Soil Aquifer Treatment System Research Articles

Techno-economic evaluation of soil-aquifer treatment using primary effluent at Ahmedabad, India

A pilot study was carried out in Sabarmati River bed at Ahmedabad, India for renovation of primary treated municipal wastewater through soil aquifer treatment (SAT) system. The infrastructure for the pilot SAT system comprised of two primary settling basins, two infiltration basins and two production wells located in the centre of infiltration basins for pumping out renovated wastewater. The performance data indicated that SAT has a very good potential for removal of organic pollutants, nutrients as well as bacteria and viruses. The SAT system was found to be more efficient and economical than the conventional wastewater treatment systems and hence recommended for adoption. A salient feature of the study is the introduction of biomat concept and its contribution in the overall treatment process.

Optimal Operation of Soil Aquifer Treatment Systems Considering Parameter Uncertainty

This paper presents a new methodology for determining optimal operation of soil aquifer treatment (SAT) systems considering parameter uncertainty. The problem of optimal operation of SAT systems is formulated and solved in a discrete-time optimal control framework by interfacing the SALQR (Successive Approximation Linear Quadratic Regulator) optimizer with the MSTS (Multiphase Subsurface Transport Simulator) model. Both deterministic and stochastic programming formulations have been solved. Through the use of first-order analysis of uncertainties, the uncertainty of the water content due to the uncertainties of the simulation parameters are evaluated. A chance constrained formulation of the optimization is utilized to account for the uncertainties of water content in the SAT operation. This approach enables one to quantify the uncertainty of the parameter estimates, and automatically account for the parameter uncertainty in the decision-making process through the SAT management model.

New Methodology for Optimal Operation of Soil Aquifer Treatment Systems

A new methodology is presented in thisarticle for computing the optimal operation of soilaquifer treatment systems. The mathematical problemis stated as a discrete-time optimal control problemto maximize infiltration subject to various physicaland operation constraints. The methodology is basedupon solving the discrete-time optimal control problemusing a successive approximation linear quadraticregulator interfaced with a simulator. Theunsaturated flow model HYDRUS is modified to simulatethe water content distribution, the infiltrationprocess, and the draining process. A penalty functionmethod is used to treat the bound constraints on thewater content and the cycle time. Sample problems aregiven to illustrate the capability of the model tosolve the optimal operation of soil aquifer treatment systems.

Behavior of DOC and AOX using advanced treated wastewater for groundwater recharge

Laboratory studies with continuous-flow columns containing aquifer material were conducted to evaluate the potential of sorption and biodegradation of halogenated organic compounds (AOX) and dissolved organic carbon (DOC) in tertiary effluents during soil–aquifer treatment (SAT). To improve water quality, powdered activated carbon (PAC) treatment and the use of ozone were also investigated. Batch experiment results indicated that sorption processes are not significant concerning DOC and AOX removal in SAT. Biodegradation of DOC during SAT can be described by a first-order macroscopic kinetic model. However, 65% of DOC was not biodegradable during SAT. These refractory compounds are similar to humic and fulvic acids and are probably formed in the activated sludge treatment or are present already in the drinking water which has a DOC level of 3–5mgl−1. The elimination of AOX under anoxic conditions is probably based on cometabolism. Poorly degradable DOC does function as a cosubstrate in AOX-cometabolism and it is likely that further AOX-degradation will occur until local background concentration are reached. PAC (100gm−3 W-35, Norit Co.) preferentially adsorbed refractory, high molecular weight fractions and up to 50% of the AOX concentration in tertiary effluent was reduced. Ozone treatment (0.86 and 1.89g O3g−1 DOC0) improved the biodegradability of refractory organic compounds and cosubstrate concentration for AOX-cometabolism in subsequent SAT. This research concludes, that refractory DOC is more important in soil–aquifer treatment systems than AOX compounds, commonly considered to be of greater concern.

Genetic algorithms for optimal operation of soil aquifer treatment systems

The genetic algorithm (GA) is a nonconventional search technique which is patterned after the biological processes of natural selection and evolution. It has the ability to search large and complex decision spaces and handle nonconvexities. In this paper, the genetic algorithm is investigated and applied to solve the optimal operation problem of soil aquifer treatment (SAT) systems. This problem involves finding optimal water application time and drying time which maximize infiltration for a predetermined starting influent rate of waste water and subject to various physical and operational constraints. A new scaling method is developed and some improvements on the evolution procedure are presented. A comprehensive GA–SAT computer model was developed and applied to an example SAT problem. The results are encouraging, when compared with using the successive approximation linear quadratic regulator algorithm. It was found that genetic algorithms are easy to program and interface with large complicated simulators.

Development of methodology for the optimal operation of soil aquifer treatment systems

Soil aquifer treatment (SAT) systems are used for reclamation of sewage effluent by groundwater recharge. Increasing demand on water supplies has stimulated the production or planning of many SAT systems that will use reclaimed wastewater for groundwater recharge. These systems are comprised of a series of infiltration basins. The design and operation of soil aquifer treatment systems presently relies primarily upon judgment and experience. This research effort is developing a methodology for determining the optimal operation of SAT systems that is based upon mathematically describing the problem as a discrete-time optimal control problem. The resulting mathematical problem is a large-scale nonlinear programming problem. Solution of the problem is being accomplished by interfacing a nonlinear programming optimizer, which is solved by a differential dynamic programming algorithm, with a simulator that describes the infiltration process, unsaturated flow, effects of surface clogging and biological clogging, biological removal of nitrogen and organics. Major efforts are devoted to numerical performance of the optimization model solution, and development of the simulator. Initial results of interfacing the optimizer with the simulator without water quality concern show high convergence rate. The operation pattern determined by this method is reasonable. This new methodology will be a tool for engineers to evaluate choices regarding the potential of the design and operation of SAT systems.

Retardation factors and breakthrough times of organic micropollutants in groundwater recharged with effluents

In the Dan Region Reclamation Center (DRRC) in Israel, secondary effluents, after a mechanical - biological treatment and polishing ponds, undergo a Soil-Aquifer Treatment (SAT), in the course of which these are recharged into an isolated aquifer, and the repumped water is used for various agricultural purposes. In the present study a simple model has been developed in order to predict retardation factors and breakthrough times of various micropollutants in the SAT system. The model is based on the linear free energy relationship between adsorbtivity of organic compounds and their hydrophobicity as expressed by their octanol - water partition coefficients. A very good correlation was found between the predicted values calculated by the model, and experimental laboratory results of adsorption isotherms and breakthrough curves.

Development of methodology for the optimal operation of soil aquifer treatment systems

Soil aquifer treatment (SAT) systems are used for reclamation of sewage effluent by groundwater recharge. Increasing demand on water supplies has stimulated the production or planning of many SAT systems that will use reclaimed wastewater for groundwater recharge. These systems are comprised of a series of filtration basins. The design and operation of soil aquifer treatment systems presently relies primarily upon dgment and experience. This research effort is developing a methodology for determining the optimal peration of SAT systems that is based upon mathematically describing the problem as a discrete-time ptimal control problem. The resulting mathematical problem is a large-scale nonlinear programming problem. Solution of the problem is being accomplished by interfacing a nonlinear programming optimizer, which is solved by a differential dynamic programming algorithm, with a simulator that describes the filtration process, unsaturated flow, effects of surface clogging and biological clogging, biological removal of nitrogen and organics. Major efforts are devoted to numerical performance of the optimization model elution, and development of the simulator. Initial results of interfacing the optimizer with the simulator without water quality concern show high convergence rate. The operation pattern determined by this method reasonable. This new methodology will be a tool for engineers to evaluate choices regarding the potential of the design and operation of SAT systems.

Retardation factors and breakthrough times of organic micropollutants in groundwater recharged with effluents

In the Dan Region Reclamation Center (DRRC) in Israel, secondary effluents, after a mechanical - biological treatment and polishing ponds, undergo a Soil-Aquifer Treatment (SAT) , in the course of which these are recharged into an isolated aquifer, and the repumped water is used for various agricultural purposes. In the present study a simple model has been developed in order to predict retardation factors and breakthrough times of various micropollutants in the SAT system. The model is based on the linear free energy relationship between adsorbtivity of organic compounds and their hydrophobicity as expressed by their octanol - water partition coefficients. A very good correlation was found between the predicted values calculated by the model, and experimental laboratory results of adsorption isotherms and breakthrough curves.

Optimum Operation of Recharge Basins

Mathematical models based on nonlinear programming are developed for operating recharge-basin systems (also referred to as soil-aquifer treatment systems). The objective of these optimization models is to determine the operation policy (loading schedules) that maximizes the infiltration volume subject to constraints for continuity, infiltration, ground-water flow, and the physical constraints describing the recharge basins. Two basic physical processes that are involved in the recharge-basin systems are the infiltration process and the soil-moisture–redistribution process. The infiltration process is modeled using both the Philip’s and the Green-Ampt infiltration models, and the soil-moisture redistribution process is modeled using Darcy’s equation as well as a kinematic-wave model. An improvement on the developed models is to consider the final moisture content at the end of each cycle time as a decision variable; which also allows the total cycle time to become a decision variable. In the modified applications, the objective is changed to maximizing the infiltration rate instead of maximizing the infiltration volume. Several hypothetical applications are presented to illustrate the modeling procedure.

Role of Groundwater Recharge in Treatment and Storage of Wastewater for Reuse

Reuse of municipal wastewater requires treatment so that the water meets the quality requirements for the intended use. Irrigation of vegetables consumed raw requires absence of pathogenic organisms. To achieve this, fecal coliform concentrations should be essentially zero and the water should be filtered. This requires intensive treatment. For developing countries, however, where adequate sewage treatment often is lacking, the World Health Organization allows up to 1000 fecal coliform bacteria per 100 ml, which can be obtained by lagooning. Potable reuse requires much more intensive treatment, including lime clarification, denitrification, carbon adsorption, reverse osmosis, and disinfection. Where hydrogeologic conditions permit groundwater recharge with surface infiltration facilities, considerable water quality improvement is obtained by the movement of the wastewater through the soil, vadose zone, and aquifer. The resulting soil-aquifer treatment costs are less than 40% of the costs of equivalent in-plant treatment. Soil-aquifer treatment systems also are simple and robust, offer storage of the water to absorb differences between supply and demand, and enhance the aesthetics of potable reuse of wastewater. Hence, they can play an important role in wastewater reuse.