Treatment of Fish-Processing Wastewater Using Polyelectrolyte and Palm Anguish

Abstract

Fish-process wastewater industries are a significant source of environmental pollutions and biohazard to humans and other living organisms due to suspended organics, phosphorus, and nitrate that causes environmental damage. In this study, the treatment of two types of fish wastewater was examined by applying chemical and physical methods. The chemical treatments using positive polyelectrolyte with a concentration of 25 ppm reduced the turbidity of fish wastewater by 50%; conductivity was reduced by 50% and pH was reduced from 8 to 7.2. Meanwhile, using negative polyelectrolyte and mixed polymers reduced the turbidity of fish wastewater by 30%. For applying natural material as a physical adsorbent, several natural materials were examined: ocimum leaves, Boswellia sacra leaves, Al-Shakher leaves, tephrosia leaves, neem leaves, mentha leaves, jand peel, neem wood, ocimum fruit, olive fruit peel, and palm anguish for the treatment of the fish wastewater. The initial tests indicated that the best material was palm anguish. FTIR, SEM, and EDS were used for the characterization of palm anguish. The selected material was treated with 1 M of NaOH solution. Different bed heights (10, 20, and 30 cm) of Palm anguish were applied. The results showed 80% and 85% reduction in the turbidity in both types of fish wastewater, especially with a bed height of 30 cm of the fish wastewater treated with NaOH, respectively. Notably, this study distinguishes itself by utilizing polyacrylamide flocculants of varying densities and by employing palm anguish as a natural adsorbent, which can sufficiently improve the treatment of fish-processing wastewater.

1. Introduction

The worldwide production of fish and seafood has increased steadily over the last decade, which is expected to continue [1]. The fish industries consume large amounts of water for washing and cleaning the fish raw materials and processing, consequently resulting in equally large quantities of wastewater [2]. Fish processing increases the amount of the generated wastewater by local and fish farms industries, which are associated with blood, oil, salts, suspended organic compounds, and solid materials. In principle, these pollutants make the treatment of fish-processing wastewater very difficult [3]. To prevent environmental damage, fish-processing wastewater requires treatment before disposal. The normal performance of treatment processes of fish wastewater within the wastewater treatment plants includes physicochemical treatments as primary units for the removal of oils and the particulate matter followed by biological reactors (oxidation basin) for the removal of dissolved organic materials with the aid of activated sludge [4]. The conventional treatment using activated sludge systems are widely employed to treat both industrial and urban wastewater due to their adaptability and flexible operations.

There are many wastewater problems that are faced day-by-day worldwide. One of the current solutions is traditional sewage wastewater treatment [5]. Wastewater treatment plants are facing many difficulties for the treatment of fish processing, which is heavily contaminated wastewater, resulting in a negative impact on the biological treatment and discharge of inadequately treated wastewater may cause unacceptable environmental issues. The different types of fish wastewater in terms of quality and quantity are not adequate due to high liquid pollutants; the waste loading from the fish-processing effluents is the major potential source of hazards to the coastline and seashore environments [6]. This litter carries different types of bacteria, which are a source of many diseases affecting humans and water supply. It also mainly modifies the chemical and biological properties of the receiving ecosystem in the wastewater treatment plant [7,8]. It is one of the most common problems around the world being scrutinized due to the many dangers it has diverged and resulted from. Certainly, international studies and statistics estimated that the global wastewater production is 359.4 × 10⁹ m³/day, of which only 63% is collected but 52% is treated [9]. Almost 30% of global wastewater is produced from fish canning and other fish productions [6].

To shed light on the Sultanate of Oman as a part of the global sewerage systems, studies have indicated that in 2000, the production of wastewater was about 37.446 × 10⁶ m³/year. At the same time, the government in Oman is ramping up investment in the treatment of wastewater and the possibility of reused capacity. Modern technology for sewage collection and disposal infrastructures are established, which covers more than 98% of urban and rural communities as of 2018. In 2019, more than 68 sewage treatment plants produce about 97 × 10⁶ m³/year of treated wastewater. Sixty-one percent of the treated wastewater is used for agriculture and injection in costa aquifers [10]. There are currently more than 402 treatment plants in the Sultanate, which came in the text of Ministerial Law No. 31/2002, in which it was decided to establish a treatment and management system for sewage collection on 17 December 2002. Subsequently, all stations were included in one company under the name Haya Water company. By the end of 2011, the sewage stations collected about 84,144 m³/day. The sewage volume is expected to rise by 2025 and may reach 327,853 m³/day [11]. Based on the issue of sewage water around the world and the Sultanate of Oman in particular, as well as the statistics based on this, fish water is one of the major wastes, whose percentage is increasing dramatically and rapidly. The reason behind this is that fish products constitute the largest sectors of global food trade, which is estimated at 78% of the marine products offered to global trade competition.

According to data from the National Institute of Statistics, with prepared and canned fish [12,13], the essential environmental trouble of the fisheries industries is the high consumption of water and the maximum productivity of the organic components, oil, and salt contents that flow into the wastewater. Fish processing in many manufacturing industries produces massive amounts of wastewater. The production of this wastewater typically consists of producing unwanted parts from the fish such as: properly washing the excess salt, blood, scales, head and entrails, which are not typically used as food. The operations of washing, cleaning, cooling, packing, and packaging fish contribute to an increase in the volume of production of liquid waste, which generates massive quantities of oils, grease, organic materials, salts, etc. In this manner, it is difficult to treat due to its high content of these wastes and its subjection to pretreatment in the sewage system and further treatment in the sewerage plant itself. Most countries have tended to put in place measures about this specific type of pollution that fish factories produce to reduce the volume of liquid waste, eliminate it, reduce it, or value the hazardous materials coming from it so that the water efficiency is increased to obtain water with quality requirements allowed to be used and re-used. The treatment of pollutants and recovery of some materials by industrial processes are in line with economic and environmental sustainability [7,14].

The study of Chowdhury et al. [15] stated that there is a specific need to put in place rigid regulations for effluent water day after day because rational biological treatment is the best solution. The water consumed in the manufacture and processing of fish has become excessive in wastewater, which has shifted it into a primary concern all over the world. The anaerobic flow processes of the Sludge Blanket Reactor (UASB), the Anaerobic Filter (AF), and the Anaerobic Fluid Bed Reactor (AFB), contributed to the achievement of rapid rates organic element removal and the production of biogases, which were estimated between 80–90%. In addition to these processes, biological conductors, drip filters, and lakes are considered to be the most suitable medium for the removal of organic elements. The most efficient option for treating wastewater from fish involved anaerobic drilling, followed directly by aerobic drilling.

Beltran–Heredia et al. [16] applied coagulant agent for treating wastewater. The new coagulant is based on tannin by using Acacia mearnsii de Wild tannin extract, NH₄Cl, and formaldehyde. This coagulant (cationic coagulant) is affected by temperature and tannin–NH₄Cl ratio. An ideal combination was found for a ratio of NH₄Cl and temperature for each system, 24.9 °C and 2 g/g for dye removal and 36.4 °C and 1.87 g/g for surfactant elimination. The best circumstances were combined to create a combination coagulant that tested on wastewater and surface river water. Its efficacy has been confirmed.

Thakur and Choubey [17] presented a study using a natural coagulant (tannin). Natural sources of tannins have been found, including the leaves, fruits, barks, roots, and wood of trees. A substance was extracted and ground from the bark of acacia catechu. To assess coagulant rates and doses, turbidity measurements and the pH of surface water samples were assessed before and after the jar-test. In addition, we determined the total suspended solids using the gravimetric method. Acacia catechu powder is an effective natural coagulant as it can remove turbidity by 91%. In addition, it removes total dissolved solids by 57.3%.

Mseddia et al. [18] carried out experimental works to reduce the organic load of saltwater from fish industries by optimizing the use of coagulation and flocculation. The results of this study show that the treatment achieved a reduction of 60% of COD and 84% of turbidity. The next step in this process is to treat the effluent by inoculating it with the halophilic consortium. This method involves inoculating the effluent with high concentrations of salts. The results of this study revealed that the combination of biological and physicochemical treatment resulted in high-performance degradation.

De melo and Naval [19] carried out a study aiming to find a different technological method that could be efficient and possibly reusable. For the fish-processing industry, there are many difficulties faced in the treatment, such as the high concentration of organic materials, suspended solids, and the non-uniform configuration of the compound. Until this is done, treatment systems are used to scan the sewage and check for pH, TSS, BOD, COD, TN and TP, oils, and greases. The comparison found results in concentrations where multiple processes were combined using advanced techniques in treatment, when the goal is reusing or recycling, it achieves the values specified by the industrial reuse criteria. The work of De melo and Naval [19] was to remove important characteristic factors after analytical comparisons were made between the different sewage treatment technologies that involved two different systems: conventional and advanced. There was also a focus on physical treatment (combining sediment/decant and float/sediment) and chemical treatment, chemical flocculate, ozone process, and oxidation process that are adsorbed and advanced. Biochemical treatment included active sludge, filter/anaerobic, bioreactor, and aerobic reactor. For further reuse or recycling, the treated sewage uses one or more of these technologies and comprises quality that determines the regulations of industrial recycling.

Tatiane et al. [20] presented the treatment of fish processing using the coagulation/flocculation (C/F) process, by using an organic coagulant (Tanfloc SH) and inorganic coagulant (FeCl₃) in the presence of copolymer. These experiments determined that the effectiveness of Tanfloc SH is the same as that of FeCl₃ in treatment fish processing, but natural coagulant is more viable because of the disadvantages of acidification of final supernatant and chemical residues left by inorganic coagulant. The effectiveness of both coagulants was determined by measured color, turbidity removals, and COD removal; the COD removal data suggest that the C/F process performed well.

Hong Anh et al. [21] stated that the considerable increase in wastewater after the use of seawater in the manufacture and treatment of fish and shellfish led to a rapid boom in aquaculture projects, and the annual production in 2018 reached about 94.6-million tons. Total suspended solids (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD), and modern nitrogen (TN) are identified as the most standard components produced in fish wastewater. To follow the environmental regulations, a giant treatment may be required before discharging due to the unmoderated concentrations of nutrients, natural compounds, and total nitrogen that this water contains. The pH ranges in treating fish effluents with condensate production from 9 to 10. Thus, pH is used as a characterization factor for the emission of ammonia compounds in effluent pollution. The be-around TSS was 635 mg for each liter. In addition, it was established in one more report that it contributes to an augment in BOD and COD plus total nitrogen levels. The total of one hundred solids was about 10–30% suspended in the water streaming as of fish wastewater proper to the attendance of proteins and fats. The dissolvable solids vary between 150 and 1100 mg or, even in some cases, 22,910 mg in fish-processing vegetation. The organic composites that are produced from the treatment of fish wastewater hold significant percentages of BOD and COD. It was determined that the ratios of both differ in fish-processing plants and range from about (From 1.1:1 to 3:1). Its levels should be reduced by 83 and 66%, respectively, for BOD and COD. In addition, the results showed that the percent of nitrogen and phosphorous concentrations vary according to the quality and quantity of fish treated in the wastewater. This may be due to the amounts of protein contained, while the percentage of nitrogen reaches between 15–20%. This elevated level of ammonia is explained by the presence of slime and blood in sewage streams. In addition,, phosphorous has very massive effects, which are produced by processing and cleaning fish, with a volume between 13–47 mg/L.

Recently, Priya et al. [22] carried out a study for the immobilized thermo-stable enzyme treated with fish-processing wastewater. The treated wastewater was characterized by various parameters, such as pH, COD, lipid, and temperature. The optimized operating conditions were found to be 45 °C and 4 h. The effluent including hydrolyzed fish oil was then treated in a fluidized immobilized carbon catalytic oxidation reactor. When compared to the raw water properties, the concentration of each parameter gradually decreases. This is due to the presence of rice as a catalyst that controls the physical and chemical parameters.

The objectives of the work are the treatment of fish processing water using positive and negative polyelectrolyte (polyacrylamides-SFN) as flocculated. In addition, the treatment of fish-processing water using palm anguish (untreated and treated with NaOH) as a natural adsorbent was investigated.

2. Materials and Methods

Solutions of 1000 ppm of different polyacrylamides (positive and negative) were prepared by dissolving 1 g of each in one liter of distilled water and thoroughly mixed using a magnetic stirrer for 8 h. For the treatment of fish wastewater, three different concentrations were used: 25, 50, and 75 mL.

For the selection of the best natural biomaterials as adsorbent, several natural materials were selected: ocimum leaves, Boswellia sacra leaves, Al-Shakher leaves, tephrosia leaves, neem leaves, mentha leaves, jand peel, neem wood, ocimum fruit, olive fruit peel, and palm anguish. Each of them was dried for 2 days, then grinded and mixed with fish wastewater. Ten grams from materials were added to 500 mL of fish wastewater in each beaker of Jar tester. The solutions were mixed at 200 rpm for two min, then at 30 rpm for 30 min. Samples were collected from each beaker after 1 h for turbidity analysis. The results are presented in

Table 1. Natural biomaterial.

Plant Sample	Turbidity (NTU)
Ocimum leaves	533
Boswellia Sacra leaves	289
Al-Shakher leaves	313
Tephrosia leaves	510
Neem leaves	500
Mentha leaves	319
Jand peel	90.8
Neem Wood	91.4
Ocimum fruit	228
Olive fruit peel	198
Palm anguish	61.5

. Images of settled treated fish wastewater are shown in Figure 1. It can be seen that palm anguish was the best biomaterial for adsorption treatment, as turbidity was reduced by 90%.

Two types of experimental tests were carried out for the treatment of fish-processing wastewater.

• Chemical treatment using polyelectrolyte.
• Physical treatment using palm anguish.

Two samples of fish-processing wastewater were collected from the Nizwa fish market with different characteristics, as shown in

Table 2. Characteristics of samples of fish wastewater.

Sample	Turbidity	pH	Conductivity (ms/cm)
1	44.7	7.88	767
2	79.3	7.95	755

.

Using the two types of polyelectrolytes as flocculants for the treatment of fish-processing wastewater, Jar tester was used for mixing different concentrations of polyelectrolytes with 1 L of fish-processing wastewater filled in six beakers, each beaker with 1 L and adding a different volume of positive and negative polyelectrolytes into each beaker (25, 50 and 75 mL). The solutions were mixed at 200 rpm for 2 min for proper mixing and then mixed at 30 rpm for 30 min to allow for flocculation. The solution of each beaker was poured into a graduated cylinder and, during settling, samples of supernatant were collected, each 30 min for analysis (turbidity, pH, conductivity).

For natural adsorption process, palm anguish was grinded and then sieved; the selected grinded size was 500–710 µm. To enhance the adsorption capacity, 83 g of the grinded palm anguish was soaked in 2 L of 1 N NaOH for 24 h. Then, the anguish was filtered and washed with distilled water several times until the pH was reduced to about 8. The solid was dried in an electrical oven at 60 °C for 24 h.

The adsorption process using treated and non-treated palm anguish with NaOH was performed in a cylindrical column with a height of 100 cm and a diameter of 2.8 cm. The experimental photo and schematic diagram are depicted in Figure 2. Bed height of palm anguish was used (10 cm, 20 cm, and 30 cm). The fish wastewater was pumped through the column using a dozing pump (china-YZ1516 x-Baoding Chuangrui Precision Pump Co., Ltd., Baoding, China) with a flow rate ranging from 0.0064 L/min to 0.021 L/min. Samples from the outlet were collected every 5 min until anguish was saturated. During the experimental work, the selected flow rate of fish wastewater through the beds was 0.0142 L/min using a peristaltic pump at a speed of 20 rpm.

To identify the functional groups of palm anguish (treated and non-treated with NaOH), which are responsible for the adsorption of dye molecules, Fourier Transform Infrared Spectroscopy (FTIR) spectrum of palm anguish was taken. The FTIR device is available at Daris laboratory at the University of Nizwa. Figure 3 shows the FTIR spectra of palm anguish. The spectrum reveals the presence of new functional group for the palm anguish that was treated with NaOH, the following chemical characterization: a strong absorption band at 3400 cm⁻¹ shows the presence of hydroxyl groups as part of cellulose structure [23]. The bands observed in the region between 2000 cm⁻¹ and 3000 cm⁻¹ were attributed to $C\equiv C$ symmetrical stretching of pyrone groups and C=O of carboxylic groups. The positions of the most characteristic bands for lignin in the region are 1585 cm⁻¹ for aromatic skeletal vibrations, 1415 cm⁻¹ for C-H deformation, 1315 cm⁻¹ for syringyl ring plus guaiacyl ring, and 1112 cm⁻¹ for aromatic skeletal vibrations. A FTIR peak at 1030 reflects either S=O stretching of sulfoxide functional group or CO–O–CO stretching of anhydride. The characteristic band 1028 cm⁻¹ originates from the C–O stretching vibration of -C–OH group. The band at 555 cm⁻¹ arises from b–glucosidic linkage [23].

Scanning electron micrographs were obtained on scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) at Daris laboratory at the University of Nizwa. The surface morphology of the palm anguish was depicted in Figure 4. The SEM images indicate rough surface morphology of the materials before and after washing with NaOH, respectively, several large pores were clearly found on the surface of base activated material. This shows that the activation with NaOH is more effective in forming pores on the surface of the raw anguish sample, leading to a large adsorption surface area and porous structure. Similar finding was observed by Hameed and Daud [24]. These pores provided a good surface for waste effluents to be trapped and adsorbed. In respect to EDS measurement, it can be seen that both samples (raw and washed with NaOH) have large carbon contents: 75% for the raw sample and 56% after washing with NaOH.

3. Results and Discussion

3.1. Results of Treated Fish Wastewater Using Polyelectrolyte

The positive and negative polyelectrolytes were used at different concentrations (25 mL, 50 mL, 75 mL) for the treatment of two types of fish-processing wastewaters with different turbidity (Samples 1 and 2). The results of turbidity, pH, and conductivities are shown in Figure 5, Figure 6 and Figure 7 for the treatment of Sample 1 and Figure 8, Figure 9 and Figure 10 for the treatment of Sample 2. The results of using mixed polymers (positive and negative) are shown in Figure 11. The results indicated the effectiveness of using positive polyelectrolyte on the turbidity of the treated fish wastewater. The turbidity was reduced by 50% when adding 25 ppm on Sample 1 (see Figure 5a), while an excessive addition of polyelectrolyte has less of an effect on turbidity due to repulsion between polyelectrolyte particles of similar charges as the concentration increased. Turbidity was reduced by 30% when adding 50 ppm, but there was not much change in turbidity when adding 75 mL. For the use of the negative polyelectrolyte, turbidity was reduced by 25% by adding 25 ppm (see Figure 5b), while an excessive addition of polymer has not much effect on turbidity. This behaviour may be referred to the repulsion between negative charges of the polymer particles and the inorganic phosphate $\left({\mathrm{P}\mathrm{O}}_3^{-}\right)$ and Nitrate $\left({\mathrm{N}\mathrm{O}}_2^{-}\right)$ that are present in the wastewater. It can be observed that a better reduction of turbidity when using the positive polyelectrolyte may refer to the attraction between the polymer and inorganic and organic phosphate-suspended materials. Hence, they lead to the precipitation of these materials and reduce turbidity.

A little drop in pH value for the treatment using both polymers, as shown in Figure 6, can be observed. This may be due to a reduction in carboxylic ions that are attracted to the positive polyelectrolyte. Similarly, a reduction of positively charged carbonyl groups used negative polyelectrolytes. In addition, the results showed that the conductivity (Figure 7) was reduced by almost 50% when using both negative and positive polymers. This reduction could be due to the precipitation of dissolved metal contents using polyelectrolytes with opposite charges and orthophosphate and calcium bicarbonate that reacted both positive polyelectrolyte and negative polyelectrolyte, respectively.

The results of turbidity of treated Sample 2 of fish wastewater (Figure 8) showed a reduction by 50% using positive polyelectrolytes with all concentrations (25, 50, and 75 mL), while the turbidity was reduced by 50% only with using 25 mL of negative polyelectrolyte; no such change in turbidity was used with other amounts. This may be due to the repulsion between negative polyelectrolyte with the negatively charged inorganic phosphate $\left({\mathrm{P}\mathrm{O}}_3^{-}\right)$ and Nitrate $\left({\mathrm{N}\mathrm{O}}_2^{-}\right)$ present in wastewater. Comparisons between the treatment of Samples 1 and 2 using polyelectrolytes indicates the effect of the polymer and the larger impact on samples with larger turbidity due to the large chance of attraction between polymer and particles of pollutants present in the wastewater.

A little drop in pH value from 7.96 to 7.3 can be observed, as shown in Figure 9. The reduction in pH may be due to a reduction in carboxylic ions, which reacted with positive polyelectrolyte, as well as a reduction of positively charged carbonyl groups using negative polyelectrolyte. Like that of Sample 1, the conductivity (Figure 10) was reduced by almost 50% when using both negative and positive polymers. This reduction could be due to the precipitation of dissolved metal contents using polyelectrolytes with opposite charges and orthophosphate and calcium bicarbonate that reacted with both positive polyelectrolyte and negative polyelectrolyte, respectively.

The use of mixed positive and negative polymers reduced turbidity by 50% with mixed polymer concentrations of 50 and 75 mL, as shown in Figure 11a. This reduction in turbidity at higher concentrations refers to the increase in the amount of positive polyelectrolyte, like that of treated Samples 1 and 2.

A little drop in pH value from 8.2 to 7.1 can be observed, as shown in Figure 11b. The reduction in pH may be due to the reduction in carboxylic ions, which reacted with positive polyelectrolytes as well as the reduction of positively charge carbonyl groups using negative polyelectrolytes. Like that of Sample 1, the conductivity in Figure 10c was reduced by almost 40% when using both negative and positive polymers. This reduction could be due to the precipitation of dissolved metal contents using polyelectrolytes with opposite charges and orthophosphate and calcium bicarbonate that reacted with both positive polyelectrolytes and negative polyelectrolytes, respectively.

3.2. Results of Treated Fish Wastewater Using Natural Adsorption on Sample 1

Palm anguish was used as a natural adsorbent for the treatment of fish wastewater, which was washed with NaOH and used as an adsorbent for the treatment of fish-processing wastewater. Three different bed heights were used: 10, 20, and 30 cm. The flow rate of fish wastewater through the beds was 0.0142 L/min using a peristaltic pump at speed of 20 rpm. The results are depicted in Figure 12.

It can be seen when using a bed of treated palm anguish with NaOH that using a bed height of 30 cm concluded with a better result for reducing turbidity compared to other bed heights of 10 and 20 cm (Figure 12a). The break time using the three bed heights (10, 20, and 30 cm) are 170, 250, and 370 min, respectively. It is clear that the break time point of the bed with 30 cm is much longer than the others. The bed height of 30 cm provides an opportunity for the adsorption process of pollutants present in the fish water. The palm anguish is washed with NaOH, which in turn expands the pores so that the adsorption process of pollutants takes place more and prevents them from falling with the outputs.

The results of using untreated palm anguish NaOH are depicted in Figure 12b. It can be observed that using bed heights of 20 and 30 cm resulted in almost similar and better outcomes compared to those obtained results using a bed height of 10 cm. Both beds 20 and 30 cm have a break time of 250 and 300 min, respectively, while 10 cm has a break time of 230 min.

The pH and conductivity results from the adsorption process showed a reduction of 0.8 in pH level and 42% in conductivity of fish wastewater, as depicted in

Table 3. Results of the pH and conductivity of treated fish wastewater using pal anguish.

Palm Anguish	Initial pH	Final pH	Initial Conductivity (ms/cm)	Final Conductivity (ms/cm)
Treated with NaOH	7.88	7.2	767	322
Non-treated	7.88	7.35	767	354

. The reduction in conductivity refers to the adsorption of ion metals onto the surface of palm anguish, especially with that treated with NaOH due to the availability of pore surface area.

4. Conclusions

The follow conclusions are drawn from this work:

∘

Using palm anguish as natural adsorbent can sufficiency improve the treatment of fish-processing wastewater.

∘

Chemical treatment using positive polyelectrolytes resulted in an acceptable reduction in the turbidity of fish wastewater reaching 50%. Conductivity was reduced by 50% and pH was reduced from 8 to 7.

∘

The results of physical adsorption using raw and washed palm anguish with NaOH resulted in a sufficient reduction in the turbidity reaching 85% and a break time of 370 min, especially with a bed height of 30 cm.

∘

The use of natural adsorption reduced conductivity by 42%.

∘

The results showed that the treatment of fish wastewater using physical adsorption is more sufficient compared to that using chemical treatment.

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SEM and EDS analysis showed that the palm anguish has a large carbon content, and the pore sizes were increased after washing with NaOH.