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.     

Modifications to electrolytic respirometer systems for precise determination of BOD exertion kinetics in receiving waters

Modifications to an electrolytic respirometric system are described which facilitate precise measurements of BOD progressions for low substrate concentration (BOD₅ < 20 g m^?3) as found in natural waters receiving organic enrichment. Samples may be incubated at any desired temperature or dissolved oxygen concentration with automatic hourly monitoring of the BOD progression. Subsamples may be withdrawn at any time without interference to the measurement. The system is independent of atmospheric temperature and pressure fluctuations and has a detection sensitivity of 0.05 mg of oxygen. Nomographs are presented to enable the maximum dissolved oxygen deficit, and the “apparent lag” time to be estimated. CO₂ removal, which may result in an extended lag phase, need not be used for BOD values below 50 g m^?3 provided adequate buffering is supplied.     

Ecological equilibrium on biological activated carbon

This paper examines the potential of a biological activity control system (BACS) for biological activated carbon (BAC) in comparison to granular activated carbon (GAC) for the treatment of potable water. The overall objective of the project is to produce drinking water of a higher quality more economically by developing a BACS for exhausted GAC that can be transformed to BAC by the development of a natural biofilm during the bio-regeneration mode. The research therefore may be interesting for water companies and the activated carbon industry. Findings show that the lifetime of a GAC filter can be significantly extended by maintaining an active biofilm that has to be controlled in order to avoid filter clogging. The most important parameters are dissolved oxygen (DO), pH and a correct balance of nutrients, which enables a natural control of the biomass. pH control was required to maintain an optimal bacteria-protozoa level. Excessive growth of filamentous bacteria can be prevented by a decrease in DO, increase in pH and the reduction of one essential nutrient, e.g. total phosphorus (P). Total organic carbon (TOC) and chemical oxygen demand (COD) values were reduced by bioactivity. DO, turbidity and suspended solids (SS) values were kept in acceptable ranges with respect to drinking water objectives. Plants without a significant population of protozoa deliver turbid low quality effluent high on SS and biochemical oxygen demand (BOD). It was possible to control the biofilm on GAC containing a natural biofilm and BAC during the bio-regeneration mode. Natural and artificial bio-regeneration lead to similar performance characteristics.     

Water quality and pollution loading of a river segment affected by landfill leachate and domestic waste

The Marikina River in the Philippines has been polluted by Payatas landfill leachate, and domestic and agricultural waste. This study monitored the water quality at five stations on the river and two stations on two creeks that discharge to the river to determine the effects of Payatas landfill and to estimate pollution loading. The dissolved oxygen (DO), chemical oxygen demand (COD) and other water quality parameters were compared with the Philippines Standards for river water classification. It was found that Payatas leachate has a significant influence on the DO and COD levels as well as other water quality parameters. Per capita pollution loading for Quezon City was found to be lower than for Europe and Japan. The effect of leachate is more significant during the dry season. It is recommended that a leachate collection system be established to prevent leachate form entering Payatas creek, and that the Patayas landfill be replaced with a modern landfill site, conforming to current best practice at another location.

List of Abbreviation: BOD= Biological Oxygen Demand COD = Chemical Oxygen Demand DO = Dissolved Oxygen EC = Electrical Conductivity M1, M2, M3, M4, M5 = monitoring stations TDS = Total Dissolved Solids TSS = Total Suspended Solids     

Potential of using nonwoven polyester fabric (NWPF) as a packing media in multistage passively aerated biological filter for municipal wastewater treatment

The performance of a multistage passively aerated biological filter (PABF) packed with Nonwoven polyester fabric (NWPF) for municipal wastewater treatment was investigated under different operating conditions. The system was operated at different hydraulic retention times (HRTs) of 2.3, 1.72 and 1.38 h and corresponding to organic loading rates (OLRs) of 1.77, 2.15 and 2.9 kg BOD/m³. d. Increasing HRT and decreasing OLR, increased dissolved oxygen (DO) and consequently increased the removal rate of organic matters (87%), suspended solids (95.8%) and ammonia (88%). Profile results from different compartments showed that the major part of organic and suspended matters was removed in the upper layers of the system, whereas most of the suspended solids were trapped, while the nitrification process took place in the lower part of the PABF system because of the increase in DO concentrations. The results proved the advantage of using NWPF. It has pleated and rough surface which retain more biomass compared with plain surface. Excess biomass produced from PABF was negligible compared to conventional treatment systems.     

Management of optimum water quality in a stream

An optimal waste discharge policy along a stream is investigated based on a program of minimizing the total cost benefit function on a regional basis. The system consists of a stream along which are located several inputs of waste and intakes of water. The cost benefit function comprises of the sum of the cost of waste treatment and the cost of water treatment minus the benefits derived from maintaining a certain water quality in the stream. The biochemical oxygen demand and the dissolved oxygen are considered to be the primary indicators of water quality. A steady state dispersion model is employed to predict the BOD and DO concentrations along the stream.     

Direct measurement of oxygen in river substrates

A study was conducted to establish if river substratum dissolved oxygen (DO) could be measured directly. Hitherto, such measurements have been carried out by proxy and indirect methods or by direct methods following installation of cores/tubes into the streambed. Redox potential (Eh) readings were also taken at most of the sites for comparison. The overall conclusion is that a reliable, off‐the‐shelf instrumental method of directly measuring DO in river substrates has been tested in laboratory and field conditions. The Eh meter, per contra, did give aberrant results for some measurements particularly in the field but had the advantage of a slimmer probe for easier penetration into substrata. The measurement technique, to determine river interstitial sediment O₂, is a simple and quick direct in situ method that produces reliable results.     

Deoxygenation in a mobile-bed river—II. Model calibration and post-audit

Benthic metabolism accounts for over 90% of oxygen uptake in the Tarawera, a mobile-bed river receiving treated pulp mill effluent. A steady-state DO model was developed in 1984 which uses zero-order kinetics for benthic metabolism. During calibration a strong linear relationship was identified between the river deoxygenation rate (benthic oxygen uptake rate) and the river BOD concentration just below the main outfall. When tested against non-steady monitoring data the model successfully predicted monthly-average DO concentrations but tended to “overshoot” when waste loads varied. This suggests that the mobile-bed communities have some ability to attenuate the effects of varying waste loads. A post-audit of the model using recent monitoring data shows that the model can predict day-to-day variations of DO under average waste loading conditions but not when there are sudden large changes of waste load. It can be inferred that there are two different time scales operating: surface microbial communities respond quickly (1–2 days) to variations in waste load, but following a major reduction in waste load, reworking of deeper sediments depresses river DO for several weeks. There is a need to develop “biofilm” type models of mobile-bed rivers in order to refine predictions of DO under non-steady waste loadings.     

An improved system for the control of dissolved oxygen in freshwater aquaria

A system for the removal and control of dissolved oxygen (DO) from freshwater was designed and constructed with aquarium-type fish studies in mind. Degassed water was obtained using a partial vacuum of −14 psi, and DO regulated at an aquarium scale using electronically controlled aeration with timed partial water renewal. The degassing system was capable of producing water with ∼1.7 mg L⁻¹ DO within 10 min of operation, and 0.55 mg L⁻¹ after 2 h. The control system was capable of maintaining DO levels of ca 0.8 mg L⁻¹ over 48 h in the absence of aeration and further capable of precisely controlling DO levels as low as 1.16±0.002 mg L⁻¹ (mean±SEM) with aeration over a 48 h period.     

Environmental risk of dissolved oxygen depletion of diverted flood waters in river polder systems - A quasi-2D flood modelling approach

River polders are retention basins contained by levees alongside rivers into which water from the main river channel is diverted during extreme floods in order to cap the peak discharge of the flood hydrograph and to alleviate downstream flood risk by reducing the water levels. The retained water, however, is stagnant and the organic material in the water and the bottom sediments imposes a strong oxygen demand on the water. This paper presents a quasi two-dimensional computer-based methodology to assess the environmental risk exhibited by the operation of polders with which the concentration of dissolved oxygen in river and polder water can be simulated. A Monte-Carlo analysis allows the probability distribution of all the outcomes of the minimum dissolved oxygen levels in the water to be derived. From this analysis, the environmental risk of the dissolved oxygen concentrations in the polder water falling below 2 mg O₂/L (the level considered critical for aquatic ecosystems) can be determined.The August 2002 extreme flood event on the Elbe River, Germany, with a proposed polder system variant was used to calibrate the model. A daily time step was used to for the simulations for a time frame 12-21 August 2008. The results show plausible spatial and temporal variations in the dissolved oxygen concentrations within the polders. The quasi-2D approach was successful in simulating the spatial distribution of water quality constituents in the polder system. There is up to approximately 20% risk that dissolved oxygen levels fall below 2 mg/L in the polders. This risk can potentially increase if sediment oxygen demand increases due to crop residue and water temperatures in polders increase. High nutrient transport in the river during flooding can cause a spurt of phytoplankton growth in the polders.     

Organic matter transport and degradation in the river Seine (France) after a combined sewer overflow

The impact of a combined sewer overflow (CSO) upon receiving waters has been studied in the river Seine during Summers 1995 and 1996. Three main events have been monitored with special attention paid to the computation of oxygen, carbon and suspended solids budgets. Bacterial biomass and bacterial production rates have been measured to provide a more accurate understanding of the carbon cycle of the river Seine. Oxygen consumption inside the polluted water masses was totally due to the activity of large bacteria discharged into the river by the CSO, the activity of native small bacteria did not significantly increase after CSOs. Suspended solids issued from the CSO very quickly settles in this deep, slowly flowing river. However, discharged dissolved organic carbon (DOC) cannot account for the observed oxygen depletions, the additional carbon source could be phytoplankton or deflocculated/degraded particulate organic matter.     

Using river distances in the space/time estimation of dissolved oxygen along two impaired river networks in New Jersey

Understanding surface water quality is a critical step towards protecting human health and ecological stability. Because of resource deficiencies and the large number of river miles needing assessment, there is a need for a methodology that can accurately depict river water quality where data do not exist. The objective of this research is to implement a methodology that incorporates a river metric into the space/time analysis of dissolved oxygen data for two impaired river basins. An efficient algorithm is developed to calculate river distances within the BMElib statistical package for space/time geostatistics. We find that using a river distance in a space/time context leads to an appreciable 10% reduction in the overall estimation error, and results in maps of DO that are more realistic than those obtained using a Euclidean distance. As a result river distance is used in the subsequent non-attainment assessment of DO for two impaired river basins in New Jersey.     

Sedimentary microbial oxygen demand for laminar flow over a sediment bed of finite length

Dead organic material accumulated on the bed of a lake, reservoir or wetland often provides the substrate for substantial microbial activity as well as chemical processes that withdraw dissolved oxygen (DO) from the water column. A model to estimate the actual DO profile and the "sedimentary oxygen demand (SOD)" must specify the rate of microbial or chemical activity in the sediment as well as the diffusive supply of DO from the water column through the diffusive boundary layer into the sediment. Most previous experimental and field studies have considered this problem with the assumptions that the diffusive boundary layer is (a) turbulent and (b) fully developed. These assumptions require that (a) the flow velocity above the sediment bed is fast enough to produce turbulent mixing in the boundary layer, and (b) the sediment bed is long. In this paper a model for laminar flow and SOD over a sediment bed of finite length is presented and the results are compared with those for turbulent flow. Laminar flow near a sediment bed is encountered in quiescent water bodies such as lakes, reservoirs, river backwaters, wetlands and ponds under calm wind conditions. The diffusive oxygen transfer through the laminar diffusive boundary layer above the sediment surface can restrict the microbial or chemical oxygen uptake inside the sediment significantly. The developing laminar diffusive boundary layer above the sediment/water interface is modeled based on the analogy with heat transfer, and DO uptake inside the sediment is modeled by Michaelis-Menten microbial growth kinetics. The model predicts that the rate of SOD at the beginning of the reactive sediment bed is solely dependent on microbial density in the sediment regardless of flow velocity and type. The rate of SOD, and the DO penetration depth into the sediment decrease in stream-wise direction over the length of the sediment bed, as the diffusive boundary layer above the sediment/water interface thickens. With increasing length of the sediment bed both SOD rate and DO penetration depth into the sediment tend towards zero if the flow is laminar, but tend towards a finite value if the flow is turbulent. That value can be determined as a function of both flow velocity and microbial density. The effect of the developing laminar boundary layer on SOD is strongest at the very lowest flow velocity and/or highest microbial density inside the sediment. Under quiescent conditions, the effective SOD exerted by a reactive sediment bed of a lake or wetland approaches zero, i.e. no or very little oxygen demand is exerted on the overlying water column, except at the leading edge.     

低溶解氧对生物膜特性的影响研究

通过考察生物膜的生长特性、除污效率、脱氢酶活性以及微生物群落组成,分析了低溶解氧对生物膜特性的影响,验证了在低溶解氧条件下采用生物膜反应器处理低浓度生活污水的可行性.试验发现,在低溶解氧条件下生物膜具有特殊的生长特性与外观结构,对COD、SS的去除率分别达到60%和90%以上;由于液相中的低浓度有机物向生物膜内的扩散通量较小,使其成为生物膜降解活性的主要限制因素;长期在低溶解氧下运行会使生物膜内环境更适合兼性异养菌的生长,而总的细菌含量变化不大,保证了生物膜具有较高的处理效率.这为降低污水处理能耗,拓宽生物膜反应器的应用范围提供了新的思路和理论基础.     

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.     

Measurement of sediment oxygen demand for modelling dissolved oxygen distribution in tidal Keelung River

The Keelung River is one of the major branches of the Danshuei River estuarine system, which runs the metropolitan capital city of Taipei, Taiwan, and receives a large of amount of wastewater. The dissolved oxygen (DO) concentration is generally low in the tidal portion of the Keelung River. Hypoxia/anoxia occurs often, particularly during a low-flow period. The sediment oxygen demand (SOD) amounts to a significant value, hence increasing the total oxygen demand load of the river. The present work reports on laboratory SOD made on grab sediment core samples in situ that are undisturbed. The results reveal that SOD values fluctuate with variations in seasons and are higher in summer due to a high-temperature effect. It was found in the laboratory tests that the average SOD (at 20 °C) value is 0.76 g/m²/day and the maximum SOD (at 20 °C) value reaches 1.58 g/m²/day. The mean values of measured SOD at each station were adopted in the vertical two-dimensional water quality model to simulate the DO distribution along the tidal Keelung River. The simulated results are in reasonable agreement with the measured DO distribution in the river. Model sensitivity analyses were also conducted with increasing and decreasing SOD. It reveals that SOD is an important parameter that affects the DO distribution in the tidal estuary.     

Impact of the Budha Nallah brook on the river Satluj waters. i—some physico‐chemical parameters

The impact of grossly polluted waters of the Budha Nallah on the water quality in the realm of physico‐chemical characteristics of the river Satluj after its confluence with the river was studied. The analysis of water at downstream spot (3 km after the point of confluence of Budha Nallah) revealed a significant increase in the levels of free‐CO₂, alkalinity, chlorides, total hardness, sulphates, water soluble phosphates, nitrates, ammonia, suspended solids, biochemical oxygen demand (BOD) and the chemical oxygen demand (COD), whereas levels of dissolved oxygen and pH declined when compared with the water quality at the upstream spot (3 km before the point of confluence of Budha Nallah).     

A dynamic model for DO—BOD relationships in a non-tidal stream

Dynamic models for dissolved oxygen (DO)-biochemical oxygen demand (BOD) interaction in a reach of river are not easily verified owing to the difficulties in obtaining data. In this paper a simple lumped-parameter model is presented and verified by deterministic simulation against field measurements collected over an 80-day period from the River Cam in eastern England. An important feature of the model is a pseudo-empirical term based on sunlight hours which is introduced to predict explicitly the significant effects of algal growth and decay encountered during prolonged sunny, dry weather.     

Spatial analysis of water quality trends in the Han River basin, South Korea

Spatial patterns of water quality trends for 118 sites in the Han River basin of South Korea were examined for eight parameters-temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), suspended sediment (SS), total phosphorus (TP), and total nitrogen (TN). A non-parametric seasonal Mann-Kendall's test determined the significance of trends for each parameter for each site between 1993 and 2002. There are no significant trends in temperature, but TN concentrations increased for the majority of the monitoring stations. DO, BOD, COD, pH, SS, and TP show increasing or decreasing trends with approximately half of the stations exhibiting no trends. Urban land cover is positively associated with increases in water pollution and included as an important explanatory variable for the variations in all water quality parameters except pH. Topography and soil factors further explain the spatial variations in pH, COD, BOD, and SS. BOD, COD, SS, and TP variations are consistently better explained by 100m buffer scale analysis, but DO are better explained by the whole basin scale analysis. Local water quality management or geology could further explain some variations of water quality. Non-point-source pollution exhibits strong positive spatial autocorrelation as measured by Moran's I, indicating that the incorporation of spatial dimensions into water quality assessment enhances our understanding of spatial patterns of water quality. The spatial regression models, compared to ordinary least square (OLS) models, always better explain the variations in water quality. This study suggests that spatial analysis of watershed data at different scales should be a vital part of identifying the fundamental spatio-temporal distribution of water quality.     

Unsteady diffusional mass transfer at the sediment/water interface: Theory and significance for SOD measurement

Dissolved oxygen uptake at a sediment/water interface (SOD) is controlled by mass transport and/or biochemical reactions in two adjacent boundary layers: the diffusive boundary layer delta(D) in the water and the penetration depth delta in the sediment. Either one of those boundary layers or both can be controlling. The transition from sediment control to water control is a function of shear velocity at the sediment/water interface (U(*)) and biochemical activity rate (micro(0)) in the sediment. A model was developed for the unsteady response of SOD and DO profiles near the sediment/water interface. Michaelis-Menten kinetics were used initially, but zero order kinetics work just as well when the half saturation coefficient K(O(2)) is small as was suggested by field data. Beginning with zero DO in the sediments the times required to reach steady state DO profiles and SOD was on the order of minutes to hours, faster where biochemical activity is strong. The values of SOD estimated by the model were compared with experimental data to verify the reliability of the model. The model can reproduce observed penetration depths and diffusive boundary layer thickness. Values of SOD estimated by the model were of same magnitude as observed data. The unsteady DO uptake model can be used to provide guidance for field measurements of SOD. Placing a chamber (with a stirrer) into the sediments disturbs the DO equilibrium at the sediment/water interface. A new equilibrium will be reached within a time that can be measured in terms of cumulative DO consumption in the chamber (SOD exerted). Upper bounds for (SOD exerted) are larger when biochemical activity in the sediments is smaller. Values of SOD exerted are less than 0.1gm(-2) when micro(0) is less than 50mgl(-1)d(-1) and U(*)>0.1cm/s. In other words, steady state conditions are easier to reach for high SOD values. Actual times required to reach steady state can be from minutes to hours. If flow conditions in the chamber and at the natural sediment/water interface are much different, measured SOD values have to be adjusted. A procedure for the adjustments, which can be substantial, has been developed.