**1. Introduction**

Sewage sludge is a non-homogeneous material constituting of a combination of various compounds including organic and inorganic materials as well as microorganisms, and moisture [1, 2]. It is counted up as the major by-product resulted from treatment of wastewater. The sludge undesirable content of heavy metals, synthetic organic compounds and pathogenic bacterial and other microorganisms represents a major harmful environmental risk. Therefore, disposal process of this by-product surely lead to unwelcomed environmental impacts including human beings health threats and the possibility of atmospheric polluting, as well as water and soil resources contaminating [1, 3]. The remarkable high phosphorus,

nitrogen and potassium nutrients content imparts sewage sludge a property of being used as agricultural fertilizer however a series harmful substances content oppose this beneficial application [4–6]. Hence the main aim of sewage sludge treatment is to eliminate sludge unfavorable contents while to retain sludge nutrients. The primary two steps in the treatment processes of sewage sludge are thickening and dewatering. The first one is aiming to thickened sludge to lower solid percent, while the other one reduces the water content by (centrifugation, filtration, and/or evaporation) in order to reduce transportation costs of disposal, or to improve suitability for advanced processing [7, 8]. On the other hand, digestion (anaerobic and aerobic), incineration, and composting aim to diminish the organic matter content and the amount of harmful microorganisms existing in the residue matter [9–15].

The high heavy metal content in the sewage sludge represents another major obstacle against sludge utilization. The non-biodegradability nature, unlike organic contaminants, leads to accumulation of heavy metals in the biota, which involves a health risk and an environmental worry. Although metabolism of living organism needs metal ions in order to carry out many metabolic pathways, higher concentrations can cause expected acute as well as chronic toxicity. Therefore, rigorous parameters have been approved for release of various metal ions in wastewaters to evade health risk and environmental contamination. Various chemical, physical, and biological treatment methods such as chemical precipitation, adsorption, membrane filtration, ion-exchange, electrochemical treatment and microorganisms have been established for removing metal ions from water and wastewaters [16–29]. Among these wide scope of heavy metal treatment methods, utilizing of chelating agents has demonstrated a pronounced impact in eliminating of harmful metals [30, 31]. Challenges of metal ions removal can be represented in that metal ions are adsorbed on soil, so it shows resistance to be removed upon washing by surface and ground water moreover the actual low water solubility of some transition metals hydroxides. The remarkable metal binding capabilities enables chelating agents to overcome these challenges [32–36]. The most commonly ligand, Ethylenediamine-tetraacetic acid (EDTA), a hexadentate ligand, has the ability to bind most of heavy metals forming very stable complexes [37–41]. However the problem of non-biodegradability is the main drawback of EDTA utilization, as the degradation of EDTA results in formation of a stable organic pollutant (3- ketopiperazine-N,N-diacetate) [42]. The bio-degradable isomer S,S-ethylenediamine disuccinic acid (S,S-EDDS) has been proposed as a likely alternative chelating agent [43, 44], however its ability to metal ions is inferior and special pH conditions should be taken into consideration as the influential pH range is narrower [45].

In this study a novel organic Schiff base chelator derived from hydroxybenzylidene succinohydrazide (HBSH) has been successfully synthesized and characterized by elemental analysis, 1 H-NMR as well as infrared spectroscopy. The ability of this novel Schiff base to decontaminate semi-solid sewage has been investigated. The utilization of the treated sludge has been also tested as a plant fertilizers. The influence of raw as well as treated sludge on the growth and heavy metal content in radish plant have been also investigated.

### **2. Material and methods**

### **2.1 Instrumentation and measurement**

The C, H and N content in the obtained compounds was analyzed at the Microanalytical Laboratory, Cairo University, Egypt. Metal ion content was determined *Perspective Chapter: Removal of Heavy Metals and Salmonella Pathogens from Sewage Sludge… DOI: http://dx.doi.org/10.5772/intechopen.109224*

using Standard analytical methods [46–48]. Jasco FT/IR 300E Fourier transform infrared spectrophotometer covering the range 400–4000 cm−1 was used to record FT-IR spectra of the ligand and its metal complexes using KBr discs. 1 HNMR spectrum was obtained on a JEOL EX-270 MHz FT-NMR spectrometer in d6-DMSO as solvent. Where the chemical shifts were determined relative to the solvent peaks. All metal concentrations were detected using Perkin Elmer ICP (ICP-MS-1).

### **2.2 Preparation of the Schiff base (HBSH)**

The Schiff base, (HBSH) was prepared by refluxing (4 gm, 0.022 mole) of 2,3 dihydroxy succcinohydrazide in ethanol with (4.8 ml) of salicylaldehyde (1: 2 molar ratio), for 5 hours at 80°C (**Figures 1** and **2**). The formed yellow precipitate was left to cool to room temperature, then filtered off and dried under vacuum over anhydrous CaCl2. [C18H26N4O10]Yield: 75%, Color: yellow. Elemental Anal. Calc.: C, 47.16; H, 5.72; N, 12.22. Found: C, 46.98; H, 5.39; N, 12.10. IR, (KBr, cm-1): 3650,3665,3620,3180 <sup>υ</sup> (OH/H2O), 3320-2730 <sup>υ</sup> (H-bonding) 1705, 1690 <sup>υ</sup> (C=O), 1318,1272<sup>υ</sup> (COH), 1630,1622 <sup>υ</sup> (C=N).

### **2.3 Settled sludge volume (SV30)**

The sludge used in this study was collected from the sewage outcome of the aeration tank of Al kharry waste-water plant, El-Behira Governorate, Egypt. Settled Sludge Volume was estimated using reported standard method [49, 50]. In briefly, 1 L of the sludge sample (raw or treated) was places in settling column and the solid content was uniformly distributed by inverting the covered cylinder for three times,

### **Figure 1.**

*Preparation of the Schiff base 2,3-dihydroxy-N,N4-bis(2-hydroxybenzylidene) succinohydrazide (HBSH).*

**Figure 2.** *Variation in TSS concentrations along raw and treated sewage at 0.8gL−1.*

then stirred using stirring rod. The suspension is kept under stirring throughout the experiment. The volume occupied by the suspension was determined for 30 minutes at 2 minutes intervals. The same procedures were carried out in presences of different concentration of the succinohydrazide Schiff base (0.8, 1.6, 2.4) g/L.

### **2.4 Sludge and radish digestion**

Digestion of raw sludge, treated sludge as well as radish plant was carried out by well suspension of 1gm of the dry sample in 100 ml of distilled water. Three milliliter of conc. HNO3, and the mixture was evaporated cautiously to 4 ml, then 5 ml of conc. HNO3 (15.8 M) was added and refluxed for 1 hour. The mixture was cooled then solution of (15 ml of HCl (11.65 M) + 15 ml H2O) was added heated again for 15 minutes then cooled. Finally 100 ml of distilled water was added, the mixture was filtered and the heavy metal was estimated on ICP (ICP-MS-1) - Germany [50].
