removal at 0-10% NaCl, while methanol was proven beneficial electron donors at 0-3% NaCl. A parallel analysis of T-RFLP and cloning in the acetate-fed sludge showed that a specialized microbial population (i.e. the genera Halomonas and Marinobacter) adapted to a high saline environment. Meanwhile, there were no major changes of bacterial populations in the methanol-fed reactor at 4% NaCl, although the relative abundances of the genera Azoarcus and Methylophaga increased when salinity concentration was at 1-3% NaCl, indicating that methanol-utilizing populations in activated sludge was unable to adapt to a high saline environments (>4% NaCl).     

Effect of specific gas loading rate on thermophilic (55 degrees C) acidifying (pH 6) and sulfate reducing granular sludge reactors

The effect of the specific gas loading rate on the acidifying, sulfate reducing and sulfur removal capacity of thermophilic (55 degrees C; pH 6.0) granular sludge bed reactors treating partly acidified wastewater was investigated. A comparison was made between a regular UASB reactor and a UASB reactor continuously sparged with N(2) at a specific gas loading rate of 30 m(3)m(-2)d(-1). Both UASB reactors (upflow velocity 1.0 mh(-1), hydraulic retention time about 5h) were fed a synthetic wastewater containing starch, sucrose, lactate, propionate and acetate and a low sulfate concentration (COD/SO(4)(2-) ratio of 10) at volumetric organic loading rates (OLR) ranging from 4.0 to 49.8 gCODl(-1) reactord(-1). Immediately after imposing an OLR of 25 gCODl(-1) reactord(-1), the acidification and sulfate reduction efficiency dropped to 80% and 30%, respectively, in the UASB reactor. Both efficiencies recovered slowly to 100% during the course of the experiment. In the N(2) sparged reactor, both the acidification and sulfate reduction efficiency remained 100% following the OLR increase to 25 gCODl(-1) reactord(-1). However, the sulfate reduction efficiency gradually decreased to about 20% at the end of the experiment. The biogas (CO(2) and CH(4)) production rate in the UASB was very low, i.e. <3l biogasl(-1) reactorday(-1), resulting in negligible amounts (<20%) of H(2)S stripped from the reactor liquid. The total H(2)S concentration of the N(2) sparged UASB reactor effluent was always below 25 mgl(-1), but incomplete sulfate reduction kept the maximal H(2)S stripping efficiency below 70%.     

有机负荷对污泥减量HA-A/A-MCO工艺吸放磷的影响

开发了一种具有同步除磷脱氮和污泥减量功能的HA-A/A-MCO工艺,分析了该工艺的方法及流程,并对其进行了试验研究,通过静态试验发现,当负荷增加至一定程度,有机物不再是磷释放的限制性因子,HA-A/A-MCO系统厌氧释磷的临界有机负荷为0.141 g COD/（g MLSS.d）,单位污泥最大可释放贮磷量为5.7 mg P/g MLSS。     

Impact of process design on greenhouse gas (GHG) generation by wastewater treatment plants

The overall on-site and off-site greenhouse gas emissions by wastewater treatment plants (WWTPs) of food processing industry were estimated by using an elaborate mathematical model. Three different types of treatment processes including aerobic, anaerobic and hybrid anaerobic/aerobic processes were examined in this study. The overall on-site emissions were 1952, 1992, and 2435 kg CO₂e/d while the off-site emissions were 1313, 4631, and 5205 kg CO₂e/d for the aerobic, anaerobic and hybrid treatment systems, respectively, when treating a wastewater at 2000 kg BOD/d. The on-site biological processes made the highest contribution to GHG emissions in the aerobic treatment system while the highest emissions in anaerobic and hybrid treatment systems were obtained by off-site GHG emissions, mainly due to on-site material usage. Biogas recovery and reuse as fuel cover the total energy needs of the treatment plants for aeration, heating and electricity for all three types of operations, and considerably reduce GHG emissions by 512, 673, and 988 kg CO₂e/d from a total of 3265, 6625, and 7640 kg CO₂e/d for aerobic, anaerobic, and hybrid treatment systems, respectively. Considering the off-site GHG emissions, aerobic treatment is the least GHG producing type of treatment contrary to what has been reported in the literature.     

Removal of arsenic from water: Effects of competing anions on As(III) removal in KMnO4–Fe(II) process

Effects of sulfate, phosphate, silicate and humic acid (HA) on the removal of As(III) in the KMnO₄–Fe(II) process were investigated in the pH range of 4–9 with permanganate and ferrous sulfate applied at selected dosage. Sulfate decreased the removal of arsenic by 6.5–36.0% at pH 6–9 and the decrease in adsorption did not increase with increasing concentration of sulfate from 50 to 100 mg/L. In the presence of 1 mg/L phosphate, arsenic removal decreased gradually as pH increased from 4 to 6, and a sharp drop occurred at pH 7–9. The presence of 10 mg/L silicate had negligible effect on arsenic removal at pH 4–5 whereas decreased the arsenic removal at pH 6–9 and the decrease was more significant at higher pH. The presence of HA dramatically decreased the arsenic removal over the pH range of 6–9 and HA of higher concentration resulted in greater drop in arsenic removal. The effects of the competing anions on arsenic removal in the KMnO₄–Fe(II) process were highly dependent on pH and the degree of these four anions influencing As(III) removal decreased in the following order, phosphate > humic acid > silicate > sulfate. Sulfate differed from the other three anions because sulfate decreased the removal of arsenic mainly by competitive adsorption while phosphate, silicate and HA decreased the removal of As(III) by competitive adsorption and sequestering the formation of ferric hydroxide derived from Fe(II).     

Evaluation of wastewater nitrogen transformation in a natural wetland (Ulaanbaatar, Mongolia) using dual-isotope analysis of nitrate

The Tuul River, which provides water for the daily needs of many residents of Ulaanbaatar, Mongolia, has been increasingly polluted by wastewater from the city's sewage treatment plant. Information on water movement and the transformation of water-borne materials is required to alleviate the deterioration of water quality. We conducted a synoptic survey of general water movement, water quality including inorganic nitrogen concentrations, and isotopic composition of nitrogen (δ¹⁵N-NO₃⁻, δ¹⁸O-NO₃⁻, and δ¹⁵N-NH₄⁺) and water (δ¹⁸O-H₂O) in a wetland area that receives wastewater before it enters the Tuul River. We sampled surface water, groundwater, and spring water along the two major water routes in the wetland that flow from the drain of the sewage treatment plant to the Tuul River: a continuous tributary and a discontinuous tributary. The continuous tributary had high ammonium (NH₄⁺) concentrations and nearly stable δ¹⁵N-NH₄⁺, δ¹⁵N-NO₃⁻, and δ¹⁸O-NO₃⁻ concentrations throughout its length, indicating that nitrogen transformation (i.e., nitrification and denitrification) during transit was small. In contrast, NH₄⁺ concentrations decreased along the discontinuous tributary and nitrate (NO₃⁻) concentrations were low at many points. Values of δ¹⁵N-NH₄⁺, δ¹⁵N-NO₃⁻, and δ¹⁸O-NO₃⁻ increased with flow along the discontinuous route. Our results indicate that nitrification and denitrification contribute to nitrogen removal in the wetland area along the discontinuous tributary with slow water transport. Differences in hydrological pathways and the velocity of wastewater transport through the wetland area greatly affect the extent of nitrogen removal.     

Dynamics of phosphorus, nitrogen and carbon removal in a horizontal subsurface flow constructed wetland

The dynamics of nitrogen (N), phosphorus (P) and carbon (C) accumulation in the filter material of a horizontal subsurface constructed wetland (HSSF CW; established in 1997) and in a specially designed oil-shale ash filter (2002) for P retention have been studied. Concentrations of N, P and C in filter media (coarse sand) in the HSSF beds show an increasing trend. Both the annual accumulation of P and increasing outflow concentrations of P in the HSSF CW reflect the possible saturation of filter media with P after 8 years working. Tested ash material derived from oil-shale combustion demonstrated very high P removal efficiency in laboratory batch experiments. However, during the first 4 months of the in situ ash filter experiment, the efficiency of P removal was about 71% (an average outflow concentration of 1.9 mg L(-1) was achieved). Subsequently, the efficiency decreased to 10-20%, which might be a sign of saturation or clogging due to quick biofilm development on the ash particles. The increasing of hydraulic retention time and the improvement of design for maximal contact between material and wastewater are considered to be key factors that can provide optimal pH for the removal processes.     

Saline sewage treatment using a submerged anaerobic membrane reactor (SAMBR): Effects of activated carbon addition and biogas-sparging time

This study investigated the performance of a submerged anaerobic membrane reactor (SAMBR) treating saline sewage under fluctuating concentrations of salinity (0-35 g NaCl/L), at 8 and 20 h HRT, with fluxes ranging from 5-8 litres per square metre per hour (LMH). The SAMBRs attained a 99% removal of Dissolved Organic Carbon (DOC) with 35 g NaCl/L, while removal inside the reactor was significantly lower (40-60% DOC). Even with a sudden drop in salinity overall removal recovered quickly, while the recovery inside the reactor took place at a slower rate. This highlights the positive effect of the membrane in preventing the presence of high molecular weight organics in the effluent while also retaining biomass inside the reactor so that they can rapidly acclimatize to salinity. The reduction of continuous biogas sparging to intervals of 10 min ON and 5 min OFF resulted in a slight increase in transmembrane pressure (TMP) by 0.025 bar, but also resulted in an increase in effluent DOC removal and inside the SAMBR by 10% and 20%, respectively. The addition of powdered activated carbon (PAC) resulted in a decrease in the TMP by 0.070 bar, and an increase in DOC removal in the reactor and effluent by 30% and 5%, respectively. The PAC dramatically decreased the high molecular weight organics in the reactor over a period of 72 h. SEM pictures of the membrane and biomass before and after addition of PAC revealed a remarkable reduction of flocks on the membrane surface, and a reduction inside the reactor of soluble microbial products (SMPs). Finally, Energy Dispersive X-ray (EDX) analysis of the membranes pores and biofilm highlighted the absence of organic matter in the inner pores of the membrane.     

Effects of chloride,sulfate and natural organic matter (NOM) on the accumulation and release of trace-level inorganic contaminants from corroding iron

This study examined effects of varying levels of anions (chloride and sulfate) and natural organic matter (NOM) on iron release from and accumulation of inorganic contaminants in corrosion scales formed on iron coupons exposed to drinking water. Changes of concentrations of sulfate and chloride were observed to affect iron release and, in lesser extent, the retention of representative inorganic contaminants (vanadium, chromium, nickel, copper, zinc, arsenic, cadmium, lead and uranium); but, effects of NOM were more pronounced. DOC concentration of 1 mg/L caused iron release to increase, with average soluble and total iron concentrations being four and two times, respectively, higher than those in the absence of NOM. In the presence of NOM, the retention of inorganic contaminants by corrosion scales was reduced. This was especially prominent for lead, vanadium, chromium and copper whose retention by the scales decreased from >80% in the absence of NOM to <30% in its presence. Some of the contaminants, notably copper, chromium, zinc and nickel retained on the surface of iron coupons in the presence of DOC largely retained their mobility and were released readily when ambient water chemistry changed. Vanadium, arsenic, cadmium, lead and uranium retained by the scales were largely unsusceptible to changes of NOM and chloride levels. Modeling indicated that the observed effects were associated with the formation of metal–NOM complexes and effects of NOM on the sorption of the inorganic contaminants on solid phases that are typical for iron corrosion in drinking water.     

CAST、UNITANK、氧化沟的生物除磷工艺设计和运行

对CAST、UNITANK和氧化沟三种二级强化生物除磷工艺的不同设计形式进行了分析,结合污水处理厂的实际运行情况,总结了设计的优缺点,同时指出了强化生物除磷工艺运营管理的控制措施。     

Biological and chemical interactions with U(VI) during anaerobic enrichment in the presence of iron oxide coated quartz

Microcosm experiments were performed to understand chemical and biological interactions with hexavalent uranium (U(VI)) in the presence of iron oxide bearing minerals and trichloroethylene (TCE) as a co-contaminant. Interactions of U(VI) and hydrous iron oxide moieties on the mineral oxide surfaces were studied during enrichments for dissimilatory iron reducing (DIRB) and sulfate reducing bacteria (SRB). Microbes enriched from groundwater taken from the Test Area North (TAN) site at the Idaho National Laboratory (INL) were able to reduce the U(VI) in the adsorption medium as well as the iron on quartz surfaces. Early in the experiment disappearance of U(VI) from solution was a function of chemical interactions since no microbial activity was evident. Abiotic removal of U(VI) was enhanced in the presence of carbonate. As the experiment proceeded, further removal of U(VI) from solution was associated with the fermentation of lactate to propionate and acetate. During later phases of the experiment when lactate was depleted from the growth medium in the microcosm containing the DIRB enrichments, U(VI) concentrations in the solution phase increased until additional lactate was added. When additional lactate was added and fermentation proceeded, U(VI) concentrations in the liquid phase again returned to near zero. Similar results were shown for the SRB enrichment but lower uranium concentrations were seen in the liquid phase, while in the enrichment with carbonate a similar increase in uranium concentration was not seen. Chemical and biological interactions appear to be important on the mobilization/immobilization of U(VI) in an iron oxide system when TCE is present as a co-contaminant. Interestingly, TCE present in the microcosm experiments was not dechlorinated which was probably an effect of redox conditions that were unsuitable for reductive dechlorination by the microbial culture tested.     

The effect of anoxia and anaerobia on ciliate community in biological nutrient removal systems using laboratory-scale sequencing batch reactors (SBRs)

Little is known about the effect of anaerobic and anoxic stages on the protozoan community in the activated sludge process and how this subsequently affects performance. Using a laboratory-scale BNR system the effect of different periods of anoxia on both the protozoan community and performance efficiency have been examined. Four SBRs were operated at two cycles per day using a range of combined anoxic/anaerobic periods (0, 60, 120 and 200 min). Effluent quality (TOC, BOD, TP, TN, NH₄-N, NO₃-N and NO₂-N), sludge settleability and ciliate community (species diversity and abundance) were analysed over a periods of up to 24 days of operation. The species richness and total abundance of ciliates were found to decrease with longer anoxic/anaerobic periods. Both, positive and negative significant correlations between the abundance of certain species and the period of anoxia was observed (e.g. Opercularia microdiscum, Epicarchesium granulatum), although other species (i.e. Acineria uncinata, Epistylis sp.) were unaffected by exposure to anoxia. In the laboratory-scale units, the 60 min anoxic/anaerobic period resulted in good process performance (TOC and BOD removal of 97-98% respectively), nitrification (80-90%), denitrification (52%) but poor levels of biological P-removal (12%); with the protozoan community moderately affected but still diverse with high abundances. Increasing the length of anoxia to up to 200 min did not enhance denitrification although P-removal rates increased to between 22 and 33%; however, ciliate species richness and total abundance both decreased and sludge settleability became poorer. The study shows that activated sludge ciliate protozoa display a range of tolerances to anoxia that result in altered ciliate communities depending on the length of combined anoxic/anaerobic periods within the treatment process. It is recommended that anoxic/anaerobic periods should be optimised to sustain the protozoan community while achieving maximum performance and nutrient removal.     

Removal of refractory compounds from stabilized landfill leachate using an integrated H2O2 oxidation and granular activated carbon (GAC) adsorption treatment

This study investigated the treatment performances of H₂O₂ oxidation alone and its combination with granular activated carbon (GAC) adsorption for raw leachate from the NENT landfill (Hong Kong) with a very low biodegradability ratio (BOD₅/COD) of 0.08. The COD removal of refractory compounds (as indicated by COD values) by the integrated H₂O₂ and GAC treatment was evaluated, optimized and compared to that by H₂O₂ treatment alone with respect to dose, contact time, pH, and biodegradability ratio. At an initial COD concentration of 8000 mg/L and NH₃-N of 2595 mg/L, the integrated treatment has substantially achieved a higher removal (COD: 82%; NH₃-N: 59%) than the H₂O₂ oxidation alone (COD: 33%; NH₃-N: 4.9%) and GAC adsorption alone (COD: 58%) at optimized experimental conditions (p ≤ 0.05; t-test). The addition of an Fe(II) dose at 1.8 g/L further improved the removal of refractory compounds by the integrated treatment from 82% to 89%. Although the integrated H₂O₂ oxidation and GAC adsorption could treat leachate of varying strengths, treated effluents were unable to meet the local COD limit of less than 200 mg/L and the NH₃-N of lower than 5 mg/L. However, the integrated treatment significantly improved the biodegradability ratio of the treated leachate by 350% from 0.08 to 0.36, enabling the application of subsequent biological treatments for complementing the degradation of target compounds in the leachate prior to their discharge.