Evaluation of ground water denitrification at a biosolids disposal site

A study was conducted at a sanitary sewage sludge(biosolids) disposal site in Springfield, Illinois, U.S.A. todetermine if biological denitrification played a significantfactor in attenuation of ground water nitrate values. The siteselected for this study is a 23 ha (57 acre) dedicatedbiosolids disposal facility located adjacent to a 75.7 millionliter per day (20 million gallons per day) municipal treatmentplant that uses anaerobic solids stabilization for treatment ofgenerated biosolids material. Biosolids have been disposed of byfixed-point spray applicators at the site since 1976, which hascaused ground water nitrate levels to increase significantlyabove background levels. A method was developed using aconservative chemical tracer to simulate the biosolidsapplication process and monitor the ground water directly beneaththe simulated disposal site. Results demonstrated a net declineof nitrates that could not be attributed to dilution alone.While the monitoring methodology developed for this study didnot directly estimate the denitrification rate, a rate foroverall nitrate reduction was calculated that could be consideredto take into account all transport and reduction mechanisms suchas denitrification, advection, dispersion and dilution.     

OPTIMAL CONTROL OF RESERVOIR RELEASES TO MINIMIZE SEDIMENTATION IN RIVERS AND RESERVOIRS1

ABSTRACT: An optimal control methodology and computational model are developed to evaluate multi‐reservoir release schedules that minimize sediment scour and deposition in rivers and reservoirs. The sedimentation problem is formulated within a discrete‐time optimal control framework in which reservoir releases represent control variables and reservoir bed elevations, storage levels, and river bed elevations represent state variables. Constraints imposed on reservoir storage levels and releases are accommodated using a penalty function method. The optimal control model consists of two interfaced components: a one‐dimensional finite‐difference simulation module used to evaluate flow hydraulics and sediment transport dynamics, and a successive approximation linear quadratic regulator (SALQR) optimization algorithm used to update reservoir release policies and solve the augmented control problem. Hypothetical two‐reservoir and five‐reservoir networks are used to demonstrate the methodology and its capabilities, which is a vital phase towards the development of a more robust optimal control model and application to an existing multiple‐reservoir river network.