Scaling is an integral component of ecology and earth science. To date, the ability to determine the importance of air – water gas exchange across large spatial scales is hampered partly by our ability to scale the gas transfer velocity and stream hydraulics. Here we report on a metadata analysis of 563 direct gas tracer release experiments that examines scaling laws for the gas transfer velocity. We found that the gas transfer velocity scales with the product of stream slope and velocity, which is in alignment with theory on stream energy dissipation. In addition to providing equations that predict the gas transfer velocity based on stream hydraulics, we used our hydraulic data set to report a new set of hydraulic exponents and coefficients that allow the prediction of stream width, depth, and velocity based on discharge. Finally, we report a new table of gas Schmidt number dependencies to allow researchers to estimate a gas transfer velocity using our equation for many gasses of interest.

/pdf/scaling-the-gas-transfer-velocity-and-hydraulic-geometry-in-2byfxp1gu9.pdf

Scaling the gas transfer velocity and hydraulic geometry in streams and small rivers

Introduction to Water Quality and to Wastewater Treatment Basic Principles of Wastewater Treatment Natural Treatment Systems Anaerobic Reactors Activated Sludge Sludge Treatment and Disposal

Biological Wastewater Treatment in Warm Climate Regions

Whole-stream metabolism in a first-order stream was measured using upstream–downstream changes in dissolved oxygen (DO) concentration measured at 1-min intervals over a 40-h period. The measured ch...

Improvements to the diurnal upstream-downstream dissolved oxygen change technique for determining whole-stream metabolism in small streams

Experimental research and prediction of the effect of chemical and biogenic sulfuric acid on different types of commercially produced concrete sewer pipes

A review of dissolved oxygen modelling techniques for lowland rivers.

Information on the rate of absorption of oxygen in sewers is needed for calculations of biological oxidation in sewers and for an understanding of sulfide buildup in sewers. Published equations for stream aeration are at variance with one another, and in any case do not provide a basis for needed predictions of reaeration rates in sewers. Measurements of oxygen uptake were made in twelve functioning sewers. By viewing all of the data and prior mathematical treatments synoptically, a general predictive equation was devised. Reaeration rates for sewage streams can now be predicted with an expected standard error of ±10%. The general equation coefficient for predicting reaeration in streams of pure water is not yet known with similar accuracy, but could be determined by precision experiments. The rates in sewage streams are apparently about a third as great as in pure water.

Oxygen Absorption in Streams

SUMMARY A practical equation for forecasting sulfide buildup in partly filled sewers must be limited to the use of input information that is reasonably obtainable by measurement or estimation For this reason, it appears that forecasting will generally be limited by the assumption that certain unquantified variables, especially the dissolved oxygen content of the sewage stream, are in ranges favorable for sulfide buildup An equation constructed with this limitation gives results that are inherently conservative, but useful for engineering purposes Sulfide buildup rates will rarely exceed by any significant amount the rates calculated by the following equation: d [ S ] d t = 032 x 10 − 3 [ B O D ] ( 107 ) ( T − 20 ) − 064 ( s u ) 3 / 8 [ s ] d m − 1

The forecasting of sulfide build-up rates in sewers

Historically, Los Angeles County has learned to quench its thirst from many sources. Completion of the California Water Project in 1971-72 and the second barrel of the Owen River Aqueduct in 1972 will ensure adequate supplies until about 1990. These high quality imported waters will also enhance the quality of treated wastewater for subsequent reuse. Undoubtedly, much of this better quality water will be used directly for irrigation or percolation to the underground. New processes resulting from a rapidly developing technology can be readily integrated into the water renovation plants not being operated or under construction by the Sanitation Districts as new reuse applications arise. Ultimately, demineralization of wastewater may be practical on a large scale, since processes now under development appear competitive with alternative sources of supply. While a significant quantity of wastewater is suitable for treatment and reuse, it should be considered in its proper role—as a supplemental supply.

John D. Parkhurst

Papers

Oxygen Absorption in Streams

The forecasting of sulfide build-up rates in sewers

Wastewater Reuse—A Supplemental Supply