Spatial Variability of Anaerobic Processes and Wastewater pH in Force Mains.

The present study focuses on anaerobic organic matter transformation processes in force mains for the purpose of improving existing sewer process models. Wastewater samples were obtained at 100 m intervals from a 1 km long pilot scale force main and measured for several wastewater parameters. Transformation rates for selected parameters were calculated and their spatial variability analyzed.

Invertebrates in stormwater wet detention ponds - Sediment accumulation and bioaccumulation of heavy metals have no effect on biodiversity and community structure.

The invertebrate diversity in nine stormwater wet detention ponds (SWDP) was compared with the diversity in eleven small shallow lakes in the western part of Denmark. The SWDPs and lakes were chosen to reflect as large a gradient of pollutant loads and urbanization as possible. The invertebrates as well as the bottom sediments of the ponds and shallow lakes were analyzed for copper, iron, zinc, cadmium, chromium, lead, aluminum, nickel, arsenic and the potentially limiting nutrient, phosphorus.

Modeling Sulfides, pH and Hydrogen Sulfide Gas in the Sewers of San Francisco.

An extensive measuring campaign targeted on sewer odor problems was undertaken in San Francisco. It was assessed whether a conceptual sewer process model could reproduce the measured concentrations of total sulfide in the wastewater and H2S gas in the sewer atmosphere, and to which degree such simulations have potential for further improving odor and sulfide management. The campaign covered measurement of wastewater sulfide by grab sampling and diurnal sampling, and H2S gas in the sewer atmosphere was logged.

Modeling anaerobic organic matter transformations in the wastewater phase of sewer networks.

A conceptual model to simulate transformations of organic matter and sulfur compounds in the wastewater phase of sewer networks under anaerobic conditions was developed. For calibration and validation of the model, a series of laboratory experiments on generation of readily biodegradable organic matter and sulfide under anaerobic conditions in samples of wastewater was conducted. Compared with previous studies, the proposed model includes sulfate reduction in the bulk water as well as a revised description of fermentation processes.

Sorption media for stormwater treatment--a laboratory evaluation of five low-cost media for their ability to remove metals and phosphorus from artificial stormwater.

Five sorption materials were studied with a focus on polishing pretreated stormwater: crushed limestone, shell-sand, zeolite, and two granulates of olivine. These materials are commercially available at comparatively low cost and have been subjected to a minimum of modification from their natural states. The sorbents were tested for phosphorus, arsenic, cadmium, chromium, copper, nickel, lead, and zinc at concentration and conditions relevant for typical stormwater.

Effect of sewer headspace air-flow on hydrogen sulfide removal by corroding concrete surfaces.

Hydrogen sulfide adsorption and oxidation by corroding concrete surfaces at different air-flows were quantified using a pilot-scale sewer reactor. The setup was installed in an underground sewer research station with direct access to wastewater. Hydrogen sulfide gas was injected into the headspace of the sewer reactor once per hour in peak concentrations of approximately 500 ppmv.

Improved urban stormwater treatment and pollutant removal pathways in amended wet detention ponds.

Dissolved and colloidal bound pollutants are generally poorly removed from stormwater in wet detention ponds. These fractions are, however, the most bio-available, and therefore three wet detention ponds were amended with planted sand filters, sorption filters and addition of precipitation chemicals to enhance the removal of dissolved pollutants and pollutants associated with fine particles and colloids. The three systems treated runoff from industrial, residential and combined (residential and highway) catchments and had permanent volumes of 1,990, 6,900 and 2,680 m(3), respectively.

Anaerobic transformations of organic matter in collection systems.

Anaerobic transformations of wastewater organic matter in the bulk water phase of collection system networks were investigated in laboratory-scale experiments. The wastewater was collected from three locations, which provided samples with different characteristics, ranging from young to mature. Hydrolysis, fermentation, and sulfate reduction were identified as the most important anaerobic processes.

Growth kinetics of hydrogen sulfide oxidizing bacteria in corroded concrete from sewers.

Hydrogen sulfide oxidation by microbes present on concrete surfaces of sewer pipes is a key process in sewer corrosion. The growth of aerobic sulfur oxidizing bacteria from corroded concrete surfaces was studied in a batch reactor. Samples of corrosion products, containing sulfur oxidizing bacteria, were suspended in aqueous solution at pH similar to that of corroded concrete.

Modeling of hydrogen sulfide oxidation in concrete corrosion products from sewer pipes.

Abiotic and biotic oxidation of hydrogen sulfide related to concrete corrosion was studied in corrosion products originating from a sewer manhole. The concrete corrosion products were suspended in an acidic solution, mimicking the conditions in the pore water of corroded concrete. The removal of hydrogen sulfide and dissolved oxygen was measured in parallel in the suspension, upon which the suspension was sterilized and the measurement repeated.

Biodegradability of organic matter associated with sewer sediments during first flush.

The high pollution load in wastewater at the beginning of a rain event is commonly known to originate from the erosion of sewer sediments due to the increased flow rate under storm weather conditions. It is essential to characterize the biodegradability of organic matter during a storm event in order to quantify the effect it can have further downstream to the receiving water via discharges from Combined Sewer Overflow (CSO). The approach is to characterize the pollutograph during first flush.

Influence of pipe material and surfaces on sulfide related odor and corrosion in sewers.

Hydrogen sulfide oxidation on sewer pipe surfaces was investigated in a pilot scale experimental setup. The experiments were aimed at replicating conditions in a gravity sewer located immediately downstream of a force main where sulfide related concrete corrosion and odor is often observed. During the experiments, hydrogen sulfide gas was injected intermittently into the headspace of partially filled concrete and plastic (PVC and HDPE) sewer pipes in concentrations of approximately 1,000 ppm(v).

Effects of pH and iron concentrations on sulfide precipitation in wastewater collection systems.

Sulfide precipitation by addition of iron salts is a widely used strategy for sulfide control in wastewater collection systems. Several parameters, such as pH, oxidation-reduction conditions, and reactant concentrations, are known to affect the feasibility of the method. However, their combined effects are difficult to predict for complex media, such as wastewater.

Modeling the formation and fate of odorous substances in collection systems.

A conceptual model that simulates the formation and fate of odorous substances in branched collection systems is presented. The model predicts the activity of the relevant biomass phenotypes under aerobic, anoxic, and anaerobic conditions in force mains and gravity sewers. The formation and fate of individual, malodorous substances in the bulk water, biofilms, and sediments are modeled.

Corrosion of concrete sewers--the kinetics of hydrogen sulfide oxidation.

Hydrogen sulfide absorption and oxidation by corroding concrete surfaces was quantified in a test rig consisting of 6 concrete pipes operated under sewer conditions. The test rig was placed in an underground sewer monitoring station with access to fresh wastewater. Hydrogen sulfide gas was injected into the pipe every 2nd hour to peak concentrations around 1000 ppm.

Aerobic and anaerobic transformations of sulfide in a sewer system--field study and model simulations.

The formation and fate of sulfide in a force main and a downstream-located gravity sewer were investigated in an extensive field study. Sulfide formation in the force main was significant. However, during 14 minutes of transport in the gravity sewer, the sulfide concentration decreased 30%, on average.

Kinetics and stoichiometry of aerobic sulfide oxidation in wastewater from sewers-effects of pH and temperature.

Kinetics and stoichiometry of aerobic chemical and biological sulfide oxidation in wastewater from sewer networks were studied. In this respect, the effects of temperature and pH were investigated in the ranges 10 to 20 degrees C and 5 to 9, respectively. The temperature dependency of sulfide oxidation kinetics was described using an Arrhenius relationship.

Kinetics and stoichiometry of sulfide oxidation by sewer biofilms.

Oxidation of sulfide under aerobic conditions by biofilms grown on municipal wastewater in 6 identical pipe reactors was investigated. The biofilms were grown at pH 7.6 and temperatures of 20 and 25 degrees C under aerobic-anaerobic transient conditions with pulse dosing of sulfide in the bulk water.

Stochastic modeling of chemical oxygen demand transformations in gravity sewers.

Wastewater quality characteristics in terms of biomass, its substrates, and the corresponding kinetic and stoichiometric parameters were determined based on 109 wastewater samples originating from five different campaigns in four different sewer networks. Quality parameters were determined by model calibration of measured wastewater oxygen uptake rates applying a model that describes the aerobic breakdown of wastewater organic matter. Thereafter, the distributions of the parameters were analyzed.

Sulfide-iron interactions in domestic wastewater from a gravity sewer.

Interactions between iron and sulfide in domestic wastewater from a gravity sewer were investigated with particular emphasis on redox cycling of iron and iron sulfide formation. The concentration ranges of iron and total sulfide in the experiments were 0.4-5.

Sustainable stormwater management at Fornebu--from an airport to an industrial and residential area of the city of Oslo, Norway.

The Oslo Airport at Fornebu was closed in 1998 after 60 years of operation. An area of 3.1 km(2) was made available for one of Norway's biggest property development projects.

Air-water transfer of hydrogen sulfide: an approach for application in sewer networks.

The emissions process of hydrogen sulfide was studied to quantify air-water transfer of hydrogen sulfide in sewer networks. Hydrogen sulfide transfer across the air-water interface was investigated at different turbulence levels (expressed in terms of the Froude number) and pH using batch experiments. By means of the overall mass-transfer coefficient (KLa), the transfer coefficient of hydrogen sulfide (KLa(H2S)), referring to total sulfide, was correlated to that of oxygen (KLa(O2)) (i.

Determination of kinetics and stoichiometry of chemical sulfide oxidation in wastewater of sewer networks.

A method for determination of kinetics and stoichiometry of chemical sulfide oxidation by dissolved oxygen (DO) in wastewater is presented. The method was particularly developed to investigate chemical sulfide oxidation in wastewater of sewer networks at low DO concentrations. The method is based on continuous measurement of the reactants allowing the kinetics to be determined at varying reactant concentrations during the course of the experiment.