厌氧序批式活性污泥工艺(ASBR)特性研究

通过正交试验,探讨了ＡＳＢＲ工艺最为重要的两个操作参数即充水时间和负荷率对ＡＳＢＲ工艺过程的影响。试验表明,充水时间和负荷率明显影响着ＡＳＢＲ的工艺过程,如出水水质、循环周期等。而且,充水时间和负荷率相互之间也存在着制约关系。     

Psychrophilic and mesophilic anaerobic digestion of brewery effluent: a comparative study

Two expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactors (3.38 l active volume) were used to directly compare psychrophilic (15 degrees C), anaerobic digestion (PAD) to mesophilic (37 degrees C) anaerobic digestion (MAD) for the treatment of a brewery wastewater (chemical oxygen demand (COD) concentration of 3,136+/-891 mg l(-1)). Bioreactor performance was evaluated by COD removal efficiency and biogas yields at a range of hydraulic and organic loading rates. Specific methanogenic activity (SMA) assays were also employed to investigate the activity of the biomass in the bioreactors. No significant difference in the COD removal efficiencies (which ranged from 85-93%) were recorded between PAD and MAD during the 194-d trial at maximum organic and hydraulic loading rates of 4.47 kg m(-3) day(-1) and 1.33 m(3) m(-3) day(-1), respectively. In addition, the methane content (%) of the biogas was very similar. The volumetric biogas yield from the PAD bioreactor was approximately 50% of that from the MAD bioreactor at an organic loading rate of 4.47 kg COD m(-3) day(-3) and an applied liquid up-flow velocity (V(up)) of 2.5 m h(-1). Increasing the V(up) in the PAD bioreactor to 5 m h(-1) resulted in a volumetric biogas production rate of approximately 4.1 l d(-1) and a methane yield of 0.28 l CH(4) g(-1) COD d(-1), which were very similar to the MAD bioreactor. Significant and negligible biomass washout was observed in the mesophilic and psychrophilic systems, respectively, thus increasing the sludge loading rate applied to the former and underlining the robustness of the latter, which appeared underloaded. A psychrotolerant mesophilic, but not truly psychrophilic, biomass developed in the PAD bioreactor biomass, with comparable maximum SMA values to the MAD bioreactor biomass. PAD, therefore, was shown to be favourably comparable to MAD for brewery wastewater treatment and biogas generation.     

Halophilic biological treatment of tannery soak liquor in a sequencing batch reactor

Hypersaline wastewater (i.e. wastewater containing more than 35 gl(-1) total dissolved solids (TDS)) is generated by various industrial activities. This wastewater, rich in both organic matter and TDS, is difficult to treat using conventional biological wastewater treatment processes. Among the industries generating hypersaline effluents, tanneries are prominent in India. In this study, tannery wastewater from soak pit was treated in a lab-scale SBR for the removal of organic matter. The characterisation of the soak liquor showed that this effluent is biodegradable, though not easily, and highly variable, depending on the origin and the nature of the hides. TDS was in the range of 21-57 gl(-1) and COD was in the range of 1.5-3.6 gl(-1). This soak liquor was biologically treated in an aerobic sequencing batch reactor seeded with halophilic bacteria, and the performance of the system was evaluated under different operating conditions with changes in hydraulic retention time, organic loading rate and salt concentration. The changes in salinity appeared to affect the removal of organic matter more than the changes in hydraulic retention time or organic loading rate. Despite the variations in the characteristics of the soak liquor, the reactor achieved proper removal of organic matter, once the acclimation of the microorganisms was achieved. Optimum removal efficiencies of 95%, 93%, 96% and 92% on COD, PO4 3-, TKN and SS, respectively, could be reached with 5 days hydraulic retention time (HRT), an organic loading rate (OLR) of 0.6 kg COD m(-3)d(-1) and 34 g NaCl l(-1). The organisms responsible for nitrogen removal appeared to be the most sensitive to the modifications of these parameters.     

Anaerobic pre-treatment of herbal-based pharmaceutical wastewater using fixed-film reactor with recourse to energy recovery

The concept of immobilization technology has been incorporated in this research study for biomethanation of high strength herbal based pharmaceutical wastewater. Accordingly, an investigation has been made on laboratory scale to assess the feasibility of an anaerobic fixed film fixed bed reactor system to pre-treat herbal-based pharmaceutical wastewater with recourse to energy recovery, including influence of operating conditions. The work was carried out with laboratory-scale upflow reactor, equipped with nylon scrubber as random support. The reactor was operated at 35 degrees C. COD removal efficiencies ranging from 76 to 98% were achieved for organic loading rates upto 10 kgCOD/m3 d, while the highest organic loading rate (around 48 kg COD/m3 d) led to efficiencies of 46-50%. The influences of hydraulic retention time and substrate concentration were also studied. The reactors did now show destabilization under impulse hydraulic and organic overloadings. Reactor stability was easily achieved under intermittent operation, with breaks, after which the reactors rapidly returned to their optimal performance.     

Characteristics of sludge developed under different loading conditions during UASB reactor start-up and granulation

Sludge characteristics available inside the reactor are of vital importance to maximize advantages of UASB reactor. The organic loading rate and sludge loading rate applied during start-up are among the important parameters to govern the sludge characteristics. Effects of these loading rates on the characteristics of the sludge developed are evaluated in six laboratory scale UASB reactors. The sludge characteristics considered are VSS/SS ratio of the sludge, sludge volume index, specific gravity, settling velocity and metal contents of the sludge developed under different loading rates. The experimental results indicate that, for developing good characteristics sludge, during primary start-up from flocculent inoculum sludge, organic loading rate and sludge loading rate should be in the range of 2.0-4.5 kg COD/m3 d and 0.1-0.25 kg COD/kg VSS d, respectively (chemical oxygen demand, COD). Proper sludge granulation and higher COD removal efficiency will be achieved by these loading rates.     

Treatment of anaerobically pre-treated domestic sewage by a rotating biological contactor.

The performance of a rotating biological contactor (RBC) for the post-treatment of the effluent of an up-flow anaerobic sludge blanket (UASB) was the subject of this study. Different hydraulic and organic loading rates have been investigated. The removal efficiencies of COD(total), COD(suspended), COD(colloidal) and COD(soluble) increased at a higher hydraulic retention time (HRT) and a lower influent organic loading rate. The results obtained indicated that a two-stage RBC reactor at an HRT of 10 h and an organic loading rate of 6.4g COD m(-2) d(-1) represents an effective post-treatment process. Most COD(suspended) and COD(colloidal) were removed in the first stage while nitrification proceeded in the second stage. The overall nitrification efficiency was 92% at an ammonia loading rate of 1.1 gm(-2) d(-1). Total E. coli removal at HRTs of 10, 5 and 2.5h were 99.5%, 99.0% and 89.0%. respectively. The major part of suspended E. coli ( >4.4 microm) was removed by sedimentation or by adsorption in the biofilm of the first stage of RBC (99.66%). However, E. coli in the colloidal fraction (<4.4 to >0.45 microm) was eliminated in the second stage of RBC (99.78%). A comparison of the performance of a one-stage versus two-stage RBC system, operated at the same total loading rate, revealed an improvement in the effluent quality of the two-stage effluent as compared to the one-stage effluent. The two stages RBC were used to examine the effect of hydraulic shock loads on reactor performance in terms of COD, nitrification and E. coli removal.     

Development of anaerobic migrating blanket reactor (AMBR), a novel anaerobic treatment system

A novel anaerobic treatment system, the anaerobic migrating blanket reactor (AMBR), was developed after completing a parallel study with upflow anaerobic sludge blanket (UASB) and anaerobic sequencing batch reactor (ASBR) processes. Using sucrose as the main component of a synthetic wastewater, the AMBR achieved a maximum chemical oxygen demand (COD) loading rate of 30 g.l-1.day-1 at a 12-h hydraulic retention time (HRT). This resulted in a standard methane production rate (SMPR) of 6.51.l-1.day-1 and an average methane-based COD (MCOD) removal efficiency of 62.2%. A key element in granular biomass formation was migration of the biomass blanket through the reactor. Although a carbohydrate-rich wastewater was used, no separate pre-acidification was required for the AMBR, because of high mixing intensities and wash out of acidogenic bacteria. In contrast, the absence of pre-acidification created "bulking" problems (caused by abundant acidogenic bacteria at the surface of granules) in a UASB reactor, operated under conditions similar to that of the AMBR. As a result, a maximum COD loading rate and SMPR of 21 g.l-1.day-1 and 4.91.l-1.day-1 were achieved, respectively, for the UASB reactor at a 12-h HRT. These values were 18 g.l-1.day-1 and 3.71.l-1.day-1, respectively, for an ASBR at a 12-h HRT. Hence, the performance of the AMBR in treating a carbohydrate-rich wastewater was found to be superior in terms of maximum loading rate and SMPR.     

Pre-acidification in anaerobic sludge bed process treating brewery wastewater

The effect of pre-acidification on anaerobic granule bed processes treating brewery wastewater was the focus of a comparison study employing two configurations, (a) a single stage upflow anaerobic sludge bed (UASB) and (b) an upflow acidification reactor in series with a methanogenic UASB. The pre-acidification reactor achieved 20±4% SCOD removal and 0.08±0.003 L of methane produced per gram of SCOD removal at a hydraulic retention time (HRT) of 0.75–4 h. Butyric acid was not detected and short chain fatty acids (SCFAs) were mainly acetic and propionic acids. The acidification ratio was about 0.42±0.02 g SCFAs as COD/g of influent COD.

Both systems’ critical loading rate to achieve 80% COD removal was established at 34–39 kg COD/m³ of total sludge bed volume per day. SCOD removal efficiency of 90±3% was achieved by both systems at an organic loading rate of 25±1 kg COD/m³ of total sludge bed volume per day, indicating that the installation of an acidification reactor had no effect in terms of the maximum granular activity, biomass granulation and the settleability of granules. At an organic loading rate of 67 kg COD/m³ of total sludge bed volume per day at an HRT of 1 h, the series system outperformed the single UASB by a removal of 62 compared to 57%.     

Carbohydrate storage in anaerobic sequencing batch reactors

This study demonstrates the accumulation and degradation of trehalose as a storage compound in a glucose-fed anaerobic sequencing batch reactor (ASBR). One hour after substrate addition, only 40% of the added organic matter (as chemical oxygen demand, COD) was accounted for by the cumulative methane production and soluble COD remaining in the reactor. All influent COD was accounted for by methane and biomass production by the end of the 24-h ASBR cycle. These dynamics can be explained by the production of an intracellular storage product. Total carbohydrate analysis showed that 26% of the glucose added to the reactor transiently accumulated within the biomass. Based on ¹³C-nuclear magnetic resonance (NMR) analysis, trehalose (-d-glucopyranosyl-(d-glucopyranoside)) was identified as the main carbohydrate produced. Mathematical modeling was performed and the IWA Anaerobic Digestion Model No. 1 (ADM1) was modified to include microbial storage. The modified model adequately described the ASBR dynamics during a 24-h cycle.     

Simultaneous organic and nitrogen removal from municipal landfill leachate using an anaerobic-aerobic system

An anaerobic-aerobic system including simultaneous methanogenesis and denitrification was introduced to treat organic and nitrogen compounds in immature leachate from a landfill site. Denitrification and methanogenesis were successfully carried out in the anaerobic reactor while the organic removal and nitrification of NH4+,-N were carried out in the aerobic reactor when rich organic substrate was supplied with appropriate hydraulic retention time. The maximum organic removal rate was 15.2 kg COD/m3 d in the anaerobic reactor while the maximum NH4+-N removal rate and maximum nitrification rate were 0.84kg NH4+-N/m3/d and 0.50kg NO3--N/m3/d, respectively, in the aerobic reactor. The pH range for proper nitrification was 6-8.8 in the aerobic reactor. The organic compounds inhibited nitrification so that the organic removal in the anaerobic reactor could enhance the nitrification rate in the following aerobic reactor. The gas production rate was 0.33 m3/kg COD and the biogas compositions of CH4, CO2, and N2 were kept relatively constant, 66-75, 22-32, and 2-3%, respectively.     

Performance of an up-flow anaerobic stage reactor (UASR) in the treatment of pharmaceutical wastewater containing macrolide antibiotics

The performance of an up-flow anaerobic stage reactor (UASR) treating pharmaceutical wastewater containing macrolide antibiotics was investigated. Specifically, it was determined whether a UASR could be used as pre-treatment system at an existing pharmaceutical production plant to reduce the antibiotics in the trade effluent. Accordingly, a UASR was developed with an active reactor volume of 11 L being divided into four 2.75 L stages. Each stage of the reactor was an up-flow sludge blanket reactor and had a 3-phase separator baffle to retain biomass. The reactor was fed with real pharmaceutical wastewater containing Tylosin and Avilamycin antibiotics and operated with step-wise increases in the reactor organic loading rate (OLR) from 0.43 to 3.73 kg chemical oxygen demand (COD) m(-3)d(-1), and then reduced to 1.86, over 279 days. The process performance of the reactor was characterised in terms of its COD removal, Tylosin reduction, pH, VFA production, methane yield and sludge washout. At a total hydraulic retention time (HRT) of 4 d and OLR of 1.86 kg COD m(-3)d(-1), COD reduction was 70-75%, suggesting the biomass had acclimated to the antibiotics. Furthermore, an average of 95% Tylosin reduction was achieved in the UASR, indicating that this antibiotic could be degraded efficiently in the anaerobic reactor system. In addition, the influence of elevated Tylosin concentrations on the UASR process performance was studied using additions of Tylosin phosphate concentrate. Results showed similar efficiency for COD removal when Tylosin was present at concentrations ranging from 0 to 400 mgL(-1) (mean removal over this range was 93%), however, at Tylosin concentrations of 600 and 800 mgL(-1) there was a slight decline in treatment efficiency at 85% and 75% removal, respectively.     

聚季胺盐投加方式对厌氧污泥颗粒化的影响研究

投加阳离子聚合物是加速厌氧污泥颗粒化的有效方法,根据静态试验得出的聚季胺盐投加总量,选定了聚季胺盐的几种投加方式（不同的投加量和投加时间间隔）,研究其对实验室规模下的厌氧序批式反应器（ASBR）中污泥颗粒化的影响.试验以污水厂的厌氧污泥为对象,以污泥颗粒的粒径、沉速及出水COD等作为评价污泥颗粒化进程的指标,分析了各投加方式对污泥颗粒化进程的影响,并挑选出适宜的絮凝剂投加方式.结果表明,不同投加方式对ASBR污泥颗粒化进程有不同影响,建议采用每次投加量为0.16～0.32 mg/gMLSS,投加时间间隔为2～5 d,分5～10次投加的方式.     

Influence of the agitation rate on the treatment of partially soluble wastewater in anaerobic sequencing batch biofilm reactor

This work reports on the influence of the agitation rate on the organic matter degradation in an anaerobic sequencing batch reactor, containing biomass immobilized on 3 cm cubic polyurethane matrices, stirred mechanically and fed with partially soluble soymilk substrate with mean chemical oxygen demand (COD) of 974+/-70 mg l(-1). Hydrodynamic studies informed on the homogenization time under agitagion rates from 500 to 1100 rpm provided by three propeller impellers. It occurred very quickly compared to the total cycle time. The results showed that agitation provided good mixing and improved the overall organic matter consumption rates. A modified first-order kinetic model represented adequately the data in the entire range of agitation rate. The apparent first-order kinetic constant for suspended COD rose approximately 360% when the agitation rate was changed from 500 to 900 rpm, whereas the apparent first-order kinetic constant for soluble COD did not vary significantly.     

Enhanced biodegradation of petrochemical wastewater using ozonation and BAC advanced treatment system

The characteristics of degradation/conversion of bio-refractory and the growth of a biofilm are investigated in laboratory-scale pre-ozonation and lifted moving-bed biological activated carbon (BAC) advanced treatment processes treating phenol, benzoic acid, aminobenzoic acid and petrochemical industry wastewater which contains acrylonitrile butadiene styrene (ABS). The optimal reaction time and ozone dosage of pre-ozonation for bio-refractory conversion were determined to be 30 min and 100-200 mg O3/hr, respectively. After pre-ozonation of 30 min treatment, BOD5/COD ratio of influent and effluent increased apparently from 20 to 35%, approximately. However, the change of pH in pre-ozonation was inconspicuous. The optimal flow rate of influent and air were controlled at 1.6 l/h and 120-150 nl/min in lifted moving-bed BAC advanced treatment reactor. A COD removal efficiency of 85-95% and 70-90% may be maintained by using an organic loading of 3.2-6.3 kg COD/m3 day and 0.6-1.6 kg-COD/m3 day with an HRT of 6.0 h as secondary and advanced treatment system, respectively. The time required for the BAC bed is be regenerated by a thermal regeneration is prolonged 4-5 times more than that of GAC system. It can be estimated that the enhanced COD removal capability of the biofilm was not only due to the increase in the COD removal capability of acclimated bacteria, but also due to species succession of bacteria in bio-film ecosystem.     

Development of microbial community structure and actvity in a high-rate anaerobic bioreactor at 18 degrees C

Anaerobic digestion in the psychrophilic (< 20 degrees C) or sub-mesophilic temperature range has recently been proven as an effective treatment option for the mineralization of a wide variety of problematic wastewaters. In this study, an expanded granular sludge bed-anaerobic filter (EGSB-AF) bioreactor was seeded with a full-scale, mesophilic sludge and employed to evaluate the long-term operational potential, and underlying microbial ecology, of this approach for the treatment of a medium-strength (5 g chemical oxygen demand [COD] l(-1)), synthetic, volatile fatty acid-based wastewater. Throughout the trial period of 625 days, extended intervals of consistently stable and efficient wastewater treatment were sustained. These results were highlighted by a short start-up period (21 d), low hydraulic retention times (4.88h), high organic (up to 24.64kg CODm(-3)d(-1)), and volumetric loading rates (up to 4.92 m3 m(-3) d(-1)). A stable, well-settling granular sludge bed was maintained in the bioreactor for the majority of the trial; however, reduced treatment efficiency and biomass washout were observed at an imposed OLR of 36.96 kg COD m(-3) d(-1). The microbial biomass in the bioreactor was investigated using maximum specific methanogenic activity assays and polymerase chain reaction-denaturing gradient gel electrophoresis. A temporal succession of both the bacterial and archaeal populations was noted during the trial, compared to the seed sludge, in response to bioreactor operation at lower temperatures, loading rate increases and to VFA accumulation in the bioreactor. During the trial, an increased contribution of hydrogenotrophic methanogenesis as a pathway of methane production was observed, along with the overall emergence of a highly active psychrotolerent-though still mesophilic biomass.     

Integrated anaerobic-aerobic fixed-film reactor for slaughterhouse wastewater treatment

An integrated anaerobic-aerobic fixed-film pilot-scale reactor with arranged media was fed during 166 days with slaughterhouse wastewater. Operation temperature was 25 degrees C and the anaerobic-aerobic volume ratio was decreased from 4:1 to 3:2 and finally to 2:3. Overall organic matter removal efficiencies of 93% were achieved for an average organic loading rate of 0.77 kg COD/m3 d, and nitrogen removal efficiencies of 67% were achieved for nitrogen loading rates of 0.084 kg N/m3 d. The high internal recirculation associated to the air-lift effect linked to the aeration of a part of the reactor section caused high mixing between the anaerobic and aerobic zones, so that most organic matter was removed aerobically. The nitrification process achieved an efficiency of 91% for nitrogen loads of 0.15 kg N/m3 d when the anaerobic-aerobic volume ratio was 2:3 and was limited by dissolved oxygen concentration below 3 mg/l. The influence of the heterotrophic biomass growing in the outer biofilm was checked. Denitrification only implied the 12-34% of the total nitrogen removal and was limited by dissolved oxygen concentration in the anaerobic zone above 0.5 mg/l caused by the mixing regime. Most removed nitrogen was employed in synthesis of heterotrophic bacteria.     

Effect of wastewater composition on archaeal population diversity

Distribution and occurrence of Archaea and methanogenic activity in a laboratory scale, completely mixed anaerobic reactor treating pharmaceutical wastewaters were investigated and associated with reactor performance. The reactor was initially seeded with anaerobic digester sludge from an alcohol distillery wastewater treatment plant and was subjected to a three step feeding strategy. The feeding procedure involved gradual transition from a glucose containing feed to a solvent stripped pharmaceutical wastewater and then raw pharmaceutical wastewater. During the start-up period, over 90% COD removal efficiency at an organic loading rate (OLR) of 6 kg COD m(-3)d(-1) was achieved with glucose feeding, and acetoclastic methanogenic activity was 336 ml CH4 gTVS(-1)d(-1). At the end of the primary loading, when the feed contained solvent stripped pharmaceutical wastewater at full composition, 71% soluble COD removal efficiency was obtained and acetoclastic methanogenic activity decreased to half of the rate under glucose feed (166 ml CH4 gTVS(-1)d(-1)). At the end of secondary loading with 60% (w/v) raw pharmaceutical wastewater, COD removal dropped to zero and acetoclastic methanogenic activity fell to less than 10 ml CH4 gTVS(-1)d(-1). Throughout the course of the experiment, microbial community structure was monitored by DGGE analysis of 16S rRNA gene fragments. Five different archaeal taxa were identified and the predominant archaeal sequences belonged to methanogenic Archaea. Two of these showed greatest sequence identity with Methanobacterium formicicum and Methanosaeta concilii. The types of Archaea present changed little in response to changing feed composition but the relative contribution of different organisms identified in the archaeal DGGE profiles did change.     

Application of a membrane bioreactor for treating explosives process wastewater

A bench-scale anoxic membrane bioreactor (MBR) system, consisting of a bioreactor coupled to a ceramic cross-flow ultrafiltration module, was evaluated to treat a synthetic wastewater containing alkaline hydrolysis byproducts (hydrolysates) of RDX. The wastewater was formulated the same as hydrolysis wastewater and consisted of acetate, formate and formaldehyde as carbon sources and nitrite and nitrate electron acceptors. The MBR system removed 80-90% of the carbon sources, and approximately 90% of the stoichiometric amount of nitrate, 60% of nitrite. The reactor was also operated over a range of transmembrane pressure, temperature, suspended solids concentration, and organic loading rate to maximize treatment efficiency and permeate flux. Increasing the transmembrane pressure and temperature did not improve flux significantly. Increasing mixed liquor volatile suspended solids (MLVSS) concentration in the bioreactor decreased the permeate flux significantly. The maximum volumetric organic loading rate was 0.72 kg COD/m3/day. The maximum food-to-mass ratio was 0.50 kg N/kg MLVSS/day and 1.82 kg COD/kg MLVSS/day. Membrane permeate was clear and essentially free of bacteria, as indicated by heterotrophic plate count. Permeate flux ranged between 0.15 and 2.0 m3/m2 day and was maintained by routine backwashing every three days. Backwashing with tap water containing chlorine bleach every fourth or fifth backwashing was able to restore membrane flux to its original value.     

Biofilm growth and characteristics in an alternating pumped sequencing batch biofilm reactor (APSBBR)

A novel biofilm reactor-alternating pumped sequencing batch biofilm reactor (APSBBR)-was developed to treat synthetic dairy wastewater at a volumetric chemical oxygen demand (COD) loading rate of 487 g COD m(-3) d(-1) and an areal loading rate of 5.4 g COD m(-2) d(-1). This biofilm reactor comprised two tanks, Tanks 1 and 2, with two identical plastic biofilm modules in each tank. The maximum volume of bulk fluid in the two-tank reactor was the volume of one tank. The APSBBR was operated as a sequencing batch biofilm reactor with five operational phases-fill (25 min), anoxic (9 h), aerobic (9 h), settle (6 h) and draw (5 min). The fill, anoxic, settle and draw phases occurred in Tank 1. In the aerobic phase, the wastewater was circulated between the two tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by micro-organisms in the biofilms when they were exposed to the air. In this paper, the biofilm growth and characteristics in the APSBBR were studied in a 98-day laboratory-scale experiment. During the course of the study, it was found that the biofilm thickness (delta) in Tank 1 ranged from 1.2 to 7.2 mm and that in Tank 2 from 0.5 to 2.2 mm; the biofilm growth against time (t) can be simulated as delta=0.07t0.99 (R2 = 0.97, P = 0.002) in Tank 1 and delta = 0.08t0.66 (R2 = 0.81, P = 0.04) in Tank 2. The biomass yield coefficient, Y, was 0.18 g volatile solids (VS) g(-1) COD removal. The biofilm density in both tanks, X, decreased as the biofilm thickness increased and can be correlated to the biofilm thickness, delta .     

Soil aquifer treatment of artificial wastewater under saturated conditions

A 2000 mm long saturated laboratory soil column was used to simulate soil aquifer treatment under saturated conditions to assess the removal of chemical and biochemical oxygen demand (COD and BOD), dissolved organic carbon (DOC), nitrogen and phosphate, using high strength artificial wastewater. The removal rates were determined under a combination of constant hydraulic loading rates (HLR) and variable COD concentrations as well as variable HLR under a constant COD. Within the range of COD concentrations considered (42 mg L⁻¹-135 mg L⁻¹) it was found that at fixed hydraulic loading rate, a decrease in the influent concentrations of dissolved organic carbon (DOC), biochemical oxygen demand (BOD), total nitrogen and phosphate improved their removal efficiencies. At the high COD concentrations applied residence times influenced the redox conditions in the soil column. Long residence times were detrimental to the removal process for COD, BOD and DOC as anoxic processes and sulphate reduction played an important role as electron acceptors. It was found that total COD mass loading within the range of 911 mg d⁻¹-1780 mg d⁻¹ applied as low COD wastewater infiltrated coupled with short residence times would provide better effluent quality than the same mass applied as a COD with higher concentration at long residence times. The opposite was true for organic nitrogen where relatively high concentrations coupled with long residence time gave better removal efficiency.