**Abstract**

Microcystins (MCs) belong to a family of stable monocyclic heptapeptide compounds responsible for hazardous toxins in drinking water. Although several methods have been applied to remove MCs from drinking water (e.g., activated carbon filtration, ion exchange resins, high-pressure membranes, and electrochemistry), upscaling laboratory experiments to benefit municipal water treatment is still a major challenge. This chapter is a follow-up study designed to test three electrocoagulation (EC) techniques for decomposing MC by UV-ozone purification (laboratory), electrocoagulation (field unit), and coupled UV-ozone-electrocoagulation (municipal treatment). The chemistry and efficiency of the treatments were first examined followed by comparison with activated carbon filtration. Electrocoagulation outperformed activated carbon filtration by nearly 40%. When the laboratory treatments were evaluated at the municipal scale, effectiveness of the technique deteriorated by 10–20% because of UV pulse dissipation, vapor-ion plasma underfunctioning, and limitations of polymer fiber filters. We confirmed previously published studies that pollutant coagulation and MC decomposition are affected by physicochemical factors such as radiation pulse density, electrical polarity, pH, and temperature dynamics. The results have relevant applications in wastewater treatment and chemical recycling.

**Keywords:** microcystins, drinking water, UV-ozone purification, electrocoagulation, municipal, coupled UV-electrocoagulation

### **1. Introduction**

Cyanobacteria (also called cyanotoxins) in drinking water is a global concern because of their hazardous effects on human and animal health [1–3]. Microcystins (MCs) are a common source of cyanotoxins. MCs are produced by a variety of cyanobacteria including *Microcystis spp*, *Anabaena spp*, and *Planktothrix spp*, and to a lesser extent *Dolichospermum spp., Geitlerinema spp., Leptolyngbya spp., Pseudanabaena spp., Synechococcus spp., Spirulina spp., Phormidium spp., Nostoc spp., Oscillatoria spp.,* and *Radiocystis spp*. [4]. *Microcystis aeruginosa* is the most common species of cyanobacteria found in freshwaters around the globe and has been associated with a number of human, livestock, and wildlife poisoning [5, 6].

*M. aeruginosa* commonly produces microcystin-LR (MC-LR) (**Figure 1**) which is the most toxic and most prevalent of the over 100 identified variants [4, 5]. All MCs share a common structure including a cyclic heptapeptide containing three D-amino acids (alanine, glutamic acid, and methylaspartic acid), two "unusual" amino acids (N-methyldehydroalanine and 3-amino-9- methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-dienoic acid (ADDA)), and two variable L-amino acids (X and Z) [7]. MC-LR contains leucine and arginine in the X and Z positions, respectively, and accounts for 99% of total harmful algal blooms [8]. Other less common variants include MCLA, MC-YR, MC-RR, MC-LF, and MC-LW. They are believed to have lower toxicity than MC-LR [6]. MC-LR's biochemistry and toxicity are attributed to the ADDA moiety and its stereochemistry [9, 10]. Mechanistically, MC-LR targets hepatocytes in the liver and enters the cells by active transport aided by anion-transporting polypeptides [11, 12]. Next, the MC-LR binds strongly and irreversibly to serine or threonine protein phosphatases coded as PP1 and PP2A, which subsequently result in enzyme inhibition [13]. Given their importance in cell function and cell regulation, inhibition of PP1 and PP2A can result into hyper-phosphorylation of proteins and cytoskeletal filaments, which can induce apoptosis. MC-LR ingestion may also result in DNA damage, cell proliferation, and possible tumor promotion [12]. Acute toxicity can result in liver inflammation, hemorrhaging, and extensive hepatic bleeding. Death may occur due to liver failure at high or prolonged exposure.

MC-LRs are water-soluble and stable and demonstrate slow natural degradation (half-life = 10 weeks) in polluted water. The molecule is complex and heat-resistant making it toxic even after boiling. Although hard to remove by conventional water

**Figure 1.** *General structure of microcystin-LR.*

*Removal of Microcystins from Drinking Water by Electrocoagulation: Upscaling, Challenges… DOI: http://dx.doi.org/10.5772/intechopen.105751*

treatment, MC can rapidly degrade when exposed to UV radiation with wavelengths close to the absorption peak. Due to the presence of carboxyl, amino, and acylamino groups, MCs have been observed to ionize at temperatures above >40°C and in extreme acid-base media (pH <1.0 or pH >9.0) [9, 14, 15].

The distribution of MC in the US is a serious environmental health problem. Jenssen [16] has reported a wide range of MC concentration (12.5–225.6 μg/L) in multiple US communities. Environmental problems in the Wood County (West Virginia) and Mercer County (Ohio) closely reflect the national situation. Water quality data monitored between 2015 and 2019 by the EPA revealed that MC load in the Grand Lake St. Mary ranged from 0.0 to 79.7 μg/L, compared with the tolerable limit of 1.0 μg/L [17]. Similar data have been reported concerning the Ohio River Valley in West Virginia [16]. As mentioned before, UV exposure and electrocoagulation (EC) are useful methods for MC removal because of the capability to split their C–N bonds using electrical energy [15, 18, 19].

Recently, Folcik and Pillai [14] demonstrated the effectiveness of high-energy electron technology (advanced oxidation-reduction process) in degrading MC pollutants. The technology utilized accelerators to generate highly energetic electrons from regular electricity to create redox species to damage contaminants [20]. Similar examples of radiation technologies employed 60Co gamma rays to inactivate MC multiplication [21–23]. Despite their effectiveness, these technologies are expensive and hi-tech and generally lack practical applications. Nevertheless, one of the techniques that are growing in popularity for MC decomposition is electrocoagulation [15].

Electrocoagulation (EC) employs the principles of electrochemistry for water treatment. It involves sacrificial corrosion of the electrodes (anode) to release active coagulant precursors (e.g., Al3+ or Fe2+) into solution. At the cathode, hydrogen gas evolves from electrolytic reactions. EC equipment can theoretically be scaled for any size and is not too difficult to operate. Recent technical improvements combined with a growing need for small-scale water treatment facilities have amplified interest in EC applications. Nonetheless, only a few studies have focused on the question of scale to demonstrate how laboratory filtration can be upgraded to municipal treatments. In addition, elucidating the key components that control EC production and MC removal efficiency is of paramount interest. Some of the factors that require illumination include current density, electrical polarity, and acid-base equilibria [24]. We hypothesize that a coupled UV-electrocoagulation process will completely remove MC from contaminated drinking water. We also predict that laboratory EC techniques are scalable to municipal purification cognizant that strong water treatment oxidizers like ozone are obtainable from the system's vapor-ion plasma. The aim of this study is to (1) examine the operability and efficiency of cheap laboratory EC units for removing MC from drinking water, (2) test the scalability of laboratory EC filtration to municipal treatments, (3) evaluate the efficiency of the EC results against commercial water filtration (granulated activated carbon), and (4) examine the effects of radiation density, electrical polarity, pH, and temperature on the ionization of MC pollutants. The study will raise questions about electrocoagulation and industrial chemical recycling.

The chapter is structured in the following way. The first part reviews the literature on MC decomposition followed by description of the EC technique including the key components of the electrical units, electrodes activation, and reaction chemistry. The second section discusses the EC methodology followed by data generation, data analysis, and EC scalability. The final part examines the factors controlling EC physics,

including radiation density, electrical polarity, pH, and temperature. The final section also discusses the economy of the new EC method.
