**2. Materials and methods**

#### **2.1. Tomato wastewater industry**

Tomato-processing wastewaters are typical high strength wastewater generated from the food canning industry. Composite wastewater samples from tomato manufacturing company were collected and analyzed for parameters considered necessary for wastewater characterization and system design for a year. Characteristics of the Tomato wastewater industry showed that 73.4 % of the TSS, was volatile organics; and 64% of the COD was insoluble form. Soluble NH4 –N constituted 74% of TN. The tomato processing industry wastewater were used as substrates for the combined system consisting of AH reactor as a pretreatment and PTF as a post-treatment unit (Fig. 1).

#### **2.2. Anaerobic hybrid (AH) reactor**

5 l AH reactor was designed and manufactured from polyvinyl chloride (PVC) as described earlier by Tawfik et al., (2011) and illustrated in Fig. 1. The AH reactor consisted of a sludge blanket at the bottom, and floating polyurethane carriers at the top to overcome washout of sludge from the reactor. The surface area of polyurethane carriers in the AH reactor was 0.57m2. NaHCO3 was added to adjust the influent pH in the range of 6–7. The seed sludge was taken from an up-flow anaerobic sludge blanket (UASB) reactor treating juice industry wastewater. The sludge is typically flocculent with mixed liquor suspended solids (MLSS) of 16.8 g/l, mixed liquor volatile suspended solids (MLVSS) of 10.8 g/l and VSS/TSS ratio of 0.64. Three liters of the sludge was pumped into the AH reactor as an inoculum.

**Figure 1.** PTF module coupled with AH reactor for treatment of tomato industry wastewater

#### **2.3. Polyurethane trickling filter (PTF) reactor**

356 Polyurethane

total suspended solids (TSS) and nitrogen for discharge into drainage canals. Therefore, post-treatment is needed. Trickling filter (TF) is one of the aerobic biological treatment systems that are widely used for post-treatment of anaerobically pretreated effluent. However, the TF still has some drawbacks such as difficulty in maintenance of appropriate biofilm thickness under limitation of oxygen supply and biofilm detachment from the packing materials. In this investigation polyurethane trickling filter (PTF) was proposed. It has several advantages compared to conventional TF. In TF of which micro-organisms attach themselves only to a media surface creating a biological filter or slime layer, but in PTF module, the micro-organisms are retained outside and inside the polyurethane media which create long sludge residence time (SRT>100 days) (Tawfik et al., 2006) and consequently, achieve a complete nitrification and produce a very low amount of sludge (Tawfik et al., 2006). Once again, PTF brings the following advantages compared to conventional TF, the amount of active biomass brought in contact with the wastewater is very high and the biological process is very fast, thus very short retention time is needed which gives small plants with no investment cost (Tawfik et al., 2010). The process is in contrast to conventional TF which needs a very low OLR to achieve a nitrification process (Tawfik et al.,2011; Chernicharo &Nascimento, 2001). Moreover, it is easy to enlarge the capacity of PTF system in case the flow and/or the organic load would increase in the future. The objectives of this investigation are to 1. assess the efficiency of a combined system consisting of AH reactor and PTF for the treatment of tomato industry wastewater at different HRTs and OLRs with emphasis on the COD fractions (CODtotal; CODsoluble and CODparticulate); TSS and total nitrogen (TN) removal. In addition, the mechanism for the

removal COD, TSS and nitrification efficiency along the height of PTF is investigated.

Tomato-processing wastewaters are typical high strength wastewater generated from the food canning industry. Composite wastewater samples from tomato manufacturing company were collected and analyzed for parameters considered necessary for wastewater characterization and system design for a year. Characteristics of the Tomato wastewater industry showed that 73.4 % of the TSS, was volatile organics; and 64% of the COD was insoluble form. Soluble NH4 –N constituted 74% of TN. The tomato processing industry wastewater were used as substrates for the combined system consisting of AH reactor as a

5 l AH reactor was designed and manufactured from polyvinyl chloride (PVC) as described earlier by Tawfik et al., (2011) and illustrated in Fig. 1. The AH reactor consisted of a sludge blanket at the bottom, and floating polyurethane carriers at the top to overcome washout of sludge from the reactor. The surface area of polyurethane carriers in the AH reactor was

**2. Materials and methods** 

**2.1. Tomato wastewater industry**

**2.2. Anaerobic hybrid (AH) reactor**

pretreatment and PTF as a post-treatment unit (Fig. 1).

The PTF is packed with porous polyurethane foam (pore size= 0.63 mm) with relatively high specific surface area (256 m2/m3) to increase both the biofilm mass content and the removal efficiency of the reactor. The PTF module used in this study, consisted of three segments connected vertically in series. The polyurethane represents 15% of the total reactor volume (23l) (Fig. 1). Polyurethane media was warped with perforated polypropylene material (0.5 cm) to avoid clogging of the media and facilitate the air penetration inside the packing material. The PTF was equipped with 276 pieces each 40 mm height and 20 mm in diameter with 90% of porosity. The reactor was operated without inoculums. The distributer is situated on the top of the reactor and operated at 18 rpm for equal distribution of wastewater over the packing material. The air was naturally diffused to the reactor via three windows along the reactor height. There is no need for aeration as well as no backwashing.
