**1. Introduction**

As one of the dominant industries in Georgia, USA, the pulp and paper industries consume huge amounts of fresh water and a wide variety of chemicals during pulp production processes. A significant amount of water and these chemicals are released as high pollutant load with intense color effluent into surface water bodies [1]. Pulp and paper mill effluents (PPMEs) transport high concentrations of organic/inorganic pollutants and color compounds like lignocellulosic compounds, tannins, hemicelluloses, pectin, resin acids, unsaturated fatty acids, carboxylic acid, and other substances [2]. These untreated effluents are responsible for increasing the levels of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total organic carbon (TOC), adsorbable organic halides (AOXs), toxic contaminants, and heavy metals in the water ecosystem [3]. Therefore, PPMEs must be treated before they are discharged into receiving water bodies.

Physical treatment can efficiently remove 80% of suspended solids (SS) from pulp mill effluents (PMEs) [4]; Aerobic lagoon and anaerobic treatment studies showed potentially removing 50% color and 60% COD from PMEs [4, 5]. However, these fungal treatment studies are still ongoing and in the early stage of industrial implementation [6]. The coloration of receiving water bodies from PMEs causes negative impacts including an unpleasing esthetic appearance, reduction of dissolved oxygen (DO) level, and reduction of sunlight transmission into bodies of water which may adversely affect aquatic life. Additionally, insufficient sunlight reduces photosynthetic activity, therefore, making it difficult to remove organic pollutants and causing an increase of water/wastewater treatment costs downstream [7, 8]. Hence, tertiary treatment is essential for the further treatment of PMEs.

Adsorption, a proven and widely used treatment process, removes a variety of contaminants from industrial wastewater. Activated carbon, the most common adsorbent, is widely used to remove contaminants from industrial wastewater for a long time [9, 10]. However, the high production costs of activated carbon have motivated researchers to explore alternative low-cost adsorbents like coal fly ash (CFA), rice husk ash (RHA), bagasse fly ash (BFA), etc. industrial for wastewater treatment.

Energy sector is another dominant industry in Georgia, USA. It produced 6.1 million tons of CFA as byproducts in 2011 and 60% of CFA were disposed of in ash ponds. Investigating other beneficial uses of CFA in environmental engineering is necessary. The results from our Batch Studies have shown that CFA can effectively remove color from PME as a low-cost adsorbent [11]. However, these results were achieved in a batch operation using the powdered CFA samples, which are rarely used in a column in practice for a continuous operation due to their low permeability.

Therefore, the objectives of this study were to explore the cost-effective immobilization processes of powdered CFAs with water and addition of binders, to produce the CFAs beads with strength and high adsorption capacity for color removal from PME, and to use these CFA beads in column studies to remove color from the PME under a continuous operation.

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

#### **2.1 Coal fly ash (CFA)**

Three (3) raw CFA samples were obtained from three individual coal-based power plants units of Georgia Power Company and labeled as CFAs #1 - #3. The first one was Class "C" subbituminous ash, whereas the last two were Class "F" bituminous ashes. These CFAs were stored in plastic containers at room temperature (20 10°C) in the Water and Environmental Research Lab (WERL) at Georgia Southern University (GSU) for further study. The chemical composition of CFA#2 is summarized in **Table 1**.

#### **2.2 Pulp mill effluent**

For this study, three (3) biologically treated secondary PMEs samples were collected from three different pulp mill factories from surrounding areas in Georgia, USA. They were labeled as PMEs #1 - #3, respectively. All these PMEs were collected from secondary clarified effluent outlets. These PMEs were stored in plastic container in a refrigerator at temperature of 4 1°C in the WERL at GSU for further study. The primary properties of these PMEs are summarized in **Table 2**.

*Immobilization of Powdered Coal Fly Ashes (CFAs) into CFA Beads and Column Studies… DOI: http://dx.doi.org/10.5772/intechopen.94293*


#### **Table 1.**

*The chemical composition of CFA#2.*


**Table 2.**

*The primary properties of the three (3) PMEs.*

#### **2.3 Chemical reagent**

For immobilization process, N type hydrated lime was collected from the Material Laboratory at GSU.

#### **2.4 Immobilization process**

The immobilization study of powdered CFAs was started by operating the key equipment of pelletizer (DP-14 Agglo-Miser Disc Pelletizer supplied by Mars Mineral) with each of the three CFA samples and water only without adding any binders. Multiple immobilizing parameters, such as RPM and the vertical angle of the pan of the pelletizer, and the ratio of CFA sample to water, as well as optimum curing conditions on humidity and duration, were investigated. The optimal rotational speed of pelletizer and vertical angle of the pan were found 32 RPM and 45 degree, respectively, and they were maintained the same during the whole immobilization process. For each batch, 2500 gm of CFA powder was pelletized by adding hydrated lime or Class "C" type CFA directly while water was added using spraying bottle. After palletization, the fresh pellets had to be cured with thin layer covered by wet cloth at room temperature (20 1°C) in the WERL at GSU for two weeks and exposed to atmosphere for air dry for one week before being used in column studies (12).
