Phosphorus and Nitrogen Removal from Municipal Wastewater

Principles and Practice, Second Edition

RichardI. Sedlak, Richard I. Sedlak

• Publisher: Routledge
• Year: 2018
• Print ISBN:
  9780873716833
• eBook ISBN:
  9781351424936
• Topic: Technology & Engineering
• Subtopic: Environmental Science
• Index: Technology & Engineering

This valuable new book offers practical guidance regarding the design and operation of systems for reducing effluent nitrogen and phosphorus. The principles of nitrogen and phosphorus removal are discussed, including sources of nitrogen and phosphorus in wastewater, removal options, nitrogen and phosphorus transformations in treatment, process selection, and treatment. The book also covers the design and operation of nitrogen and phosphorus removal systems, including system options, system design, facility design, facility costs, and operation. Practical case studies are provided as examples of successful system implementations that may be able to help you decide what will work best in your plant.

Chapter 1

Introduction

As the approach of removing phosphorus from municipal wastewaters to control nuisance aquatic plant growth enters its third decade of application in the United States, two significant trends can be observed. First, it is a well established approach to ameliorate water quality problems that will be increasingly applied over the next decade and beyond. For example, twenty percent of the total U.S. treatment capacity is expected to be capable of removing phosphorus in the year 2000, a percentage that is twice as great as in 1982(1).

Second, localized water quality problems can be expected to lead to lower and lower effluent phosphorus limitations. Historically, effluents limits of 1 or 2 mg total phosphorus (TP) per liter have been broadly applied in regions of the U.S.A., such as in the Great Lakes Drainage Basin (1 mg/L) and the Lower Susquehanna River Basin (2 mg/L). However, localized water quality conditions are leading to lower effluent phosphorus limits in some areas. One area where this has been the case for a number of years is the lower Potomac River Basin where municipal plants must meet discharge limits that are lower than 0.2 mg TP/L.

Concerns over nitrogen compounds have been primarily over ammonia toxicity to aquatic organisms, which has resulted in nitrification requirements being implemented more broadly than even phosphorus removal. Like for phosphorus, the extent of nitrification is expected to increase. It is anticipated that 27% of the total U.S.A. sewage flow will be treated for nitrification by the year 2000(1).

In contrast to phosphorus, requirements for nitrogen removal from municipal wastewaters historically have been applied on a limited basis in situations where nitrogen reductions are needed to correct localized water quality problems. However, an increasing trend in the future toward nitrogen removal requirements can be expected due to at least a couple of factors. First, nitrogen removal is now being considered on a broad-scale basis to reduce the availability of this nutrient to aquatic plants. For example, removal of nitrogen at municipal wastewater treatment plants is being considered throughout the Chesapeake Bay Drainage Basin. Second, broad-scale removal of nitrogen is being considered in areas where there is concern over the fate of nitrogen compounds in ground water drinking supplies that depend on recharge using municipal wastewaters. The proportion of the total U.S.A. sewage flow treated for removal of nitrogen is expected to double from 1982 levels by the year 2000, to approximately 2%(1).

As urban populations and, therefore, sewage flows increase and the accomplishments of current control programs become more apparent, consideration may be given in the future to more stringent municipal effluent limits for phosphorus and nitrogen to address local water quality problems.

All of the steps to date to control municipal phosphorus and nitrogen have not come without some considerable effort and cost. Nor will future reductions be effortless. However, programs to control nutrients over the past two decades have encouraged the development not only in the U.S.A. but elsewhere in the world of many treatment technologies for phosphorus and nitrogen removal. While dependable treatment technologies, such as chemical treatment for phosphorus removal, have been successfully utilized over these past two decades, improved understanding of the principles of the process has led to more efficient use of the approach. In addition, improved understanding of the mechanisms behind the biological removal of phosphorus will lead to broader and more efficient application of this approach. Similar comments can be made regarding the technologies for removal of nitrogen.

This document summarizes the available technologies for removing phosphorus and nitrogen from municipal sewage, with emphasis on those that are expected to see prominent use either because of their treatment capabilities or their ease and cost of operation, or both. The information is presented in two sequential blocks: one on the chemical, biological, and physical principles behind the available treatment technologies; a second on the design and operation of processes and systems based on these principles.

The information presented is based on available literature, as well as the experiences of the authors. It is presented in a format and with appropriate detail to assist those involved in the early stages of addressing the need to initiate nutrient removal at a facility or evaluating the feasibility of achieving lower effluent nutrient limits, such as personnel in government agencies, consulting and design engineers, and plant operators. Where appropriate the reader is directed to documents containing more detailed information on the design and operation of these types of facilities.

1.1 References

1.    Barth, E. F. Phosphorus control and nitrification processes for municipal wastewater. USA/USSR Bilateral Agreement on Water Pollution Control, 1985.

Chapter 2

Principles of Biological and Physical/Chemical Nitrogen Removal

2.1 Introduction

Nitrogen exists in many forms because of the high number of oxidation states it can assume. In ammonium and organic nitrogen compounds, which are the forms most closely associated with plants and animals, its oxidation state is -3. At the other extreme, when nitrogen is in the nitrate form, its oxidation state is +5. In the environment, changes from one oxidation state to another can be accomplished biologically by living organisms. The most prevalent forms of nitrogen in wastewaters and, therefore, those which may require treatment, are organic, ammonium and nitrate nitrogen.

The presence of nitrogen in a wastewater discharge can be undesirable for several reasons: as free ammonia it is toxic to fish and many other aquatic organisms; as ammonium ion or ammonia it is an oxygen-consuming compound which will deplete the dissolved oxygen in receiving water; in all forms, nitrogen can be available as a nutrient to aquatic plants and consequently contribute to eutrophication; as the nitrate ion it is a potential public health hazard in water consumed by infants. Depending upon local circumstances, removal of all forms of nitrogen or just ammonium may be required. Both objectives can be achieved economically in biological treatment systems.

2.2 Sources of Nitrogen in Wastewater

Municipal wastewater of predominantly domestic origin contains nitrogen in the organic and ammonium forms. These are primarily waste products originating from protein metabolism in the human body. In fresh sewage about 60 percent of the nitrogen is in the organic form and 40 percent in the ammonium form. Bacterial decomposition of proteinaceous matter and hydrolysis of urea transform organic nitrogen to the ammonium form. Normally, very little (less than 1 percent) of the nitrog...

Table of contents

• Cover
• Title Page
• Copyright Page
• Table of Contents
• 1 Introduction
• 2 Principles of Biological and Physical/Chemical Nitrogen Removal
• 3 Design and Operation of Biological Nitrogen Removal Facilities
• 4 Principles of Chemical Phosphate Removal
• 5 Design and Operation of Chemical Phosphorus Removal Facilities
• 6 Principles of Biological Phosphorus Removal
• 7 Design and Operation of Biological Phosphorus Removal Facilities
• 8 Case Studies in Biological Phosphorus Removal
• Index