Systems Based on Physical-Chemical Processes

High strength waste streams, namely rejected water from a wastewater treatment plant, livestock slurry, and agro-food wastewater, are characterized by its high organic matter and nutrient content which favours processes aiming to recover energy and nutrients, instead of removing them. In this regard physical-chemical processes are suitable technologies to attain these objectives. Among others, stripping coupled with absorption, struvite precipitation, membrane separation, and vacuum evaporation, are all physical-chemical processes aiming to concentrate nutrients in a stream that can later be reused as fertilizer. In this chapter the main physical-chemical processes will be defined and described in terms of the objective of each process technique, their theoretical fundamentals, environmental effects (air, water and soil emissions, resource depletion), technical indicators (efficiencies, energy consumption, etc.), and by-product characteristics.

Nutrients Pollution in Water Bodies

The pollution of water bodies by an excess of nutrients (N and P) is a worldwide problem with effects on the human health, ecosystems status, climate change, etc. To face with this important issue different regulations were promulgated by the countries, sometimes based on the results from international conventions and programmes. In this chapter, a review of the laws and regulations that affect the discharge of nitrogen and phosphorus is addressed, focused in the case of Europe and the United States. Finally, a brief explanation about international initiatives was performed to understand the global framework concerning nutrients pollution.

Aerobic Granular Sludge

Aerobic Granular Sludge (AGS) has been successfully applied for carbon, nitrogen and phosphorous removal from wastewaters, in a single tank, reducing the space and energy requirements. This is especially beneficial for, often space restricted, industrial facilities. Moreover, AGS holds a promise for the toxic pollutants removal, due to its layered and compact structure and the bacteria embedding in a protective extracellular polymeric matrix. These outstanding features contribute to AGS tolerance to toxicity and stability. Strategies available to deal with toxic compounds, namely granulation with effluents containing toxics and bioaugmentation, are addressed here. Different applications for the toxics/micropollutants removal through biosorption and/or biodegradation are presented, illustrating the technology versatility. The anthropogenic substances effects on system performance and bacterial populations established within AGS are also addressed. Combination of contaminants removal to allow water discharge, and simultaneous valuable products recovery are presented as final remark.

Chemical and Biological Processes for Nutrients Removal and Recovery

This chapter gives an overview on the main technologies for nutrient removal from industrial wastewater by focusing on principles and operational parameters of real applications. A plethora of technologies can achieve the nutrients removal from wastewater depending mainly on their concentration and forms; however, biological nitrification and denitrification and chemical precipitation are the most common processes used today to remove nitrogen and phosphorus, respectively. Stripping, adsorption and membrane based processes for nutrients recovery can be economically viable only when nitrogen concentration is higher than 1.5-2 gN/L. On the other hand, phosphorus recovery should always be pursued and struvite crystalization is the most common option that should be evaluated together with biological phosphorus accumulation in sludge or plants for the following post-processing and valorization.

Biogeochemical Cycles of Nitrogen and Phosphorus

The study of biogeochemical cycles is important to understand the circulation of elements through aquatic, aerial and terrestrial ecosystems. Among others, N and P are considered as the limiting nutrients that determine the productivity of organisms. Since human activity is increasing its influence over these cycles at a global scale, it is important to analyze the implications of anthropogenic variations in order to detect the sources and try to prevent or reduce their impact. Moreover, not only the increasing or diminished concentration of nitrogen and phosphorus in nature by human resource exploitations is needed to account today. As metals play a crucial role in the dynamics of these essential elements, their presence in the environment also requires a significant attention.

Modelling and Control of Nitrogen and Phosphorus Removing Systems

A wide variety of technologies addressing nutrient removal in wastewater treatment have been developed in the latest years. In order to be able to design, manage, operate, optimise and benchmark these novel technologies with potentially existing standard technologies, detailed modelling of nutrient removal becomes essential. Nutrient removal is prominently considered, with different degrees of complexity, in the commonly used Activated Sludge Models (ASM). However, the description of nutrient-related compounds in these standard models is not sufficiently detailed for novel and not so novel technologies. Furthermore, the environmental evaluation of a process, which includes an estimation of the greenhouse gas release, would require a more complex process to represent nitrogen removal. This chapter reviews the current state of nutrient removal modelling, with special focus on the needs created by emerging technologies in nitrogen and phosphorus removal, paying special attention to the objectives that must be evaluated for each technology.

Fundamentals of the Biological Processes for Nitrogen Removal

In this chapter the fundamental aspects involved in biological treatment processes applied for the removal of nitrogen from wastewaters are described. A comprehensive review of the literature is provided including kinetic, microbiological and biochemical aspects of nitrification, denitrification and anammox, as well as key operational parameters affecting the processes. This information is relevant for designing wastewater treatment processes applied for the removal of nitrogen from wastewaters. The information is also essential for predicting and controlling the performance of these treatment processes.

Anammox Process

Application of anammox based processes is nowadays an efficient way to remove nitrogen from wastewaters, being good alternative to the conventional nitrification-denitrification process. This chapter reviews the possible configurations to apply the anammox process, being special attention to the previous partial nitritation, necessary to obtain the adequate substrates for anammox bacteria. Furthermore a description of the main technologies developed and patented by different companies was performed, with focus on the advantages and bottlenecks of them. These technologies are classified in the chapter based on the type of biomass: suspended, granular and biofilm. Also a review is presented for the industrial applications (food industry, agricultural wastes, landfill leachates, electronic industry, etc.), taking into account full scale experiences and laboratory results, as well as microbiology aspects respect to the anammox bacteria genera involved. Finally the possibility to couple nitrogen removal, by anammox, with phosphorus recovery, by struvite precipitation, is also evaluated.

Constructed Wetlands for Industrial Wastewater Treatment and Removal of Nutrients

Constructed Wetlands (CWs) are low-cost and sustainable systems for wastewater treatment. Traditionally they have been used for urban and domestic wastewater treatment, but in the last two decades, the applications for industrial wastewater treatment increased due to the evolution of the technology and the extended research on the field. Nowadays, CWs have been applied to the treatment of different kind of wastewaters as such as refinery and petrochemical industry effluents, food industry effluents including abattoir, dairy, meat, fruit and vegetables processing industries, distillery and winery effluents, pulp and paper, textile, tannery, aquaculture, steel and mixed industrial effluents. In this chapter, the authors present the main types of CWs, explain how they work and the expected performances, and describe the principal applications of CWs for industrial wastewater treatment with particular attention to suspended solids, organic matter and nutrient removal. A review of these applications as well as some case studies will be discussed.

Autotrophic Denitrification Processes

Effluents coming from anaerobic digesters are characterized by a COD/N ratio between 2 and 10, high ammonia NH4+ concentrations about 500 mg/L and a temperature range of 25-35 ºC. To remove nitrogen from these effluents biological processes as the autotrophic denitrification with sulfur compounds, hydrogen or methane can be applied. The main goal of this chapter is to describe and evaluate the use of these processes from an economic point of view. The methanotrophic denitrification is the cheapest alternative to remove nitrate from effluents with low COD/N ratios.