Biological treatability of dairy wastewaters

Biological treatability of an integrated dairy plant wastewater containing a small fraction of whey-washwaters mixture has been experimentally investigated. Emphasis has been placed on the assessment of the initially inert fraction, S₁ and soluble residual microbial products, S_p. Parallel batch experiments have been conducted to determine the kinetic and stoichiometric coefficients of the degradable COD. The results have shown that the wastewater tested had practically no initially inert fraction, but generated residual microbial products amounting to 6–7% of the initial degradable COD. The results obtained have been fed into a set of equations describing the steady state operation of an activated sludge system with sludge recycle and a relationship indicating the variation of the total effluent COD with the sludge age has been defined for the wastewater tested. It is noted that effluent COD cannot be biologically reduced below 85 mg l⁻¹, regardless of the sludge age, due to generation of residual fractions.     

A comprehensive study on the biological treatabilities of phenol and methanol—I. Analysis of bacterial growth and substrate removal kinetics by a statistical method

An unbiassed statistical method was developed to evaluate kinetic parameters in the biological oxidation of wastewaters. Through the statistical analyses of the biological oxidation kinetics, it was shown that the kinetic equations satisfactorily described the bacterial growth and substrate removal kinetics where X is biomass concentration, S is substrate concentration, t is time, a is cell yield coefficient, k_d is cell decay coefficient, K_s is Michaelis-Menten constant, and k is substrate removal rate coefficient. The coefficients K_s and a changed with temperature insignificantly while k and k_d were closely related to it. The temperature independent coefficients K_s and a were estimated to be 236 mg 1⁻¹ (standard deviation, σ = 70 mg 1⁻¹) and 1.21 (σ = 0.06) respectively for phenol, and 2330 mg 1⁻¹ (σ = 1410 mg 1⁻¹) and 1.25 (σ = 0.45) respectively for methanol based on total organic carbon (TOC) and volatile suspended solids (VSS). The oxygen utilization rate can be formulated as where Rr is the oxygen utilization rate (mg 1⁻¹ O₂ time⁻¹), as′ is a coefficient designating oxygen requirement per substrate utilized, and b′ is a coefficient designating oxygen requirement per biomass for endogeneous respiration. The coefficient a′ was 1.39 for phenol and 2.23 for methanol, and b′ was 1.42 k_d for both substances based on TOC and VSS.     

Palm oil refinery wastes treatment

Effluent from the refining of crude palm oil was subjected to physical-chemical and biological treatment. An inclined corrugated parallel plates oil separator spaced at 25 mm was used with hydraulic loading rates of 0.2, 0.5 and 1 m³ m⁻²-h. 91% oil and grease removal could be achieved at 0.2 m³ m⁻²-h. Coagulation and flocculation carried out on batch samples after oil and grease separation revealed that with 100 mg l⁻¹ alum addition BOD was reduced from 3500 to 450 mg l⁻¹ and COD from 8600 to 750 mg l⁻¹ after 30 min settling. Higher doses of alum and doses of polyelectrolyte, activated carbon and sodium hypochloride did not yield significant additional reductions in BOD and COD. Batch dissolved air flotation (DAF) removed 90% of the suspended solids with 2.7% solids in the thickened sludge at an A/S ratio of 0.014. This method yielded the similar effluent quality as the inclined corrugated plates oil and grease separator. Field data from a DAF plant compare closely with data achieved in this study. Activated sludge treatment on the effluent from the oil separator yielded a BOD of 46 mg l⁻¹ with a loading rate of 0.3 g BOD (g MLVSS)⁻¹-day. Total dissolved solids (TDS) remained high and removal through coagulation and chemical oxidation brought the COD level down to around 180 mg l⁻¹. Biokinetic coefficients Y, k_dK and K₃ were found to be 0.85 g VSS (g BOD)⁻¹, 0.016 day⁻¹, 0.12 g BOD (g VSS)⁻¹-day and 510 mg l⁻¹ BOD respectively.     

Long-term effects of treated domestic wastewater on brown trout

A 12-month bioassay was conducted to determine the effects of unchlorinated, treated, domestic wastewater on survival, growth, swimming performance, and gill tissue of brown trout (Salmo trutta). Ammonia was the toxicant of concern, because the facility's effluent periodically exceeded the U.S. Environmental Protection Agency's (EPA) recommended criterion. Juvenile brown trout (initial weight = 2 g), which were exposed to six concentrations (0–37%) of effluent, were fed a restricted ration, so that growth rates were similar to those of wild stream residents. At the highest effluent concentration, monthly mean concentrations of un-ionized ammonia ranged from 0.004 to 0.055 mg l⁻¹ NH₃---N (at. wt = 14); these concentrations exceeded the EPA criterion of 0.016 mg l⁻¹ about 40% of the time. There were no significant effects of effluent concentration on survival, growth, or swimming performance of brown trout, but the degree of damage to gills was directly related to effluent concentration.     

Effects of mixing velocity on anaerobic fixed film reactors

Four laboratory-model upflow anaerobic fixed film reactors (AFFR 1, 2, 3 and 4) treating landfill leachate were subject to identical volumetric organic load (7 kg COD m⁻³ d⁻¹) and hydraulic retention time (3d), but the contents in each unit were continuously recirculated for 10 months at four different velocities, respectively, of 21, 66, 680 and 3063 cm h⁻¹. The objective was to assess the effects of such mixing velocities (ν) on COD removal efficiencies (E), mean cell residence time (MCRT) and substrate utilization rate (U expressed as g COD removed d⁻¹ g⁻¹ VSS). The results showed that the relationships between E and ν and MCRT and ν were inverted U-shaped curves. The two middle reactors (AFFR 2 and 3) had near-optimum velocities (ν₂ and ν₃) with maximum E values of 88–89%. AFFR 4 had a high value of ν scouring biofilm on the biorings, resulting in higher concentrations of SS, VSS and COD in the effluent. All four reactors had nearly similar values of U (1.85–2.14 g COD d⁻¹ g⁻¹ VSS). The value of ν₁ (AFFR 1) was too low to enhance performance and ν₄ was too high to retain the biomass. The optimum recycle velocity, under the test conditions, was in the range of 66–680 cm h⁻¹.     

Treatment of poultry manure wastewater using a rotating biological contactor

A pilot scale, six stage rotating biological contactor was used to evaluate the feasibility of this process for the stabilization of liquid animal manures. Total disc surface area was approx. 16.7 m². Treatment efficiencies were determined at various waste strengths and influent flow rates.With loading rates of 14.7–322 g m⁻² day⁻¹, the average COD reduction was 61%. With loading rates of 4.88-24.4 g m⁻² day⁻¹, the average BOD₅ reduction was 87%. Total nitrogen removal averaged approximately 30% for the entire study. Mixed liquor oxygen uptake rates were generally in excess of 80 mg 1⁻¹ h⁻¹.Clarified effluent was non-odorous and suitable to be reused for manure flushing or spray irrigation. Treatment was not sufficient to permit effluent discharge to surface waters.     

Calibration of a model for an A + B acivated sludge pilot plant treating industrial wastewater

A mathematical model has been developed and calibrated for a two-stage (A + B) activated sludge pilot plant treating wastewater from a chemical-pharmaceutical industry. Two series of simulations have been performed: (a) by using typical values for the parameters of the model from the bibliography, which remain constant with time, and (b) by using, for some parameters, values which are variable with time, and are determined following a specific methodology. The calibration is constrained to be exactly consistent with daily observations of COD from the effluent and reactor suspended solids (MLSS). Three internal parameters of the system were thus obtained in their daily variation: MLSS growth rate, specific substrate removal rate and concentration factor in the settling tank. Mean values obtained for MLSS growth rate were 0.73 d⁻¹ and 0.022 d⁻¹ for reactors A and B respectively, and the average observed biomass yield coefficient was 0.38 (reactor A) and 0.21 (reactor B). The model infered the evolution of the COD and MLSS with a fairly good accuracy, proving that the method used to obtain the parameters does not have internal inconsistencies and may be used in other situations.     

Silage effluent digestion by an upflow anaerobic filter

Silage effluent is generally regarded as one of the major agricultural pollutants of water courses. Efficient anaerobic digestion of silage effluent was achieved by a 3-day hydraulic retention in an upflow anaerobic filter. The filter was a laboratory scale unit containing a limestone chip support matrix. At loading rates ranging from 7.8 to 14.2 kg COD m⁻³ active volume day⁻¹, the average COD removal obtained ranged from 86 to 89% with a TOA removal of 82–88%. The methane content of the biogas produced ranged from 81 to 88%. The rate of COD conversion to CH₄ was independent of the loading rate under the conditions tested and the observed efficiency averaged 0.357 m¹ CH₄(STP) kg⁻¹ COD introduced to the reactor.The reactor tolerated considerable variation in influent pH without any apparent decrease in digestion efficiency. It is apparent from the results obtained that a reactor which is in routine use for slurry digestion may also be utilised for silage effluent digestion on a seasonal basis.     

Control of phenol in biological reactors by addition of powdered activated carbon

A biological reactor containing a pure culture of E. coli was subjected to a variety of feed upsets involving phenol with powdered activated carbon applied as a control mechanism. The amount and rate of addition of the carbon was varied to evaluate the effectiveness of this strategy for maintaining the effluent quality. It was found that the carbon addition greatly reduced the magnitude of concentration transients and permitted operation with an input phenol concentration above 1000 mg 1⁻¹.     

A mercury-free accelerated method for determining the chemical oxygen demand of large numbers of water samples by autoclaving them under pressure with acid-dichromate

In order to fulfill the objective of a water control program based on frequent sampling in several wastewater treatment plants, rivers and lakes a simplified method for measuring COD was developed. The procedure, in this article called the RR-method, includes: small sample and reagent volume; rapid addition of a mixture of all reagents to the sample; exclusion of mercury; autoclaving at 120°C for 1 h in flasks with fitted glass stoppers. To avoid dilution before analysis the method has been adapted for wastewater (I: 10–300 mg O₂ l⁻¹) and fresh water (II: 10–100 mg O₂ l⁻¹).Parallel analyses on different types of water samples according to Standard Methods showed that the yield by the RR-method was about 10% lower (Table 2). With water from the wastewater treatment plant at Uppsala (COD around 20 mg O₂ l⁻¹), the two methods gave an identical result. The somewhat lower yield was mostly due to decreased dichromate concentration and oxidation temperature. The lower oxidation potential made correction for chloride interference unnecessary below 1 g Cl⁻ l⁻¹ (Table 1).The RR-method also showed a good correlation to the values for KMnO₄-consumption. Parallel analyses of 318 samples from 14 wastewater receiving lakes gave the correlation coefficient r = +0.90 (Fig. 1).     

A modified Activated Sludge Model to estimate solids production at low and high solids retention time

In this paper, a modified version of the IWA-ASM1 model capable of correctly simulating the production of solids over a wide range of solids retention time (SRT) is presented. The parameters of the modified model have been estimated by integrating the results of respirometric and titrimetric tests with those of studies conducted on pilot scale plants that treat industrial wastewaters of differing characteristics.On the basis of the experimental results and their subsequent processing, it appears that the production of solids may be satisfactorily estimated using the modified model in which fractions X_P and X_I are supposed to be hydrolysable with a first-order kinetic.In the cases that were examined, the constant of the aforementioned kinetics was estimated to be k_i = 0.012 d⁻¹ and k_i = 0.014 d⁻¹, for tannery and textile wastewater respectively.A reliable calibration of the parameter k_i was possible when data relative to the experiment conducted in the pilot plants for no less than 60 d and in conditions of complete solid retention was utilized.     

Sources and behaviour of dinitrotoluene isomers in sea-water

The sources and behaviour of dinitrotoluene (DNT) isomers in the sea-water of Dokai Bay in Japan were investigated. DNT isomers such as 2,6-, 2,5-, 2,4-, 2,3- and 3,4-DNT were identified in an industrial effluent. One drain, the main source, discharged about 150 kg of DNT isomers as the maximum value in a day. This value roughly agrees with that obtained from seven months of monitoring of DNT isomers in sea-water. The monitoring revealed that about 76 kg of DNT isomers was discharged into the bay daily. 2,6-, 2,4- and 2,3-DNT were detected in the sea-water at the levels of 14,8-ND μg l⁻¹ (n = 82), 206-ND μg l⁻¹ (n = 82) and 0.412-ND μg l⁻¹ (n = 82), respectively. The relationship between the concentration of 2,4-DNT (Y) and the distance (X) is statistically expressed by the equation of Y = (6.38 ± 4.02)e^{−(0.269 ± 0.044)X}, and the relationship between the 2,6-DNT/2,4-DNT ratio (y) and the distance (X) is expressed as y = −(0.795 ± 0.131) X + (9.35 ± 4.1). These relationships reveal that the decrease of DNT isomers in the sea-water is caused by factors more complex than mechanical dilution by tidal action.     

Towards a better understanding of high rate biological film flow reactor theory

On the assumption that performance of biological film flow reactors is independent of oxygen transfer, a theoretical extension of a mathematical model (after Ames) is described. This predictive and interpretive model incorporates both mass transfer-limitations between biomass and liquid film, and kinetic biological reaction rate of organic “food” utilization.Given general boundary conditions for the differential equations describing the mass transfer process, it is shown that: C_e = C_r + (C_l − C_r.exp(−K_m D/Q) where by definition: C_t = α C_s + C_r1/K_m = 1/K_LA_γ + α/Kx.For an influent concentration biochemical oxygen demand (C_i) and resultant effluent concentration (C_e) obtained during film flow through a packed media depth (D), the Model proposes that the residual concentration (C_r) is a function of surface irrigation rate (Q) and biomass activity. If this term is negative, adsorption occurs; while if positive, desorption from the biomass film at concentration (C_s) takes place.An overall mass transfer coefficient (K_m) is defined by a series equation where the usual mass transfer coefficient (K_L) is primarily a function of Reynolds Number [surface irrigation rate (Q) and specific surface area (A_V)], Schmidt Number (diffusivity of organic “Food”) and concentration. “Food” utilization at active sites on the biological film is governed by a specific adsorption coefficient (α) and explained by a Langmuir analogy. Biological conversion of “food” is described by a kinetic rate constant (K), while the necessary oxygen is defined by (X).This predictive model was developed from a wide range of pilot plant data, successfully tested further on a variety of published results and on actual full scale operating plants.Parameters derived from this Model, in terms of Height of Transfer Unit and Kinetic Reaction coefficient, characterize organic “treatability” for a variety of wastes.     

Études des transformations des formes du carbone, azote, phosphore, soufre et des principaux éléments minéraux au cours de la mesure de la demande totale en oxygene—III transformation des formes du soufre

Previous experiments carried out with the laboratory TOD meter Ionics 225 of the DOW Chèmical made it possible (after a high temperature catalytic action) to characterize the stable forms of organic and inorganic carbon and nitrogen (NH₄⁺, NO₂⁻, NO₃⁻), and the principal cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) in the course of the total oxygen demand (TOD) measurement.The object of this study is firstly to compare the oxidation capability of different techniques of organic pollution (particularly the COD and TOD) in relation to the constituent elements of the organic matter C, N, P, S, and to calculate the possible interferences of the inorganic compounds at the time of TOD test.These investigations warrant the application of this technique to measure the amount of organic pollution in relatively mineralized conditions (Industrial wastewater, sea-water…). The present publication is concerned more with the study of the transformation of the organic and inorganic sulphur forms (S²⁻, SO₃²⁻. SO₄²⁻) in the course of the TOD measurement.The study of the oxidizability of the organic sulphur compound type C_xH_yO_zS, made it possible to establish a specific relation with a ratio of 0–50 mg of organic sulphur l⁻¹, between the oxygen demand of this element [TOD (S)] and its concentration (TOD (S) = 0.97 [S]).These tests showed a partial oxidation of the sulphur to SO₂ and SO₃ as the literature claimed. On the other hand, the oxidation of the same compounds during the COD tests varies greatly and although it is not possible to establish a correlation between these two measurements, as applies in the case of organic nitrogen, nevertheless these experiments showed a greater reliability of the TOD compared with the COD in the oxidation of organic matter in general. We then carried out experiments on the different mineral forms of sulphur in order to distinguish the possible effects and to recommend simple improvements.A relative study on sulphate ions had been carried out with standard solutions which have the same TOD (the basic TOD is obtained using potassium phthalate acid) and the same increasing concentration of the salt M₂SO₄ type. The experiments showed that the basic TOD decreases when the concentration of sulphate ions is increased (Fig. 3). Therefore, the interference is negative and taking into consideration the specific oxygen demand of the cation, we can propose an evaluation of this interference (ΔTOD (SO₄²⁻) = 0.203 [SO₄²⁻]). The same experiments have been conducted with a salt of M₂SO₃ type and similar results obtained (Fig. 5).The specific interference of the sulphite ion is negative and can be estimated by the following equation (ΔTOD (SO₃²⁻) = 0.132 [SO₃²⁻]). In both cases, we have to note that the transformation of these inorganic anions occurs between those relative to the theoretical dissociation reaction corresponding to the appearance of the oxide SO₂ and SO₃. For sulphurous on the contrary, the interference is positive and therefore corresponds to an extra oxygen demand (Fig. 8).The experiments were conducted directly with the M₂S salts (M representing K or Na) in aqueous solution.The evaluation of this interference had been made in the consideration of two concentration ranges of the sulphurous ions (0–35 mg S²⁻ l⁻¹): TOD (S²⁻) = 0.4 [S²⁻] and (35–100 mg S²⁻ l⁻¹): TOD (S²⁻) = 1.2 [S²⁻] − 30.Therefore this study confirms a better oxidation of the organic matter by TOD test in comparison with COD test.But sulphate and sulfite have a negative interference in the TOD measurement, whereas sulphurous is positive.The evaluation model of these interferences allows a correction to be made of the TOD value or to verify TOD measurement of organic pollution obtained by this technique.     

Effects of influent substrate concentration on the kinetics of natural microbial populations in continuous culture

In order to determine whether the influent substrate concentration exerts an effect upon the kinetics of soluble substrate removal by natural microbial populations growing in continuous culture experiments were run using a multicomponent substrate. A two-level factorial experimental design was employed with reactor dilution rate and influent substrate concentration as the independent variables. Analysis of the results indicated that both variables exerted a significant effect (1% level) upon the effluent soluble COD. It was possible to model the system using the linear approximation of the Monod equation resulting in an equation of the general form: S=K′S₀D + K″S₀The findings of the study indicate that engineers responsible for the design and operation of wastewater treatment facilities should consider the influent substrate concentration when choosing a mean cell residence time for the system.     

Treatment of low strength domestic wastewater using the anaerobic filter

A laboratory scale anaerobic filter packed with synthetic high surface area trickling filter media was used to treat a low strength domestic wastewater averaging 288 mg 1⁻¹ COD. The filter was operated for 60 days after reaching steady-state at 20, 25, 35°C at a loading rate of 0.02 lb COD ft⁻³ day⁻¹ and 24 h hydraulic retention time. Filter effluent BOD₅ averaged 38 mg 1⁻¹ providing an average removal rate of 79%, and effluent COD averaged 78 mg 1⁻¹, corresponding to a 73% removal rate. Removal efficiencies showed very little sensitivity to daily fluctuations in influent wastewater quality. The filter performance at 25 and 35°C was not significantly different, but BOD and TSS removal efficiency declined a: 20°C. Gas production averaged 0.027 ft⁻³ of gas per ft³ of influent wastewater, or 1.875 ft³ of gas per pound of influent COD. Gas composition averaged 30% nitrogen, 65% methane, and 5% carbon dioxide. Ammonia nitrogen and sulfides both increased during treatment. It is concluded that the anaerobic filter is a promising candidate for treatment of low strength wastewaters and that post treatment for sulfides and ammonia may be necessary.     

Effect of phenol on oxygen uptake rate of a laboratory population of Chironomus attenuatus (walk.)

A laboratory population of fourth-instar larval forms of Chironomus attenuatus Walker received a continuous life-long exposure of 0, 2.8, 8.2, 11.2, 16.3, and 22.4 ppm phenol. Measurements were taken of water temperature, pH, and dissolved oxygen concentration. Larvae exposed to the different phenol concentrations were analyzed for oven-dry weight and ash-free weight. The oxygen uptake was determined. The regression of oxygen uptake (Y), adjusted for phenol level, pH, and oxygen concentration, on ash-free weight (X) was log Y = 0.173–0.478 log X. The regression of adjusted oxygen uptake (Y) on phenol concentration (X) was Y = 1.632 + 0.299 log X. Calories lost through respiration (Y) were related to phenol level (X) by the equation, Y = (2.10 × 10^?3) + (3.86 × 10^?4) log X. The ash-free weight per individual (Y) decreased with increasing phenol concentration (X) as explained by the equation, Y = 0.753 ? 0.114 log X.     

A comprehensive study on the biological treatabilities of phenol and methanol—III Treatment system design

The effects of temperature, pH, salinity, and nutrients on bacterial activities were investigated and evaluated using a statistical method. The substrate utilization rate coefficient (k) decreased as pH deviated from neutral and as salinity increased, and the unfavorable pH and salinity alleviated the temperature effect on k. The modified Arrhenius equation, k_T2 = k_T1 θ(^T2−T1), was not effective in describing the temperature effect on k: the temperature coefficient (θ) ranged between 1.0–1.4 depending on the temperature range, pH, salinity, and substance (phenol or methanol). The endogeneous respiration activity was affected by various environmental factors such as pH, temperature, and salinity; however, the cell decay coefficient (k_d) turned out to be correlated to a single parameter, k. Thus, k_d = 0.066 k^0.87 and k_d = 0.0115 k^0.634, where k and k_d are based on the unit of h⁻¹, were proposed for the prediction of cell decay coefficient for phenol and methanol acclimated activated sludge, respectively. In batch treatment of 770 mg l⁻¹ of phenol and 1000 mg l⁻¹ of methanol as TOC, nitrogen and phosphorus did not have any recognizable effect on k, while trace elements such as Fe²⁺, Mg²⁺, Mn²⁺, Ca²⁺, and Zn²⁺, etc. showed a slightly perceptible effect on it. The absence of extra-cellular nitrogen and phosphorus resulted in a greater cell yield; however, the cells in this condition decayed more rapidly than normal cells. The primary factor affecting the substrate decomposition rate in natural systems was pH: phenol decomposition resulted in a considerable decrease in pH so that the buffering capacity of the water was the most important factor, and methanol decomposition did not affect pH significantly so that the initial pH of the water was the most important factor. An initial lag phase was observed in 8 out of 115 phenol batch tests and 31 out of 66 methanol batch tests.     

An evaluation of the potential toxicity of treated bleached kraft mill effluent to striped bass (Morone saxatilis walbaum) larvae exposed through metamorphosis to the juvenile stage

Twenty-day-old striped bass (Morone saxatilis) larvae were exposed to a range of treated bleached kraft mill effluent (BKME) concentrations from 0 to 20% effluent by volume (v/v) under continuous flow test conditins. The experimental test concentrations in the 2–20% BKME test aquaria had a BOD₅ which ranged from < 1 to 5 mg l⁻¹, TSS 12–17 mg l⁻¹, and true color 35–416 mg l⁻¹. Bleached kraft mill effluent did not kill larvae exposed to it for 20 days through metamorphosis to the juvenile stage. The BKME did not alter growth in length, weight or condition factor in larvae over the 20-day exposure period as determined by multiple regression analysis. A linear regression analysis on the dry weight data at Day 20 only, however, indicated a trend of decreasing weight with increasing BKME concentration. Effluent-exposed larvae also developed normally during the 20-day study. All individuals examined completed the transformation from postlarvae to juveniles by the age of 40 days.     

Fermentation of food industry wastewater

Treatment of wastewater formed during production of citric acid and fodder yeast was carried out under dynamic conditions on a laboratory scale in an anaerobic upflow biofilter. The bioreactor was run at a temperature of 36°C. Methane fermentation of wastewater from citric acid production proceeded with a high yield. Removal of 73% COD and 73% BOD₅ was achieved at a biofilter loading rate of 3.16 kg COD/m³ d and a 48-h hydraulic retention time of the wastewater. In addition, 65 and 70% reductions of COD and BOD₅, respectively, were attained with respect to wastewater from fodder yeast production at a biofilter loading rate of 3.00 kg COD/m³ d and a 60-h hydraulic retention time. The methanogenesis process yielded 0.32 m³ CH₄/kg of removed COD for citric acid wastewater and 0.34 m³ CH₄/kg of removed COD for wastewater from the fodder yeast production plant. Microbiological reduction amounting to 50% of sulphates was found to occur in wastewater from the fodder yeast production plant at an initial sulphate concentration of about 4500 mg SO₄²⁻/dm³.As determined by Oleszkiewicz's formula, the specific coefficients of the reaction rates, k, were 2.90 and 2.02 kg COD/m³ d depending on the type of wastewater. Consequently, it has been shown that the anaerobic upflow biofilter is suitable for treating wastewater produced during molasses processing. Attention should also be drawn to its unique and simple construction and the relatively low power demand required to operate this unit. Wastewater recirculation was not required in the unit.