In-Situ sediment oxygen demand in five Southwestern U.S. lakes

In-situ sediment oxygen demand (SOD) was measured for five southwestern lakes from 1985 to 1988. Age, morphometry and trophic states varied among the lakes but all were thermally stratified and had anoxic hypolimnia during summer months. SOD measurements were obtained with a hemispherical, sealed chamber-type benthic respirometer fitted with a submersible recirculation pump and a sensor package for recording dissolved oxygen, temperature, conductivity and pH. SOD measurements were obtained at between two and four sites on most lakes. Temperature corrected values ranged from 0.34 to 9.02 g O₂/m²·day. These data significantly expand the currently limited accessible SOD data base for Southwestern lakes.     

The relation between redox potential and denitrification in a water-sediment system

In the overlying water of a water-sediment system the pH was controlled at 7.0, the nitrate-nitrogen concentration at 25.0 mg 1^?1 and the dissolved oxygen concentration above 6.1 mg t^?1. The temperature of the whole system was kept at 15°C. The average rate of nitrate removal from the system as a result of denitrification amounted to 160 mg NO₃^? -N m^?2 day^?1. By means of Eh measurements at various depths in the sediment, it was attempted to figure out the course of the penetration fronts of nitrate and oxygen in the sediment during 241 days of incubation. From these results the layer in which denitrification occurred was derived. The course of the denitrification zone was followed during the incubation period. As a result of the depletion of the available hydrogen donors in the sediment, oxygen reached the bottom of the sediment after 235 days of incubation.     

Effects of carbon dioxide deficiency and metal toxicity on biological oxygen demand

In this study, the effects of carbon dioxide (CO₂) deficiency on the biological growth under respirometric conditions, first‐ and second‐order biological oxygen demand (BOD) progressions using two different BOD measurement techniques and metal toxicity effects on the respirometric BOD are investigated. The effects of CO₂ deficiency in the growth of bacteria and related effects on the first‐ and second‐stage BOD progressions are investigated using various media with respirometers in comparison with the BOD dilution method. CO₂ deficiency causes significant retardations on the growth of bacteria and the second‐stage respirometric BOD values are suppressed. CO₂ seems to be an essential nutrient for the growth of microorganisms and for the oxygen uptake progressing rates. HgCl₂, HgSO₄, CuSO₄, K₂Cr₂O₇, ZnSO4 and Al₂(SO₄)₃ inorganic metal compounds cause significant retardations in the respirometric BOD values obtained from a synthetic autotrophic medium. Effects are found to be dependent on the applied concentrations of these chemicals in the medium.     

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.     

Leachate treatment with nitrification of ammonia

Results are presented on the treatment of leachate to remove ammonia by biological nitrification. Outdoor activated sludge and trickling filter pilot plants were operated for 2 years at a major co-disposal landfill. Leachate ammonia nitrogen concentrations ranged from 150 to 550 mg l^?1 while TOC concentrations ranged from 200 to 500 mg l^?1. Very little of the TOC was degradable and BOD: NH₃-N ratios were typically 1:3.Nitrification was successfully established in both plants, and curves were established for the response of the kinetics to different temperatures. Maximum ammonia removal rate in the activated sludge plant was at least 131 g N kg VSS^?1 day^?1 achieved at an average temperature of 13°C. Maximum removal rate in the trickling filter was 309 mg N m^?2 day^?1, at 16°C.Operating problems and strategies for full-scale treatment are discussed.     

Field analysis of PSA O2–ozone production process for water recycling

The use of an oxygen generator based on pressure swing adsorption technology (PSA) has been investigated as an alternative method for supplying oxygen for onsite ozone production. During the investigation period of 1040 h, the oxygen purity from the PSA process fluctuated within a range of 90.5–93 O₂% (v/v). Using the working ratio of 2.8 mol of O₂ to 1 m³ of raw water, the PSA process in series with a corona discharge ozone generator yielded an oxidation–reduction potential of ca. 200 mV and a concentration of 22.8 mg/L dissolved oxygen. The average efficiency of the raw water treatment was as follows: 47% chemical oxygen demand removal, 78% biological oxygen demand removal, 36% sulphide removal and 34% colour removal. The operating cost of the PSA O₂ generation was reduced 3 times compared with the cost of high‐pressure oxygen cylinders.     

Gas production in aquatic sediments in the presence and absence of nitrate

In the overlying water of a water-sediment system the pH was controlled at 7.0, the nitrate-nitrogen concentration at 25.0 mg 1⁻¹ and the dissolved oxygen concentration above 6.1 mg t⁻¹. The temperature of the whole system was kept at 15°C. The average rate of nitrate removal from the system as a result of denitrification amounted to 160 mg NO₃⁻ -N m⁻² day⁻¹. By means of Eh measurements at various depths in the sediment, it was attempted to figure out the course of the penetration fronts of nitrate and oxygen in the sediment during 241 days of incubation. From these results the layer in which denitrification occurred was derived. The course of the denitrification zone was followed during the incubation period. As a result of the depletion of the available hydrogen donors in the sediment, oxygen reached the bottom of the sediment after 235 days of incubation.     

The role of benthic films in the oxygen balance in an East Devon river

A portable respirometer has been used to measure oxygen uptake and production rates, by fixed and suspended organisms in an East Devon river which receives papermill effluent. Benthic respiration dominates the oxygen balance in the stretch most affected by the effluent and increases the effective BOD decomposition rate by a factor of up to 12: Values of decomposition rate of 3.5–4.5 (day⁻¹) have been measured in the stream.     

Factors affecting the denitrification rate in two water-sediment systems

Effects of temperature, oxygen and nitrate concentrations of the overlying water, and the thickness of the sediment layer on the rate of denitrification in the sediment were investigated in two water-sediment systems, A and B. At 4°C, denitrification started after a prolonged lag period in contrast to nitrification which did not occur significantly. At 15°C, and particularly at 25°C, both processes proceeded readily. The disappearance of NO₂⁻ - N from the overlying water was more rapidly than that of NO₃⁻ - N.The denitrification rate was slightly reduced by increasing the dissolved oxygen concentration in the overlying water from 0 to approximately 2 mgl⁻¹. A further rise of the dissolved oxygen concentration had no further decreasing effect on the denitrification rate.The denitrification rate in sediment was dependent on the nitrate concentration in the overlying water approximating first order kinetics at lower concentrations, gradually becoming independent of the nitrate concentration at higher nitrate contents (zero order kinetics).When starting with a nitrate-nitrogen concentration of 25.2 mgl⁻¹, a sediment layer of 7 mm with A and 14 mm with B was roughly found to be involved in denitrification.Denitrification rates found in the present laboratory experiments were supposed to be considerably lower than those occurring under natural conditions as additional mechanisms for the transport of nitrate into sediments occurred in natural environments.     

Effect of temperature and dissolved oxygen on biodegradation of nitrilotriacetate

The effect of temperature and dissolved oxygen on the rate of biodegradation of nitrilotriacetate (NTA) was examined in water samples collected from the Rur River. Biodegradation of NTA was first order with respect to NTA concentration over a concentration range of 50–1000 μg l⁻¹. First order rate constants showed a typical temperature dependency (temperature coefficient, Q₁₀ = 2) and biodegradation of NTA was observed over a temperature range of 2–24°C. The effect of temperature on the rate of NTA biodegradation was described by the Arrhenius equation, with calculated activation energies in the range reported for ordinary enzyme reactions. Biodegradation of NTA was also observed at low dissolved oxygen concentrations (0.3 mg l⁻¹), although at reduced rates compared to high oxygen concentrations (13 mg l⁻¹). Biodegradation of NTA was oxygen-dependent, suggesting an obligate oxygen requirement for the initial steps in NTA metabolism by natural microbial communities in surface waters. In general, our results indicate that NTA biodegradation will occur in natural waters under conditions of low temperature and low dissolved oxygen and also at low NTA concentrations.     

A design model for nitrification on structured cross flow plastic media trickling filters

An empirical model has been developed to predict the effluent ammoniacal nitrogen concentration from structured cross flow plastic media trickling filters operated over the range of BOD loadings 0.12–0.38 kg/m³/day and ammoniacal nitrogen loadings of 0.06–0.23 kg/m³/day. The model gives good predictions based on 24‐h average effluent concentrations over a range of filter depths, organic and hydraulic loading rates. When incorporated with suitable hydraulic models, effluent ammoniacal concentration can be predicted through the diurnal range. The data gathering for the model included depth profiles on three filters. These have shown that at all but the very highest BOD loadings, nitrification commences from the very top of the filter in the presence of soluble BOD loadings previously thought to preclude the development of nitrifying biomass. Several reasons have been proposed to explain this, with the key argument being that the efficient oxygen transfer afforded by the media design is sufficient to satisfy heterotroph and autotroph oxygen demand simultaneously.     

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.     

Experimental simulation of biodegradation in rivers: Oxygen, organic matter and biomass concentration changes

Dissolved oxygen (DO) and biochemical oxygen demand (BOD) concentration changes after an organic matter discharge into a river have been studied in the absence of oxygen transfer. According to these laboratory experiments, biodegradation of various organic compounds (glucose, glutamic acid, starch, ovalbumin and ethanol) in Seine river samples incubated at 15 30°C follow a biphasic behaviour. During a lag-phase of 10–20 h, DO decreases linearly (0.12 ppm h⁻¹ at 20°C), whereas BOD is constant. During a subsequent aerobic exponential phase, DO and BOD uptake are proportional and increase exponentially with time (0.13 h⁻¹ at 20°C). Using cell ATP as biomass indicator, the latter phase was shown to correspond to a cell division step. A kinetic model was developed for stimulating DO and BOD concentration changes after a waste water discharge at temperatures ranging between 15 and 30°C.     

An interlaboratory study of dissolved oxygen in water

Dissolved oxygen concentrations in water samples free from chemical reductants may be stabilised by the addition of mercuric chloride (40 g m⁻³) and storage in gas-tight bottles. This preservation technique has been used in an interlaboratory study of dissolved oxygen analysis in New Zealand laboratories. At reference concentrations of 1.20 and 5.86 g m⁻³, there was a significant positive bias in results reported for both the Winkler method (0.24 and 0.22 g m⁻³ respectively) and the membrane electrode method (0.59 and 0.62 g m⁻³ respectively). Inadequate precautions to avoid sample aeration during handling and analysis probably caused the bias.     

Biological denitrification in an upflow sludge blanket reactor

A study was made of a denitrifying sludge blanket reactor without carrier material for the activated sludge. The reactor was fed with a solution of alcoholic waste and sodium nitrate. The highest surface load in our study was 2 m h^?1 and the sludge concentration in the sludge blanket at this flow was in the range of 40 g TS l^?1. To our opinion higher surface loads are attainable. The nitrate removal rate that at least can be obtained is 500 g NO^?₃ ? N m^?3 h^?1.     

Anaerobic treatment kinetics of palm oil sludge

Treatment of palm oil sludge using the completely-mixed, suspended growth, continuous anaerobic fermentation system was studied in a laboratory scale. Biokinetic coefficients for system with and without solids recycle were evaluated. The treatment systems were effective in the removal of BOD, COD, and volatile suspended solids. The gas production rate averaged around 0.91 g⁻¹ BOD utilized with an energy yield of 20,000 J g⁻¹ BOD utilized for units with _c greater than 25 days. The _c^m, minimum solids retention time, was calculated to be more than 10 days. Measured _c^m was, however, lower than 7 days.     

Oxygenation par le peroxyde d'hydrogene des biomasses fixees utilisees en traitement biologique des eauxOxygenation by hydrogen peroxide of the fixed biomass used in biological water treatment

Because of their advantages as compared to flocculated biomass processes, there is now a revival of interest in fixed biomass processes:no mishaps due to bad flocculation, particularly with filamentous organisms (bulking)compact equipment owing to the ability to obtain greater biomass concentrations (several g l^?1), which is impossible in flocculated biomass.In this paper, we will consider mainly bio-discs and submerged fixed bed filters. In bio-disc investigations, Hoehn and Ray's (1973), Kornegay and Andrew's (1968) now classical results showed that the bacterial film only acts on the surface, over a thickness which, at best, does not exceed 150 μm. At the same time, Bungay's (1969) very accurate measurements showed that the film active thickness coincides with the depth where the oxygen concentration in the film is higher than the critical oxygen concentration. In submerged filters, Elmaleh (1976) and Grasmick's (1978) theoretical studies permit one to define a Useful Column Height (UCH) which corresponds to the active part of the reactor and which is superposed on the height where oxygen concentration is higher than the critical oxygen concentration. In classical devices, the UCH is relatively low: approx. 0.50-1 m. In both cases, the system is provided with oxygen through an exchange between the air and the effluent to be treated, at a gas-liquid interface. This procedure limits the O₂ concentration to about 9 mg O₂ l^?1, at the ambient temperature. Therefore, to increase the UCH of a submerged reactor or the active thickness of a bio-disc film by increasing the oxygen penetrating depth, the oxygen partial pressure in the gas phase should be increased by either using pure oxygen or increasing total gas phase pressure.These two methods are somewhat difficult to use and we prefer to use another method: bringing dissolved oxygen directly into the liquid phase without the exchange at the gas-liquid interface. This is feasible by using an oxygen liberating labile chemical reagent i.e. hydrogen peroxide. We consider two types of fixed biomasses: the bio-discs and the submerged filters.Bio-discs. The apparatus used is shown in Fig. 1. The utilization of H₂O₂ resulted in a very sharp increase in the substrate removal efficiency. It is observed that the substrate removal efficiency (Figs 5 and 6) and the reduced pollution flux (Figs 4 and 7) show a maximum when these are plotted as a function of the ratio: equivalent quantity of O₂ given by H₂O₂/O₂ demanded by the effluent and as a function of dissolved oxygen in the liquid phase. Moreover, these curves suggest that oxygen acts as an inhibitor and different attempts at modeling, based on standard models of inhibiting effects, lead to the exponential model giving the lowest deviation (Fig. 8).Submerged packed reactors. The apparatus used is shown in Fig. 3. This unit is fed by urban effluents and the oxygenation in the reactor is carried out by using diluted H₂O₂ (0.5-1.5 N).     

Effect of loading rate and oxygen supply on nitrification in a non-porous membrane biofilm reactor

A nitrifying membrane biofilm reactor (MBfR) was operated over 170 days, to assess the effect of ammonia loading rate under O₂-excess conditions, and the effect of dissolved oxygen under O₂-limiting conditions on nitrification efficiency. The MBfR was fed pure oxygen by diffusion through a non-porous membrane. Five different loading rates, ranging from 1.92 to 5.53 g N/m² d, were tested, yielding specific nitrification rates (SNR) ranging from 1.54 to 2.60 g N/m² d. SNR increased linearly with specific loading rate, up to the load of 3.5 g N/m² d, which indicated that mass transfer was linearly related to the bulk ammonia concentration. Beyond that load, substrate diffusion limitation inhibited further increase of SNR. When operating the system under limited oxygen supply conditions, 100% oxygen utilization was achievable. Maintenance of higher oxygen supply allowed a slightly higher SNR due to the growth of nitrifiers at the outer side of the biofilm (away from the membrane surface). Nitrification batch tests confirmed that the fraction of nitrifiers in the solids detached from the surface of the biofilm (and washed out with the effluent), was twice as high during oxygen-excess conditions when compared to oxygen-limiting conditions.     

Effect of oxygen concentration on the rates of denitratification and denitrification in the sediments of an eutrophic lake

The effect of oxygen concentration on the rates of denitratification and denitritification was investigated by the acetylene inhibition method during initial 1-h incubation period after preculture under complete anaerobic conditions for wide ranges of nitrate and nitrite concentrations using sediment sample collected from a highly eutrophic lake. A maximum denitratification rate of 4 μmol (g-dry mud)^?1 h^?1 was obtained under anaerobic conditions. The denitratification rate was found to be a decreasing function of the oxygen concentration below 60 μM. Approximately the same rate was observed for denitritification in the range below 30 μM O₂. Beyond 30 μM O₂, this rate dropped to the half of the maximum, and remained almost constant until a critical oxygen concentration was attained. The critical concentration, above which denitritification was suppressed thoroughly, depended on nitrite concentration.     

Oxygen uptake of bottom sediments studied in situ and in the laboratory

Oxygen uptake by soft bottom sediments was measured in situ with an oxygen electrode in a bell jar. Values in the range 0·3-3·0 g O₂ m⁻² d⁻¹ were obtained at 19 localities in fresh and brackish water. Comparative measurements were made in the laboratory on sediment cores. These gave consistently lower values than the in situ measurements. Laboratory experiments showed that the oxygen uptake depended on the oxygen concentration and that the temperature coefficient decreased with increasing temperature. There was no simple correlation between oxygen uptake and content organic matter in sediments.