Hazardous Pollutants in Biological Treatment Systems

Fundamentals and a Guide to Experimental Research

Ferhan Çeçen, Ulaş Tezel, Ferhan Çeçen, Ulaş Tezel

• Éditeur: IWA Publishing
• Année: 2017
• ISBN:
  9781780408903
• Sujet: Biological Sciences
• Sous-sujet: Environmental Science

Hazardous pollutants are a growing concern in treatment engineering. In the past, biological treatment was mainly used for the removal of bulk organic matter and the nutrients nitrogen and phosphorus. However, relatively recently the issue of hazardous pollutants, which are present at very low concentrations in wastewaters and waters but are very harmful to both ecosystems and humans, is becoming increasingly important. Today, treatment of hazardous pollutants in the water environment becomes a challenge as the water quality standards become stricter. Hazardous Pollutants in Biological Treatment Systems focuses entirely on the hazardous pollutants present in wastewater and water and gives an elaborate insight into their fate and effects during biological treatment.

Currently, in commercial and industrial products and processes, thousands of chemicals are used that reach water. Many of those chemicals are carcinogens, mutagens, endocrine disruptors and toxicants. Therefore, water containing hazardous pollutants should be treated before discharged to the environment or consumed by humans.

This book first addresses the characteristics, occurrence and origin of hazardous organic and inorganic pollutants. Then, it concentrates on the fate and effects of these pollutants in biological wastewater and drinking water treatment units. It also provides details about analysis of hazardous pollutants, experimental methodologies, computational tools used to assist experiments, evaluation of experimental data and examination of microbial ecology by molecular microbiology and genetic tools.

Hazardous Pollutants in Biological Treatment Systems is an essential resource to the researcher or the practitioner who is already involved with hazardous pollutants and biological processes or intending to do so. The text will also be useful for professionals working in the field of water and wastewater treatment.

© IWA Publishing 2018. Hazardous Pollutants in Biological Treatment Systems: Fundamentals and a Guide to Experimental Research

Ferhan Çeçen, Ulaş Tezel

doi: 10.2166/9781780407715_001

Chapter 1

A guide book to studying the fate and effect of hazardous pollutants in biological treatment systems

Ferhan Çeçen

Boğaziçi University, Institute of Environmental Sciences, 34342 Bebek, Istanbul, TURKEY

Corresponding author: [email protected]

1.1 HAZARDOUS POLLUTANTS AND BIOLOGICAL REMOVAL

The present book deals specifically with the occurrence, effects, removal and monitoring of various types of hazardous pollutants during biological treatment. In that regard, the main focus is on the biological units of drinking water and wastewater treatment plants.

This introductory chapter provides an overview of all of the topics covered within the scope of the book. This chapter also presents the rationale behind the selection of topics and delineates in what aspects the book differs from others. While providing a brief look at the content of each chapter, also suggestions are made for the reader on how to best use the book.

As will be seen throughout this book, hazardous pollutants can be defined in many ways. Commonly, the term “hazardous pollutant” refers to a substance that is likely to threaten the health of humans and the environment upon its release to the environment. Hazardous pollutants may stem from both point- and non-point sources. However, point sources are the primary pathways by which hazardous compounds enter the water environment. Among point sources, the most important one is the discharges made from wastewater treatment plants (WWTPs) (Sathyamoorthy et al. 2013). To avoid the entrance of hazardous pollutants into the water environment, consisting of seas, oceans, lakes, and streams, wastewaters should be adequately treated in WWTPs. Another option to control the release of hazardous substances into the water environment is prevention of pollutant formation, an even more difficult task to accomplish. Since hazardous pollutants reach water bodies, many of them are inevitably found in waters that are extracted for drinking purposes. Thus, the presence of hazardous pollutants is also of concern in drinking water treatment.

1.1.1 Emerging need to control hazardous pollutants

At the beginning of water pollution control, the key issue in wastewater treatment was merely the removal of bulk organic matter and disinfection of treated effluent. Later, nutrient removal too became an important component of biological wastewater treatment. Beginning from the 1970s, hazardous pollutants began to receive attention both in the natural water environment as well as in water and wastewater treatment works. The underlying reason for this was the production of thousands of synthetic organic chemicals (SOCs). A large number of those pollutants were recognized, or at least believed, to have hazardous effects in animals and in humans, such as carcinogenicity and/or mutagenicity. In addition, hazardous inorganic pollutants too have begun to receive attention in recent decades.

Hazardous pollutants can be eliminated or transformed in many ways. However, among all processes the biological ones deserve special attention. Biological processes come into play both in the natural as well the engineered water environment, namely in drinking water and wastewater treatment systems. In both cases biotransformation or biodegradation of hazardous pollutants is possible. If full mineralization (ultimate biodegradation) does not take place, the stable products of transformation can even be more persistent and/or toxic than the parent compounds (Rücker & Kümmerer, 2012). Therefore, today not only the hazardous pollutants in their original form but also their transformation products are studied in biological treatment systems. They are believed to pose risks for ecological systems and human health. While the effects of parent compounds are relatively better understood, there is still a lack of information on generation and effects of transformation products. Particularly, in biological treatment systems it is often difficult to predict and measure transformation products.

Among hazardous pollutants, many organic pollutants such as hormones, pharmaceuticals and personal care products (PPCPs), pesticides, UV filters, fragrances, antimicrobial agents, illicit drugs, brominated flame retardants, industrial products, household products, pesticides, disinfectants and antiseptics, have received special attention in the last few decades (Margot et al. 2015). A recent look at the conferences organized and papers written on the subject, indicates that a significant part of the research on hazardous pollutants centers around the removal of PPCPs from water and wastewater, due to their increased use in recent years. A substantial proportion of PPCPs originate from hospitals, while the rest are discharged domestically (Forrez et al. 2011). PPCPs, as well as many other compounds, cause concern because of their persistent and bioaccumulative properties, and health and ecological impacts. In order to determine such impacts, risks have to be assessed. On the other hand, risk assessment is a comprehensive task involving fields such as chemistry, process technology, toxicology and biology (van Leeuwen & Vermeire, 2007).

Nowadays, a large number of organic hazardous substances enter domestic wastewater treatment plants. These pollutants are often found at extremely low concentrations, namely at the level of a few µg/L or even ng/L. Therefore, they are referred to as micropollutants. If found at those levels a hazardous pollutant may not have an adverse effect on the biological processes going on in a bioreactor. However, if these pollutants are inadequately removed, their effects in the receiving water environment are quite important due to their toxicity, bioaccumulation, long-range transport properties etc. Therefore, in any case, they have to be removed by biological or other means. Also, inorganic hazardous pollutants may affect the treatment systems and then the water environment.

Despite the effects of hazardous pollutants on receiving waters, there is still no consensus about which hazardous substances and discharges need to be regulated and reduced. This arises partly due to the still existing uncertainties about the fate and effects of hazardous pollutants, both in water as well as in wastewater treatment systems, and thereafter in the natural water environment. In some places, bans have been introduced for the use of some specific organics such as alkylphenol ethoxylates with the aim to protect flora and fauna in receiving waters. Yet, regulations have not been developed for the discharge of micropollutants from WWTPs. In few cases limits have been set for specific organics such as benzene which serves as a surrogate parameter for other organic micropollutants. It is believed that upcoming regulations will be increasingly stricter regarding the release of such pollutants (Clouzot et al. 2012).

Similarly, in drinking water treatment systems, hazardous pollutants are encountered at very reduced concentrations, at even lower levels than in wastewater treatment. The hazardous pollutants found in the raw water flowing into a drinking water plant can ste...