Journal of Ecological Engineering Received: 2019.07.30 Revised: 2019.08.23 Volume 20, Issue 9, October 2019, pages 293–304 Accepted: 2019.09.16 Available online: 2019.09.24 https://doi.org/10.12911/22998993/112557 Wastewater Treatment Methods for Effluents from the Confectionery Industry – an Overview Magdalena Zajda1, Urszula Aleksander-Kwaterczak1* 1 AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection; al. A. Mickiewicza 30, 30-059 Krakow, Poland * Corresponding author’s e-mail: [email protected] ABSTRACT Wastewater from the confectionery industry is characterized by daily and seasonal variability of composition and quantity which adversely affects the process of their disposal. Confectionery plants discharge about 300-500 3m per month of technological wastewater. Sewage from the confectionery industry belongs to biologically degrad- able. It is characterized by high values of chemical oxygen demand (COD) and biological oxygen demand (BOD). The article reviews various methods used to treat wastewater from the confectionery industry. Attention was paid to the applicability of a particular method, its advantages and disadvantages and the costs of implementa- tion. The technology of industrial wastewater treatment uses both mechanical and physicochemical methods as well as biological ones. Techniques of sewage treatment usually consist of several stages which use different processes. Low-cost materials such as natural minerals, agricultural waste, industrial waste, biosorbents, and others contribute to the improvement of aerobic sewage conditions. The main weakness of typical sewage treat- ment plants is their large area, high investment, and exploitation costs. Therefore, a good solution may be the use of the membrane biological reactor which combines the classical technique of activated sludge and filtration on micro-filtering membranes. Keywords: confectionery industry, wastewater treatment, biological oxygen demand, chemical oxygen demand, low-cost material INTRODUCTION high concentration of phosphorus and nitrogen (Demirel et al. 2005; Qasim and Mane 2013) and The confectionery industry is one of the most causes pollution of waters which could be used as widespread and important industries around the a source of drinking water. The pollution of wa- world. It manufactures sweets including choco- ter caused by sewage input is a serious threat for late confectionery and gum products which are people and animals (Elhassadi 2008). characterized by significant amounts of sugar Industrial waste consisting of a lot amount of and sugar substitutes, cocoa, fats, emulsifiers, organic compounds uses the oxygen dissolved in and flavours used in the production process (Ed- water to biochemical disintegration of these sub- wards 2000; El-kalyoubi et al. 2011; García-Mo- stances. The excessive oxygen usage by sewage rales et al. 2018). may result in its total reduction in receiving wa- The development of different industry branch- ter. This influences on generating anaerobic con- es has significantly improved people’s qual- ditions which cause the extinction of aerobe and ity of life in many aspects. However, industrial blocks the oxygen process of sewage self-clean- plants developing so numerously have started to ing. Water de-oxidation has also a bad influence emit a lot of water pollution (Próba and Wolny on organisms living in the aquatic environment 2013). In many cases, sewage is discharged (Gromiec et al. 2014). into rivers without any purification (Ntuli et al. Water protection from industrial pollu- 2011) which causes eutrophication, due to the tions is one of the basic elements of sustainable 293 Journal of Ecological Engineering Vol. 20(9), 2019 development. In order to achieve this, it is nec- biological oxygen demand (BOD) (Krzanowski et essary to purify the industrial wastewater more al. 2008). The COD index has usually values with- efficiently and to change the technologies to in the limits of 1000-12000 mg O2/L, while BOD5 more friendly to the environment (Rajman 2007; up to 500-8000 mg O2/L (Table 1). The organic Qasim and Mane 2013). A good method of con- substances that are contained in wastewater are trolling water pollution is the monitoring of in- mainly sugars, fats, and dyes (Colic et al. 2009; dustrial plants that discharge sewage directly to Esparza-Soto et al. 2013; García-Morales et al. municipal channels. However, the task is often 2018; Rucka et al. 2012; Qasim and Mane 2013). too expensive especially for largely industrialized Confectionery sewage often contains solutions for regions (Ntuli et al. 2011). Quite often the costs washing and disinfecting agents too, which can that a production plant has to pay for the emission cause changing the pH value and increasing the of poor quality sewage are very high. Therefore, content of nitrogen and phosphorus compounds factories are more and more often using different (Krzanowski et al. 2008). methods of sewage pretreatment. The work reviews various methods used to treat wastewater from the confectionery indus- WASTEWATER TREATMENT METHODS try. It was paid attention to the possibilities of using a particular method and its advantages and The treatment of wastewater is a relatively disadvantages. modern practice. The first mechanical and biolog- ical processes designed to treat municipal waste- water emerged early by the end of the 19th century CHARACTERISTIC OF WASTEWATER (Environmental Protection Agency 1997). FROM THE CONFECTIONERY INDUSTRY The technology of industrial wastewater treat- ment uses both mechanical and physicochemical The main source of sewage in the confection- methods as well as biological ones (Figure 1) ery industry is the cleaning process of the installa- (Bhargava 2016). tion, so the amount of sewage generated depends on its frequency. For this reason, it is character- Mechanical treatment ized by daily and seasonal variations in the com- position and the quantity. This affects the process Mechanical wastewater treatment, this so- of its disposal. The confectionery plants discharge called first stage of purification, are intended about 300-500 m3 per month of technological to eliminate larger floating and dragged solids, wastewater (Rucka et al. 2012). This sewage is granular particles with a diameter greater than biodegradable and it consists primarily of organic 0.1 mm, and easily falling suspensions, oils and compounds and suspensions which affects the high fats. This is achieved through the use of grates values of chemical oxygen demand (COD) and and screens that trap and separate solid objects Table 1. The main properties of sewage from the exemplary confectionery plants BOD COD EC pH NH +-N P total Kind of industry 4 Literature [mg O2/L] [mg O2/L] [μS/cm] - [mg/L] [mg/L] Candy manufacturing plant 8000 2500 ‒ ‒ ‒ ‒ Colic et al. (2009) in Mexico Chocolate manufacturing García-Morales ‒ 3608 750 7.4 ‒ ‒ industry in Mexico et al. (2018) Confectionery plants in 5400 10,996 633 4.1 28.5 13.2 Rucka et al. (2014) Poland Food industries (dairy Qasim and Mane effluent, sweet-snacks and 442-523 8960-11,900 794-1082 5.6-7.1 89-120 78-157 (2013) ice-cream), India Food processing industry Vanerkar et al. 6860 11,220 ‒ 4.1-4.3 ‒ 3.2 in India (2013) Sugar industry, Ethiopia ‒ 3682 ‒ 5.5 ‒ 5.9 Sahu (2017) Confectionery factory – ‒ 20,025 680 3.8 ‒ ‒ Ozgun et al. (2012) sugar line, Turkey Sugar industry, Pakistan 3132 12,211 ‒ 9.5 ‒ ‒ Khan et al. (2003) Note: ‒ not determined. 294 Journal of Ecological Engineering Vol. 20(9), 2019 Fig. 1. Wastewater treatment methods from the bulk wastewater. At this stage, pro- The ideal adsorbents should be solids with a cesses such as filtration, drainage, sedimentation large surface area, porosity, inertness, and good and flotation take place. As a result, the content physical and chemical properties (Paprowicz of organic compounds in wastewater can be re- 1990; Parande et al. 2009). As low-cost adsor- duced by a few percents (Bartkiewicz and Um- bents natural minerals (bentonite, kaolinite, zeo- iejewska 2010). lites, silica beads), agricultural waste (eggshells, corn cobs, chicken feathers, rice husks, coconut Physicochemical treatment shells), industrial by-products, biosorbents (chi- tosan, peat, biomass) and others (e.g. starch, cy- Sorption clodextrin, cotton) were tested (Al-Jlil 2009; Ar- The process of sorption includes two phe- iffin et al. 2017; Carvalho et al. 2011; Parande et nomena. The first of them is adsorption, which al. 2009). It was found that also such elements involves the attachment of molecules on the sur- as wool, sawdust, cocoa shell, sugar beet pulp, face of a solid or liquid. The second is the absorp- distillery sludge or maple saw dust can be effec- tion consisting of the sorption of one substance tive in metals reduction and the improvement of by another forming any continuous phase. Meth- aerobic conditions in wastewater. Furthermore, ods using the adsorption process is considered as metakaolin and carbon made from dates nuts one of the most competitive because they are not and tamarinds in the condition of neutral pH can complicated and do not require high operating significantly improve the oxygen conditions in temperature (Hashemian et al. 2014). wastewater with a high content of organic com- Activated carbon is a material that adsorbs pounds (Parande et al. 2009). It was also demon- organic compounds very well (Dakhil 2013). This strated that a perfect absorbent is an active carbon is due to its large surface area, porosity and resist- produced from almond shells and orange peels ance to chemical and thermal changes (El-Dars et wastes (Hashemian et al. 2014). al. 2014). For this reason, it is the most versatile It was observed that active carbon produced adsorbent used in the wastewater treatment pro- by activation with phosphoric acid (H3PO4) from cess. It reduces BOD and COD values by more olive stones has a very well developed pore struc- than 90% (Devi et al. 2008; Nayl et al. 2017; Sa- ture, which will result in the high level of pollu- nou et al.