**1. Introduction**

Canned foods were well known and widely used for feeding the armies since the mid-eighteenth century. Nowadays, they play a crucial role in the everyday nutrition of everyone all over the globe, where they provide food with good quality that can last for a long time compared with fresh food. The canned food production industry, as any other industry, includes material processing, storing, and transportation. These activities lead to waste and emission generation and can affect the environment negatively if not well planned and applied. These negative effects might include air and water pollution and soil contamination. Of the major pollutants generated by this industry, the organic pollutants are very crucial [1].

In general, food processing from raw materials requires large volumes of highgrade water, which will become wastewater after usage. In particular, it requires a large volume of potable water for several usages, e.g. raw materials cleaning, fluming, blanching, pasteurizing, processing equipment cleaning, and cooling of the final products. These vast usages require the enforcement of quality criteria for the water used in each application; the best quality usage often requires independent treatment to assure complete freedom from odor and taste and to ensure uniform conditions [1]. The wastewater effluents from this industry are characterized by their large volumes. On average, some 10–20 m3 wastewaters are produced per tonne of products. The precise characteristics of these wastewaters are highly dependent on the performed processes during the canned food production, i.e. the process of vegetable washing leads to the generation of wastewaters with high loads of some dissolved organics, and particulate matter [2].

The organic content in the wastewater generated as a result of the operation of different processes in the food canning industries is characterized by high concentrations of biodegradable contaminants and variable pH levels. When an environmental reservoir, e.g. a stream or waterway, receives these wastewater effluents, the organic pollutants will consume some of the dissolved oxygen (DO) that exists in the reservoir during their stabilization. This will reduce considerably the DO to levels below that required for the sustainability of lives of the aquatic organisms. The extent of pollution caused by these effluents can be characterized based on the plant capacity, the utilized process, and the characteristics of the raw materials. In this respect, it is beneficial to categorize the plant capacity in terms of population, where seasonal plants are likely to generate waste loads equivalent to 15,000 to 25,000 people, and large plants generate loads up to 250,000 people. The processing of fruit and vegetables is one of the sources of wastewaters, which contain organic matters. Fruit and vegetable canning companies generate wastewaters with high levels of biochemical oxygen demand (BOD), total solid (TS), and suspended solids (SS) [1]. This chapter aims to introduce the available technologies for secondary wastewater treatment that are widely investigated to prevent and control pollution from the food industry. In this respect, the features of the aerobic and anaerobic biological treatment technologies are summarized. Then, an overview of the uncertainty management in biological treatment plants is provided.

### **2. Cannery wastewater treatment**

Due to the nature of the food industry, the preparatory and operational processes of the raw animals, vegetables, and fruits into edible products do not include the application of chemicals. Subsequently, the organic maters in most of the cannery wastewater effluents are best treated using biological treatment, where these matters are rarely present toxicant or inhibitory compounds in their composition. Yet in some operations, e.g. sterilizing and cleaning the equipment, chemicals are used. In particular, disinfectants and caustic soda are used at the end of the processed batch. These effluents could be characterized as short-time concentrated discharges. They may cause shock loads in the wastewater treatment plants that are not designed to deal with these effluents. In this case, the use of equalization unit can achieve acceptable flow equalization and pH adjustment and dilute the high concentration to a nominal concentration that allows safe operation for the biological treatment unit [3].

### **3. Aerobic treatment of cannery wastewaters**

Aerobic wastewater treatment processes could be applied using several technologies, i.e. pond and lagoon-based treatments; surface and spray aeration; oxidation ditches; trickling filters; septic or aerobic tanks; activated sludge; and aerobic digestion. In this section, sequencing batch reactor (SBR), activated sludge (AS), rotating biological contactor (RBC), and aerobic lagoons (AELs) for treating food processing wastewater are discussed.

#### **3.1 Sequencing batch reactor (SBR)**

In general, SBR is a fill-and-draw activated sludge system for wastewater treatment. In that system, wastewater effluent is added to a single batch reactor, where treatment is achieved by removing undesirable components, and then, the effluent is discharged. In the same single batch reactor, equalization, aeration, and clarification are conducted.

The formation of granules in aerobic conditions has been possible and appears as a promising technique for treating high-strength or highly toxic wastewaters. It appeared that aerobic granules were successfully cultivated only in SBR. The cyclic operation of SBR consisted of influent filling, aeration, settling, and effluent removal [4].

The development of aerobic granular sludge to achieve simultaneous removal of COD, phosphorous (P), and nitrogen (N) from saline fish-canning wastewater was investigated by Campo [5]. In that work, a 1.6-L SBR with a hydraulic retention time (HRT) of 0.25 d and a volumetric exchange ratio (VER) of 50% was used. The wastewater fed to the SBR was collected from a fish-canning factory located in the south of Galicia (Spain). The SBR was operated in 3-hour cycles comprising 60-min anaerobic feeding, 112-min aeration, 7–1-min settling, and 1–7-min effluent discharge. The salt concentration was approximately 10.4 ± 0.8 g NaCl/l, and the applied organic loading rate (OLR) equals 5.4 ± 1.9 kg COD/(m3 d). Under these conditions, aerobic granules were detected after operational time equals 34 days. Some filamentous bacteria were detected on the surface of the aggregates. The granular biomass has a volatile suspended solids (VSS) concentration of 1.34 gVSS/l, density near 11.5 gVSS/l granule, and mean diameter of 1.35 mm. After 41 days of operation, fluffy-flocculent suspension was formed in the presence of the granules. This behavior was attributed to the salinity and the respectively high fraction of slowly biodegradable COD in the influent (35% of total COD). The study reported good removal efficiencies of soluble COD nearly equal to 80%. The phosphorus and ammonium were mainly concluded to be removed to cover the minimum metabolic demand of heterotrophic bacteria. The study indicated that the enrichment of the biomass with slow growing autotrophic and phosphorus-accumulating bacteria in a saline environment requires a longer operational time [5].
