Optimal Location and Management of Waste Disposal Facilities Affecting Ground Water Quality1

ABSTRACT: Numerical simulation of ground water solute transport is combined with linear programming to optimize waste disposal. A discretized form of the equation governing solute transport is included as a set of constraints in a linear program. Two problems are described. First, the management model is used to maximize ground water waste disposal. The model constrains disposal activities so that the quality of local ground water supplies is protected. Parametric programming is shown to be important in evaluating waste disposal tradeoffs at the various facilities. Changes in the velocity field induced by waste water injection cause a nonlinearity in the solute transport equation which is dealt with by employing an iterative procedure. The second problem is aimed at identifying all sites which are suitable for waste disposal in the subsurface. The management model is manipulated so that the optimal value of the dual variables are “unit source impact indicators.” This physical interpretation is valuable in identifying feasible disposal sites. The joint simulation and optimization approach permits the management of complex ground water systems where the aquifer is used simultaneously for waste disposal and water supply.     

INCREASING WATER SUPPLY BY MIXING OF FRESH AND SALINE GROUND WATERS1

ABSTRACT: The quality of ground water in any aquifer takes its final form due to natural mixture of waters, which may originate from different sources. Water quality varies from one aquifer to another and even within the same aquifer itself. Different ground water quality is obtained from wells and is mixed in a common reservoir prior to any consumption. This artificial mixing enables an increase in available ground water of a desired quality for agricultural or residential purposes. The question remains as to what proportions of water from different wells should be mixed together to achieve a desired water quality for this artificial mixture. Two sets of laboratory experiments were carried out, namely, the addition of saline water to a fixed volume of fresh water. After each addition, the mixture volume and the electric conductivity value of the artificially mixed water were recorded. The experiments were carried out under the same laboratory temperature of 20°C. A standard curve was developed first experimentally and then confirmed theoretically. This curve is useful in determining either the volume or discharge ratio from two wells to achieve a predetermined electrical conductivity value of the artificial mixture. The application of the curve is given for two wells within the Quaternary deposits in the western part of the Kingdom of Saudi Arabia.     

RECLAIMED WASTE WATER FOR GROUNDWATER RECHARGE1

ABSTRACT. The Orange County Water District has conducted studies in waste water reclamation and groundwater recharge since 1965. The work has been done in three phases: (1) Study in both laboratory and pilot-scale units on the feasibility of reclaiming trickling filter effluent for injection through wells into confined aquifers; (2) long-term injection study to determine the fate of injected reclaimed water and to observe the performance of a multi-casing injection well; (3) testing alternative treatment methods in a 25,000 gpd pilot plant to solve the water quality problems which developed during the injection study. The reclaimed trickling filter effluent was found to be injectable and did not cause excessive well clogging. The multi-casing injection wells performed very satisfactorily. The reclaimed water would be acceptable for domestic use after travel through 500 feet of a confined aquifer in that bacteria, virus and toxic material were consistently absent. However, the odor and taste which persisted in the injected reclaimed water and the high concentration of dissolved inorganics are undesirable characteristics. Methods to eliminate the odor are being tested at the present time. A cooperative project with the Office of Saline Water is under way to develop a source of desalted seawater to blend with reclaimed waste water.     

OCCURRENCE OF PESTICIDES IN GROUND WATER OF THE OZARK PLATEAUS PROVINCE1

ABSTRACT: Pesticides were detected in ground-water samples collected from 20 springs and nine wells in the Ozark Plateaus Province of Arkansas, Kansas, Missouri, and Oklahoma. From April through September 1993, water samples were collected from 50 shallow domestic wells and 50 springs in the Springfield Plateau and Ozark aquifers and analyzed for 47 pesticides and metabolites. Pesticides were detected in 17 water samples from the Springfield Plateau aquifer and 12 water samples from the Ozark aquifer. Fourteen pesticides were detected, with a maximum of four pesticides detected in any one sample. The most commonly detected pesticides were atrazine (14 detections), prometon (11 detections), and tebuthiuron (seven detections). P, P' DDE, a metabolite of DDT, was detected in water samples from three wells and one spring. The remaining pesticides were detected in three or less samples. The occurrence and distribution of pesticides probably are related to the local land use near a sampling site. Pesticide detections were significantly related to aquifer, site type, and discharge of springs.     

A Stochastic Modeling Approach to Address Hydrogeologic Uncertainties in Modeling Wellhead Protection Boundaries in Karst Aquifers1

Abstract: Development of any numerical ground‐water model is dependent on hydrogeologic data describing the subsurface. These data are obtained from geologic core analyses, stratigraphic analyses, aquifer performance tests, and geophysical studies. But typically in remote areas, these types of data are very sparse and site‐specific in terms of the aerial extent of the resource to be modeled. Uncertainties exist as to how well the available data from a few locations defines a heterogeneous surficial aquifer such as the Biscayne Aquifer in Miami‐Dade County, Florida. This is particularly the case when an exceptionally conductive horizontal flow zone is detected at one site due to specialized testing that was not historically conducted at the other at sites that provided data for the model. Not adequately accounting for the potential effect of the high flow zone in the aquifer within a ground‐water numerical model, even though the zone may be of very limited thickness, might underpredict the well field protection capture boundaries. Applied Stochastic ground‐water modeling in determining well field protection zones is steadily becoming important in addressing the uncertainty of the hydrogeologic subsurface parameters, specifically in karstic heterogeneous aquifers. This is particularly important in addressing the uncertainty of a 60‐day travel time capture zone in the Northwest Well Field, Miami‐Dade County, where a predominantly high flow zone controls much of the flow in the production wells. A stochastic ground‐water modeling application along with combination of pilot points and regularization technique is presented to further consolidate the uncertainty of the subsurface.     

IMPACT OF IRRIGATION WELLS ON BASEFLOW OF THE BIG BLUE RWER,NEBRASKA1

ABSTRACT: The Kansas-Nebraska Big Blue River compact requires that the state of Nebraska insure a minimum flow of the Big Blue River across the state line. There are two options that the state of Nebraska may use to ensure minimum flows. The obvious option is to limit surface-water irrigators along the river. However, under the terms of the compact, a second option may be to regulate irrigation wells that are within one mile of the river and were installed after November 1, 1968. The objective of this study is to quantify the effects of 17 irrigation wells that may be regulated on baseflow of the Big Blue River. A finite-element model is used to study the hydrogeologic system between DeWitt and Beatrice, Nebraska. The 17 wells that may be regulated are located between these towns and are developed in sediments deposited in a cross-cutting paleovalley anchor alluvium associated with the Big Blue River. While there wore considerable existing data, additional data were gathered by drilling an additional nine test holes, conducting several aquifer tests, stream-stage measurements, and baseflow calculation through extensive stream-discharge measurements, establishment of a ground water-level monitoring network, determining the amount of water pumped for irrigation and municipal use in the area, and a short-term precipitation network. The model was calibrated using observed baseflow and ground water level data. The model clearly shows that regulating the 17 wells to maintain baseflow would have a minimal effect on the overall water budget. This is reasonable, especially considering that there are over 250 irrigation wells in the project area. The 17 wells considered pumped only 6 percent of the total pumpage within the modeled area during the irrigation season of 1984. The computer model provides the documentation needed to demonstrate this fact. Although much of the resources spent and a significant amount of hydrogeologic data are being collected over a period of three years on a relatively small area, the simulation model could be improved through further field testing of the aquifer and stream-bed sediment characteristics and quantification of ground water recharge, discharge, and evapotranspiration rates.     

Relative merits of polystyrene foam and paper in hot drink cups: Implications for packaging

An analysis of the overall relative merits of the use of uncoated paper vs molded polystyrene bead foam in single-use 8-oz cups is described here as a manageable example of the use of paper vs plastics in packaging. In raw material requirements the paper cup required about 2.5 times its finished weight of raw wood and about the same hydrocarbon fueling requirement as is needed for the polystyrene foam cup. To process the raw materials about six times as much steam, 13 times as much electric power, and twice as much cooling water are consumed to produce the paper cup as compared to the polystyrene foam cup. Emission rates to air are similar and to water are generally higher for the paper cup. Virtually all primary use factors favor polystyrene foam over paper. Once used both cup types may be recycled. Landfill disposal of the two items under dry conditions will occupy similar landfill volumes after compaction and will confer similarly slow to nonexistent decomposition to either option. Under wet conditions polystyrene foam will not readily degrade, but may help other materials to do so. Paper under wet conditions will biodegrade to produce methane, a significant greenhouse gas, biochemical oxygen demand to any leachate, and instability to the land surface during the process. Both materials can be incinerated cleanly in a municipal waste stream with the option of energy recovery, to yield an ash volume of 2%–5% of the incoming waste volume. Overall this analysis would suggest that polystyrene foam, with an extension to plastics in general, should be given more evenhanded consideration relative to paper in packaging applications than is currently the case.     

MODELING CONCENTRATION VARIATIONS IN HIGH-CAPACITY WELLS: IMPLICATIONS FOR GROUNDWATER SAMPLING1

ABSTRACT: High-capacity wells are used as a convenient and economical means of sampling groundwater quality. Although the inherent limitations of using these wells are generally recognized, little has been done to investigate how these wells actually sample groundwater. A semi-analytical particle tracking model is used to illustrate the influence of variable vertical contaminant distributions and aquifer heterogeneity on the composition of water samples from these wells during short pumping periods. The hypothetical pumping well used in the simulations is located in an unconfined, alluvial aquifer with a shallow water table and concentration gradients of nitrate-nitrogen contamination. This is a typical setting for many irrigated areas in the United States. The main conclusions are: (1) high-capacity wells underestimate the average amount of contamination within an aquifer; (2) shapes of concentration-time curves for high-capacity wells appear to be governed by the distribution of the contaminant and travel times to the well; (3) variables such as well construction, pumping rate, and hydrogeologic properties contribute to the magnitude of the concentration-time curves at individual high-capacity wells; and (4) a sampling strategy using concentration-time curves based on the behavioral characteristics of the well rather than individual samples will provide a much better framework for interpreting spatial contaminant distributions.     

Life-Cycle Impact Assessment of oil drilling mud system in Algerian arid area

The objective of this work is to assess the environmental impacts of the drilling mud system in Algeria's arid region. Water-based mud (WBM) and oil-based mud (OBM) are used during well drilling in Hassi Messaoud petroleum field, and have a considerable pollution potential particularly on the aquifer system which constitutes the single resource of drinking water in the Sahara. The Life-Cycle Assessment (LCA) approach is applied to evaluate the impacts of several drilling mud systems across all stages of their life cycle, e.g. use, treatment and disposal. Environmental impacts of five treatments scenarios corresponding to the drilling waste management applied in Hassi Messaoud are compared: reserve pit without treatment (burial option), secondary high centrifugation (vertical cuttings dryer), stabilisation/solidification online, stabilisation/solidification off line and thermal desorption. The impact assessment is carried on using the LCIA models of Impact 2002+ method in SIMAPRO7 software. This assessment identifies human toxicity and terrestrial eco-toxicity as the major impact categories in this specific arid context and quantifies the emissions contributions. The local environmental impact is the most important of the drilling mud life cycle and is mainly linked to emissions from reserve pits, treated cuttings, and drilling phase 16″ through the Turonian and Albian aquifer. The main contributing substances are aromatic hydrocarbons fraction and metals in particular barium, zinc, antimony, arsenic, and aluminium. Concerning the comparison of the treatment scenarios, it appears that stabilisation/solidification online is the best one; it has the lowest impact score in the two dominating categories because of the waste minimisation: mud storage avoided in the reserve pit. The second best scenario is the thermal desorption which obtains the lowest impact score in carcinogen effects due to hydrocarbons reduction (<1%) and avoided impacts of recovered oil. The toxic substances fate modeling will be improved by taking into account their site-specific impact.     

An approach to tackling the environmental and health impacts of municipal solid waste disposal in developing countries

Indiscriminate disposal of municipal solid waste in developing countries poses severe environmental and health threats. The study proposes a new method for dealing with these problems. The hybrid structural interaction matrix (HSIM) was used to prioritise major identifiable environmental health factors arising from improper solid waste disposal. The simplistic resource allocation model was adopted to ensure optimality in the allocation of resources to prioritised factors. The study indicates that tackling environmental health impacts from the most prioritised negative disposal factors through optimal allocation of resources, will either reduce or eliminate the impacts associated with subsequent less prioritised factors that are direct consequences of the highly prioritised negative factors. The method proposed will aid decision makers in knowing which set of systemic factors are to be given preference and to what extent at given periods in time.     

IDENTIFICATION OF AN OPTIMAL GROUNDWATER MANAGEMENT STRATEGY IN A CONTAMINATED AQUIFER1

A groundwater hydraulic management model is used to identify the optimal strategy for allocating limited fresh-water supplies and containing wastes in a hypothetical aquifer affected by brine contamination from surface disposal ponds. The present cost of pumping from a network of potential supply and interception wells is minimized over a five-year planning period, subject to a set of hydraulic, institutional, and legal constraints. Hydraulic constraints are formulated using linear systems theory to describe drawdown and velocity variables as linear functions of supply and interception well discharge decision variables. Successful validation of the optimal management strategy suggests that the model formulation can feasibly be applied to define management options for locally contaminated aquifer systems which are used to fulfill fresh-water demands.     

An Aquifer Storage and Recovery system with reclaimed wastewater to preserve native groundwater resources in El Paso, Texas

The traditional concept of Aquifer Storage and Recovery (ASR) has been emphasized and extensively applied for water resources conservation in arid and semi-arid regions using groundwater systems as introduced in Pyne's book titled Groundwater Recharge and Wells. This paper extends the ASR concept to an integrated level in which either treated or untreated surface water or reclaimed wastewater is stored in a suitable aquifer through a system of spreading basins, infiltration galleries and recharge wells; and part or all of the stored water is recovered through production wells, dual function recharge wells, or by streams receiving increased discharge from the surrounding recharged aquifer as needed. In this paper, the author uses the El Paso Water Utilities (EPWU) ASR system for injection of reclaimed wastewater into the Hueco Bolson aquifer as an example to address challenges and resolutions faced during the design and operation of an ASR system under a new ASR system definition. This new ASR system concept consists of four subsystems: source water, storage space-aquifer, recharge facilities and recovery facilities. Even though facing challenges, this system has successfully recharged approximately 74.7 million cubic meters (19.7 billion gallons) of reclaimed wastewater into the Hueco Bolson aquifer through 10 recharge wells in the last 18 years. This ASR system has served dual purposes: reuse of reclaimed wastewater to preserve native groundwater, and restoration of groundwater by artificial recharge of reclaimed wastewater into the Hueco Bolson aquifer.     

EDWARDS AQUIFER EVALUATION: KINNEY COUNTY,TEXAS1

ABSTRACT: The Edwards Aquifer is one of the most studied and most prolific aquifers in the United States. The aquifer is a heavily fractured and faulted carbonate aquifer with transmissivities in excess of 100 ft²/s. The City of San Antonio relies upon the Edwards Aquifer as its sole source for water. Much work has been done on quantifying recharge to the aquifer and discharge from wells and acquiring aquifer characteristics from pumping tests, specific capacity tests, and geophysical logs. Although the aquifer has been well studied in Bexar County, much less is known about the Edwards Aquifer in Kinney County. This is partly due to the lower population within the county (approximately 3,500 people) relative to the eastern counties (Uvalde, Medina, Bexar, Comal, and Hays) and the great distance of Kinney County from high profile discharge areas such as the City of San Antonio and Comal and San Marcos Springs. Three key products resulted from this study: (1) exploratory well drilling and the largest aquifer test in the county that were conducted to evaluate the well yields within a 10,000 acre study area in which a drawdown of 2.5 ft approximately 1.2 miles away was observed while pumping at approximately 4,600 gpm; (2) a recharge estimate for the Edwards Aquifer within Kinney County of approximately 71,382 ac‐ft/yr; and (3) locating the Brackettville Groundwater Divide from an evaluation of ground water flow direction and hydrograph analysis. These results help evaluate the complex hydraulics occurring within Kinney County and aid in development of ground water modeling that will be used in managing the Edwards Aquifer.     

UTILIZATION OF A GEOGRAPHIC INFORMATION SYSTEM TO IDENTIFY THE PRIMARY AQUIFER PROVIDING GROUND WATER TO INDWIDUAL WELLS IN EASTERN ARKANSAS1

ABSTRACT: A Geographic Information System (GIS) was used to develop an automated procedure for identifying the primary aquifers supplying ground water to individual wells in eastern Arkansas. As mandated by state law, water-use data are reported by ground-water withdrawers annually to the Arkansas Soil and Water Conservation Commission, and stored in the Arkansas Site-Specific Water-Use Data System provided and supported by the U.S. Geological Survey. Although most withdrawers are able to provide the amount of water withdrawn and the depth of their wells, very few are able to provide the name of the aquifer from which they withdraw water. GIS software was used to develop an automated procedure for identifying the primary aquifers supplying ground water to individual wells in eastern Arkansas. The software was used to generate a spatial representation of the bottom boundary for the Mississippi River Valley alluvial aquifer (the shallowest aquifer) in eastern Arkansas from well log-data collected by the U.S. Geological Survey. The software was then used to determine the depth of the aquifer bottom at reported well locations to ascertain whether the Mississippi River Valley alluvial aquifer or a deeper aquifer was the primary aquifer providing water to each well. The alluvial aquifer was identified as the primary aquifer for about 23,500 wells.     

Sustainable three‐well pumping strategy for efficient detection monitoring near waste impoundments

Efficient monitoring systems addressing the difficulty of detecting narrow contaminant plumes originating from unknown point sources are needed for modern landfills. A low‐discharge extraction and accompanying injection wells could potentially address this problem. This hypothetical computer‐modeling study involved a three‐well detection system consisting of one extraction and two injection wells at a rectangular landfill in a shallow, unconfined aquifer. The extraction and injection wells were located near the landfill's downgradient and cross‐gradient corners, respectively. Each injection well pumped at half the rate of the extraction well. A minimum pumping rate of 1.1 cubic meters per day was determined for the three‐well system; at this rate, all contaminant plumes originating within the landfill's footprint entered the extraction well prior to reaching a downgradient property boundary. In comparison, five passive (not pumped) wells detected all contaminant releases from the landfill. Results of this study suggest that a low‐discharge extraction well with accompanying injection wells may be an effective contaminant detection strategy at some waste impoundments.     

Quality of Water from Hand Dug Wells in Onitsha Metropolitan Areas of Nigeria

Summary Wide Range of human and anthropogenic activities impinges on the urban environment in most cities in Nigeria, to degrade the quality of water resources. Some of these activities (daily discharge of solid and liquid waste, industrial effluent, and physo-chemical weathering processes) are discharged directly on sources of water supply to the populace of Onitsha. Based on this problem, this paper examines the quality of water from hand-dug wells in Onitsha. 15 wells water samples were collected during the month of January, July, and August with the aid of sterilized containers. And sent to the laboratory for analyses, results showed that wells that are located close to dumpsites are more polluted in terms of turbidity, TSS, CaCo₂ conductivity salinity acidity, Pb, Fe and bacteriological quality of the well water. Also most of the hand-dug well water qualities are unsafe for human consumption, because they are generally above the WHO maximum acceptable threshold. Since this source of water form one of the major source of water to the inhabitants, there is need for purification proper disposal of waste, public education of the health implication of waste/impure water and other management measures.     

MULTICRITERION ANALYSIS OF GROUNDWATER CONTAMINATION MANAGEMENT1

ABSTRACT: Multicriterion decision making (MCDM) techniques were used to analyze a groundwater contamination management problem from the viewpoint of conflicting multiple objectives. The groundwater management model was used to find a compromise strategy for trading off fresh water supply, containment of the waste, and total pumping cost in a hypothetical confined aquifer affected by previous waste disposal action. A groundwater flow model was used to formulate the hydraulic constraints. A linear system model was used to describe drawdown and velocity as functions of the decision variables which were pumping rates. The model determines the pumping location and rates. A modified c-constraint method was used to generate the set of nondominated solutions which were the alternative compromise strategies. Three different MCDM techniques, Compromise programming (CP), ELECTRA II and MCQA II, were used to select a “satisficing” alternative. Analysis of the results showed that, although these techniques follow different principles, the same preferred strategies were reached. Also, it was noticed that maintaining high groundwater velocities is expensive and difficult. In order to meet a two year target date, large amounts of water had to be pumped. Therefore, rapid restoration results in large pumping volumes and high costs.     

固体废物全过程管理中固体废物鉴别研究

对固体废物应进行全过程管理,固体废物鉴别是固体废物全过程管理的基础和关键,包括依据产生来源鉴别和过程鉴别两种方法,依据产生来源鉴别包括丧失原有利用价值的物质、在生产过程中产生的副产物、环境治理和污染控制过程中产生的物质、其他物质四类,在每一类中详细地列举了属于该产生来源的具体固体废物种类名称,便于理解和增强可操作性。过程鉴别包括在固体废物再生利用过程和处置过程中的固体废物鉴别两类,其中在再生利用过程的固体废物鉴别中明确指出了固体废物再生利用产物只有同时满足产品质量标准要求、国家污染控制标准要求以及有实际市场需求、固定用户等条件时,才不作为固体废物管理,在处置过程的固体废物鉴别中具体地列出了处置固体废物全过程中仍然作为固体废物管理的国际惯用处置方式。同时,给出了清晰的"原料—产品—固体废物—处置或产品"全过程中固体废物的产生节点和相应的固体废物类别图,为固体废物鉴别工作提供参考,使固体废物全过程管理有的放矢,有效防止固体废物对环境和人体健康造成的危害。     

RESULTS OF ACIDIZING WATER WELLS IN ARIZONA1

Two wellfields have been developed to provide water for a coal fired electric generating station in Arizona. Wellfield No. 1 penetrates the unconfined Coconino Sandstone aquifer, and wellfield No. 2 penetrates the composite Kaibab Limestone-Coconino Sandstone aquifer where ground water occurs under confined conditions. A well in each wellfield was pumped and water level drawdown data were collected before and after acidizing. The drawdown data at the various pumping rates were analyzed to determine the potential benefits of acidizing production water wells in both wellfields. After acidizing, the specific capacity of the well in wellfield No. 1 was improved about 50 percent at water production rates ranging from about 200 to 500 gallons per minute (gpm) (13 to 32 liters per second (lps)). After acidizing, the specific capacity of the well completed in wellfield No. 2 was improved about 100 percent at pumping rates ranging from about 1,250 to 2,200 gpm (79 to 139 lps). An annual saving of approximately 11 percent in pumping costs can be realized in wellfield No. 2, and savings are approximately four percent in wellfield No. 1. Acidization is beneficial for wells that can produce more than 500 gpm (32 lps), and is of marginal value for those that produce less than that amount.     

The Transboundary Nature of the Allende–Piedras Negras Aquifer Using a Numerical Model Approach

The Allende–Piedras Negras (APN) aquifer is located between the states of Texas (United States [U.S.]) and Coahuila (Mexico). The Rio Grande crosses the aquifer, acting as a natural and political divide between the countries. However, it remains unclear whether the APN aquifer can be considered a truly transboundary aquifer flow system, which would potentially require joint management by two different administrative jurisdictions. The main purpose of this study was to evaluate the transboundary nature of this aquifer. This was achieved by developing a detailed hydrogeological model to analyze the direction of volumetric fluxes within the APN aquifer using Visual MODFLOW. The model simulated a spatially averaged cumulative drawdown of 0.76 m for the entire aquifer over an 18‐year modeling period (2000–2017). The flow convergence zone, previously located below the Rio Grande, has shifted to the U.S. side in most locations, driven by higher pumping rates of the wells located near the river. This shift of the convergence zone from one country to the other means that groundwater recharge from one side flows underneath the river to the other side. This qualifies the APN aquifer as a “transboundary groundwater flow system.” The procedure followed in this study may be applied to other aquifers that straddle the U.S.–Mexico border and may motivate future modeling studies on other poorly studied transboundary aquifers around the world and thereby enable bi‐national aquifer management.