Environmental engineering. Vol. 1, Water, wastewater, soil and groundwater treatment and remediation

First published in 1958, Salvato's Environmental Engineering has long been the definitive reference for generations of sanitation and environmental engineers. Approaching its fiftieth year of continual publication in a rapidly changing field, the Sixth Edition has been fully reworked and reorganized into three separate, succinct volumes to adapt to a more complex and scientifically demanding field with dozens of specializations. Updated and reviewed by leading experts in the field, this revised edition offers new process and plant design examples and added coverage of such subjects as urban and rural systems. Stressing the practicality and appropriateness of treatment, the Sixth Edition provides realistic solutions for the practicing public health official, water treatment engineer, plant operator, and others in the domestic and industrial waste treatment professions. This volume, __Environmental Engineering: Water, Wastewater, Soil and Groundwater Treatment and Remediation, Sixth Edition__, covers: * Water treatment * Water supply * Wastewater treatment Content: Chapter 1 Water Supply (pages 1–131): T. David ChinnChapter 2 Water Treatment (pages 133–281): T. David ChinnChapter 3 Wastewater Treatment and Disposal (pages 283–370): John R. Kiefer

Excerpt

CHAPTER 1

WATER SUPPLY

T. DAVID CHINN Professional Engineer, Senior Vice President, HDR Engineering, Austin, Texas

INTRODUCTION

A primary requisite for good health is an adequate supply of water that is of satisfactory sanitary quality. It is also important that the water be attractive and palatable to induce its use; otherwise, consumers may decide to use water of doubtful quality from a nearby unprotected stream, well, or spring. Where a municipal water supply passes near a property, the owner of the property should be urged to connect to it because such supplies are usually under competent supervision.

When a municipal water supply is not available, the burden of developing a safe water supply rests with the owner of the property. Frequently, private supplies are so developed and operated that full protection against dangerous or objectionable pollution is not afforded. Failure to provide satisfactory water supplies in most instances must be charged either to negligence or ignorance because it generally costs no more to provide a satisfactory installation that will meet good health department standards.

The following definitions are given in the National Drinking Water Regulations as amended through July, 2002:

Public water system means either a community or noncommunity system for the provision to the public of water for human consumption through pipes or other constructed conveyances, if such system has at least 15 service connections, or regularly serves an average of at least 25 individuals daily at least 60 days out of the year. Such a term includes (1) any collection, treatment, storage, and distribution facilities under the control of the operator of such system and used primarily in connection with such system, and (2) any collection or pretreatment storage facilities not under such control which are used primarily in connection with such system.

A community water system has at least 15 service connections used by year-round residents, or regularly serves at least 25 year-round residents. These water systems generally serve cities and towns. They may also serve special residential communities, such as mobile home parks and universities, which have their own drinking water supply.

A noncommunity water system is a public water system that is not a community water system, and can be either a "transient noncommunity water system" (TWS) or a "non-transient noncommunity water system" (NTNCWS). TWSs typically serve travelers and other transients at locations such as highway rest stops, restaurants, and public parks. The system serves at least 25 people a day for at least 60 days a year, but not the same 25 people. On the other hand, NTNCWSs serve the same 25 persons for at least 6 months per year, but not year round. Some common examples of NTNCWSs are schools and factories (or other workplaces) that have their own supply of drinking water and serve 25 of the same people each day.

In 2007 there were approximately 156,000 public water systems in the United States serving water to a population of nearly 286 million Americans. There were approximately 52,110 community water systems, of which 11,449 were surface water supplies and 40,661 were groundwater supplies. There were 103,559 noncommunity water systems, of which 2557 were surface water supplies and 101,002 were groundwater supplies. Of the community water systems, 43,188 are small systems that serve populations less than 3300; 4822 are medium systems and serve populations between 3300 and 10,000; and 4100 are large systems serving populations over 10,000. In terms of numbers, the small and very small community and noncommunity water systems represent the greatest challenge to regulators and consultants—both contributing to over 88 percent of the regulatory violations in 2007.1

In addition to public water systems, the U.S. Geological Survey estimated that 43.5 million people were served by their own individual water supply systems in 2000. These domestic systems are—for the most part—unregulated by either state or county health departments.

A survey made between 1975 and 1977 showed that 13 to 18 million people in communities of 10,000 and under used individual wells with high contamination rates. The effectiveness of state and local well construction standards and health department programs has a direct bearing on the extent and number of contaminated home well-water supplies in specific areas.

A safe and adequate water supply for 2.4 billion people, about one-third of the world's population, is still a dream. The availability of any reasonably clean water in the less-developed areas of the world just to wash and bathe would go a long way toward the reduction of such scourges as scabies and other skin diseases, yaws and trachoma, and high infant mortality. The lack of safe water makes high incidences of shigellosis, amebiasis, schistosomiasis, leptospirosis, infectious hepatitis, giardiasis, typhoid, and paratyphoid fever commonplace. Ten million persons suffer from dracunculiasis or guinea worm disease in Africa and parts of Asia. The World Health Organization (WHO) estimates that some 3.4 million people die each year from water-borne diseases caused by microbially contaminated water supplies or due to a lack of access to sanitation facilities. Tragically, over one half of these deaths are children under the age of five years old. Three-fourths of all illnesses in the developing world are associated with inadequate water and sanitation. It is believed that the provision of safe water supplies, accompanied by a program of proper excreta disposal and birth control, could vastly improve the living conditions of millions of people in developing countries of the world. In 1982, an estimated 46 percent of the population of Latin America and the Caribbean had access to piped water supply and 22 percent had access to acceptable types of sewage disposal.

The diseases associated with the consumption of contaminated water are discussed in Chapter 1 of Environmental Engineering, Sixth Edition: Prevention and Response to Water-, Food-, Soil,- and Air-Borne Disease and Illness and summarized in Table 1.4 of that volume.

Groundwater Pollution Hazard

Table 1.1 shows a classification of sources and causes of groundwater pollution. The 20 million residential cesspool and septic tank soil absorption systems alone discharge about 400 billion gallons of sewage per day into the ground, which in some instances may contribute to groundwater pollution. This is in addition to sewage from restaurants, hotels, motels, resorts, office buildings, factories, and other establishments not on public sewers. The contribution from industrial and other sources shown in Table 1.1 is unknown. It is being inventoried by the EPA, and is estimated at 900 billion gal/year, the EPA, with state participation, is also developing a groundwater protection strategy. Included in the strategy is the classification of all groundwater and protection of existing and potential drinking water sources and "ecologically vital" waters.

Groundwater pollution problems have been found in many states. Primarily, the main cause is organic chemicals, such as trichloroethylene, 1,1,1-trichloroethane, benzene, perchlorate, gasoline (and gasoline additives such as MTBE), pesticides and soil fumigants, disease-causing organisms, and nitrates. Other sources are industrial and municipal landfills; ponds, pits, and lagoons; waste oils and highway deicing compounds; leaking underground storage tanks and pipelines; accidental spills; illegal dumping; and abandoned oil and gas wells. With 146 million people in the United States dependent on groundwater sources for drinking water, these resources must be protected from physical, chemical, radiological, and microbiological contamination.

Whereas surface water travels at velocities of feet per second, groundwater moves at velocities that range from less than a fraction of a foot per day to several feet per day. Groundwater organic and inorganic chemical contamination may persist for decades or longer and, because of the generally slow rate of movement of groundwater, may go undetected for many years. Factors that influence the movement of groundwater include the type of geological formation and its permeability, the rainfall and the infiltration, and the hydraulic gradient. The slow uniform rate of flow, usually in an elongated plume, provides little opportunity for mixing and dilution, and the usual absence of air in groundwater to decompose or break down the contaminants add to the long-lasting problem usually created. By contrast, dilution, microbial activity, surface tension and attraction to soil particles, and soil adsorptive characteristics might exist that could modify, immobilize, or attenuate the pollutant travel. More attention must be given to the prevention of ground-water pollution and to wellhead protection.

TRAVEL OF POLLUTION THROUGH THE GROUND

Identification of the source of well pollution and tracing the migration of the incriminating contaminant are usually not simple operations. The identification of a contaminant plume and its extent can be truly complex. Comprehensive hydrogeological studies and proper placement and construction of an adequate number of monitoring wells are necessary.

Geophysical methods to identify and investigate the extent and characteristics of groundwater pollution include geomagnetics, electromagnetics, electrical resistivity, ground-probing radar, and photoionization meters. Geomagnetics uses an instrument producing a magnetic field to identify and locate buried metals and subsurface materials that are not in their natural or undisturbed state. Electromagnetics equipment measures the difference in conductivity between buried materials such as the boundaries of contaminated plumes or landfills saturated with leachate and uncontaminated materials. Electrical resistivity measures the resistance a material offers to the passage of an electric current between electric probes, which can be interpreted to identify or determine rock, clay and other materials, porosity, and groundwater limits. Ground-probing radar uses radar energy to penetrate and measure reflection from the water table and subsurface materials. The reflection from the materials varies with depth and the nature of the material, such as sandy soils versus saturated clays. Photoionization meters are used to detect the presence of specific volatile organic compounds such as gasoline, and methane in a landfill, through the use of shallow boreholes. Other detection methods are remote imagery and aerial photography, including infrared.

Sampling for contaminants must be carefully designed and performed. Errors can be introduced: Sampling from an unrepresentative water level in a well, contamination of sampling equipment, and incorrect analysis procedure are some potential sources of error. The characteristics of a pollutant, the subsurface formation, the hydraulic conductivity of the aquifer affected, groundwater slope, rainfall variations, and the presence of geological fractures, faults, and channels make determination of pollution travel and its sampling difficult. Geophysical techniques can help, and great care must be used in determining the number, spacing, location, and depths of sampling wells and screen entry levels. As a rule, monitoring wells and borings will be required to confirm and sample subsurface contamination.

Since the character of soil and rock, quantity of rain, depth of groundwater, rate of groundwater flow, amount and type of pollution, absorption, adsorption, biological degradation, chemical changes, and other factors usually beyond control are variable, one cannot say with certainty through what thickness or distance sewage or other pollutants must pass to be purified. Microbiological pollution travels a short distance through sandy loam or clay, but it will travel indefinite distances through coarse sand and gravel, fissured rock, dried-out cracked clay, or solution channels in limestone. Acidic conditions and lack of organics and certain elements such as iron, manganese, aluminum, and calcium in soil increase the potential of pollution travel. Chemical pollution can travel great distances.

The Public Health Service (PHS) conducted experiments at Fort Caswell, North Carolina, in a sandy soil with groundwater moving slowly through it. The sewage organisms (coliform bacteria) traveled 232 feet, and chemical pollution as indicated by uranin dye traveled 450 feet. The chemical pollution moved in the direction of the groundwater flow largely in the upper portion of the groundwater and persisted for 2-1/2 years. The pollution band did not fan out but became narrower as it moved away from the pollution source. It should be noted that in these tests there was a small draft on the experimental wells and that the soil was a sand of 0.14 mm effective size and 1.8 uniformity coefficient. It should also be noted that, whereas petroleum products tend to float on the surface, halogenated solvents gradually migrate downward.

Studies of pollution travel were made by the University of California using twenty-three 6-inch observation wells and a 12-inch gravel-packed recharge well. Diluted primary sewage was pumped through the 12-inch recharge well into a confined aquifer having an average thickness of 4.4 feet approximately 95 feet below ground surface. The aquifer was described as pea gravel and sand having a permeability of 1900 gal/ft2/day. Its average effective size was 0.56 mm and uniformity coefficient was 6.9. The medium effective size of the aquifer material from 18 wells was 0.36 mm. The maximum distance of pollution travel was 100 feet in the direction of groundwater flow and 63 feet in other directions. It was found that the travel of pollution was affected not by the groundwater velocity but by the organic mat that built up and filtered out organisms, thereby preventing them from entering the aquifer. The extent of the pollution then regressed as the organisms died away and as pollution was filtered out.

Butler, Orlob, and McGauhey made a study of the literature and reported the results of field studies to obtain more information about the underground travel of harmful bacteria and toxic chemicals. The work of other investigators indicated that pollution from dry-pit privies did not extend more than 1 to 5 feet in dry or slightly moist fine soils. However, when pollution was introduced into the underground water, test organisms (Balantidium coli) traveled to wells up to 232 feet away. Chemical pollution was observed to travel 300 to 450 feet, although chromate was reported to have traveled 1,000 feet in 3 years, and other chemical pollution 3 to 5 miles. Leachings from a garbage dump in groundwater reached wells 1,476 feet away, and a 15-year-old dump continued to pollute wells 2,000 feet away. Studies in the Dutch East Indies (Indonesia) report the survival of coliform organisms in soil 2 years after contamination and their extension to a depth of 9 to 13 feet, in decreasing numbers, but increasing again as groundwater was approached. The studies of Butler et al. tend to confirm previous reports and have led the authors to conclude "that the removal of bacteria from liquid percolating through a given depth of soil is inversely proportional to the particle size of the soil."

Knowledge concerning viruses in groundwater is limited, but better methodology for the detection of viruses is improving this situation. Keswick and Gerba reviewed the literature and found 9 instances in which viruses were isolated from drinking water wells and 15 instances in which viruses were isolated from beneath land treatment sites. Sand and gravel did not prevent the travel of viruses long distances in groundwater. However, fine loamy sand over coarse sand and gravel effectively removed viruses. Soil composition, including the presence of clay, is very important in virus removal, as it is in bacteria removal. The movement of viruses through soil and in groundwater requires further study. Helminth eggs and protozoa cysts do not travel great distances through most soils because of their greater size but can travel considerable distances through macropores and crevices. However, nitrate travel in groundwater may be a major inorganic chemical hazard. In addition, organic chemicals are increasingly being found in groundwater. See (1) "Removal of Gasoline, Fuel Oil, and Other Organics in an Aquifer"; (2) "Prevention and Removal of Organic Chemicals"; and (3) "Synthetic Organic Chemicals Removal" in Chapter 2.
(Continues...) Excerpted from Environmental Engineering by Nelson L. Nemerow. Copyright © 2009 by John Wiley & Sons, Ltd. Excerpted by permission of John Wiley & Sons.
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first Published In 1958, Salvato's Environmental Engineering Has Long Been The Definitive Reference For Generations Of Sanitation And Environmental Engineers. Approaching Its Fiftieth Year Of Continual Publication In A Rapidly Changing Field, The Sixth Edition Has Been Fully Reworked And Reorganized Into Three Separate, Succinct Volumes To Adapt To A More Complex And Scientifically Demanding Field With Dozens Of Specializations.

Updated And Reviewed By Leading Experts In The Field, This Revised Edition Offers New Process And Plant Design Examples And Added Coverage Of Such Subjects As Urban And Rural Systems. Stressing The Practicality And Appropriateness Of Treatment, The Sixth Edition Provides Realistic Solutions For The Practicing Public Health Official, Water Treatment Engineer, Plant Operator, And Others In The Domestic And Industrial Waste Treatment Professions.

This Volume, environmental Engineering: Water, Wastewater, Soil And Groundwater Treatment And Remediation, Sixth Edition, Covers:

• Water Treatment

• Water Supply

• Wastewater Treatment