School of Mechanical Engineering Seminar
Monday, April 9, 2018 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Biological NO₃^- Elimination from Reverse Osmosis Brackish Water Concentrate

Galit Sasson

Student of Prof. Hadas Mamane

Granot reverse osmosis (RO) desalination plant was established as part of the coastal aquifer rehabilitation project. This project aims to remove a natural salinity stain in the aquifer, comprising of chlorides and nitrates, by continuously pumping the saline water. The pumped brackish water is desalinated at Granot resulting in two streams: potable water and concentrated brine. One of the challenges of inland desalination is the terminal solution for brine disposal. At Granot plant the brine is discharged to the sea via a 30 km pipe line. According to Israel oceanographic & limnological research, the disposal of nitrogen rich brine into the Mediterranean Sea shore line, might cause several problems to marine life and sea ecosystem. Therefore, nitrate should be eliminated from the brine before sea disposal. There are many methods to eliminate nitrate but only few remove it terminally. One of these methods is heterotrophic denitrification, a bacterial process done at anoxic condition with an additional carbon source and nitrate as the electron acceptor. Completion of this process results in nitrate transforming to atmospheric nitrogen gas, leaving the treated water. This research is a pilot study aimed to examine the feasibility of denitrification on continuously working Granot RO brine and evaluate process performance and tolerance to possible inhibitors and planned interventions. Six distinctive process performance scenarios were observed throughout the pilot among them, half showed good process performance with complete nitrate and nitrite removal. At the three bad scenarios, complete nitrate removal was depicted yet, nitrite was present at the effluent. All the scenarios ran at lower carbon source (acetic acid) to nitrate ratio (2.1 -2.5 g Ac /g NO₃-N) than the theoretical value (3.5 g Ac /g NO₃-N). Better denitrification was observed at the higher range of the C:N ratio. Process showed endurance to shutdowns in the RO plant by relatively quick acclimation after reoperation. A sudden slight increase in salinity caused a process deterioration which resolved after the bacteria were acclimated. Dissolved oxygen (DO) concentration above 0.2 g/m³, documented as an inhibition limit, did not shift process from completion. Heterotrophic denitrification was found to be a possible alternative for nitrate elimination from the brine stream.   

School of Mechanical Engineering Semin

Monday, March 12, 2018 at 14:00
Wolfson Building of Mechanical Engineering, Room 206

Transport in Streams and Rivers (Tubes and canoes, rafts and kayaks, barges and paddle-wheels; so many ways to travel downstream.)

Diogo Bolster

Associate Professor and Frank M. Freimann Collegiate Chair in Hydrology

Department of Civil & Environmental Engineering & Earth Sciences

College of Engineering, University of Notre Dame

Rivers and streams transport the products of erosion and weathering, as well as anthropogenic materials collected from industrial, agricultural, and urban environments. While waterways are efficient transport networks, they are also important biogeochemical hotspots. Microbial biofilms colonizing organic and inorganic substrates at the sediment-water interface drive important biogeochemical reactions. The hyporheos is so efficient at cleaning up systems this that it is often referred to as a river’s liver, but the water flow there is orders of magnitude slower than in the main water channel while reaction rates are orders of magnitude greater. In brief, streams are complex heterogeneous systems characterized by a broad distribution of spatial and temporal transport scales influenced by water column and adjacent subsurface properties. This broad separation of scales leads to systems that are difficult to model mathematically, particularly over relevant scales of practical interest. Conventional modeling approaches simply fail and transport in streams and rivers is commonly observed to be “anomalous”. Here we present the results from a series of field experiments and high resolution numerical experiments of flow and conservative tracer transport that explore the characteristics of stream and hyporheic flow that control anomalous behaviors. We present a stochastic model with which we can model the observations and with which we can parse out individual mechanisms controlling large scale transport more clearly, enabling us to move towards building predictive mechanistic large scale models. We conclude with preliminary results and a discussion on what the implications for transport of more complex substances of interest might be, including nutrients and other biological matter, such as DNA.