Comparison of the physical profile of Klayton and LECA as media for aquaponics

Jover Nuevaespana1 and Jonathan R. Matias2 1AquaOrganika, 2Poseidon Sciences R&D, Miagao, Iloilo 5023 Philippines 1URL: www.aquaorganika.com 2URL: www.poseidonsciences.com

Email: poseidonnova@aol.com

Abstract

The physical profile of the growing media is a requirement to measure the efficiency of bio filtration of fish waste in the aquaponics system. Klayton and Light Expanded Clay Aggregate (LECA), both ceramic based growing media, were evaluated based on physical profile. Klayton has higher water absorption per surface area as compared to LECA. High surface area provides more space for the growth of nitrifying bacteria.

Keywords: aquaponics, nitrification, bio filtration, Klayton, LECA, aquaponics growing media, physical profile of Klayton, physical profile of LECA

http://www.aquaorganika.com/http://www.poseidonsciences.com/mailto:poseidonnova@aol.com

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Introduction

Klayton and Light Expanded Clay Aggregate (LECA) are growing media in the soil-less culture of plants in an aquaponics system. The growing media serves as the bio-filter for the cleaning up of the fish waste. Bio-filtration is defined in aquaponics as a pollution control technique using living material to capture and biologically degrade the ammonia in the waste water [1]. Nitrification is the biological oxidation of ammonia with oxygen, then into ammonium, then into nitrite followed by the oxidation of these nitrites into nitrates [1]. Nitrifying bacteria, the performers of nitrification process, are the living organisms responsible for the conversion of ammonia rich fish wastewater into clean nutrient rich water for plants.

Currently, LECA (Fig. 1) is a material in popular use to create surface for nitrifying bacteria. [2]. Hydroton, the popular LECA, has been discontinued in 2012 after the manufacturing company, Okotau Easy Green , closed their LECA factory in Germany due to quality issues. Many other new companies quickly came to the market to fill the void. LECA is now manufactured in more than 20 countries under different brand names. Some countries which produce aggregate with almost the same industrial method as Okotau are Italy, Denmark, Switzerland, Norway, Germany, Finland, Portugal, U.K, and Iran using the same brand of LECA; Russia, Poland,

Sweden, and China, with the brand of Keramzite; South Africa, with the brand of Argex; and Spain, with the brand of Liapour.[2]

LECA is a small, lightweight, and bloated particle of burnt clay. The base material is plastic in combination with clay, extensively pre-treated, then heated and expanded in a rotary kiln. Finally, the product is burned at 1100 °C to form the finished LECA product. [3]

Another growing media now entering the market is Klayton (Fig. 2). It was designed and manufactured by AquaOrganika, a division of Poseidon Sciences Group focusing on aquaponics research. AquaOrganika, whose operation is based in the Philippines, aims to develop the tropical aquaponics technology through intensive research and product development. Klayton, the first innovation of AquaOrganika, is composed of natural clay from the mountains of Panay Island in Western Visayas, Philippines. Just like Hydroton and LECA, Klaytons are small clay balls, with sizes ranging from 5mm to 20mm in diameter. It is manually shaped into balls, air-dried and baked. Klaytons are also pH inert, odourless, and tough. It is also free from toxic materials and heavy metals because the clay is taken from the uplands far from any point source of industrial pollution.

Figure 1. Light Expanded Clay Aggregate (LECA)

Figure 2. Klayton

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A successful aquaponics industry requires identification of the best growing media that could facilitate efficient filtration and nitrification of fish waste water. There is a dearth of information in the scientific literature about the efficiency of different types of growing media. This study was initiated as part of the program to objectively assess the performance of commercially available materials. The first phase of the evaluation was to examine the physical profiles of two media—Klayton and LECA.

Materials & Methods

Apparent volume, open pore volume, specific surface area and water absorption capacity were measured using methods described in ICCROM-UNESCO-WHC ARC Laboratory Handbook [4].

Chinese-made LECA were purchased from Hydroponic Garden Supply (Manila, Philippines) and Klayton was supplied by AquaOrganika (Miagao, Iloilo, Philippines). Mitutoyo Vernier Caliper and AWS Digital Balance were used to measure the weight and length of media, respectively. Close-up photographs were captured by Sony Cybershot Digital Camera DSC-T70 and Dino-Lite Digital Microscope. The experiment was conducted at the Poseidon Sciences Group Laboratory in Miagao, Iloilo, Philippines.

The samples were washed with deionized water to eliminate the powdered material from the surface and dried in the oven for 24 hours at 60 ⁰C and then placed in the desiccator with silica gel to cool off. Dry weight of the samples was recorded as (mc). The samples were totally immersed in the glass container with deionized water. The samples were taken out of the container after 8 hours and the weight recorded as (ms). The samples were re-immersed again until the difference in weight between 2 successive measurements is less than 1% of the amount of water absorbed. The saturated samples were placed in the graduated cylinder and filled with deionized water to measure the increase in volume indicated on the cylinder as the apparent volume Va (mm3).

Open pore volume (Vop) corresponds to the volume of water absorbed by the sample [4].

Vop = ms - mc

Apparent volume (Va) is the volume of a solid including the space occupied by the pores [4]. Effective porosity (%P) is the percentage of interconnected pore space which is defined as the ratio between the volume of the open pores (Vop) and the apparent volume (Va ) [4].

%P = 100 x (Vop /Va )

Real volume (Vr) is the difference between apparent volume (Va) and open pore volume (Vop) [4].

Water absorbance (% Wa) is the quantity of water absorbed by the sample immersed in deionized water at successive time intervals and expressed as a percentage of the dry mass of the sample [4].

%Wa = 100 x (mc – ms)/ms

All measurements were made at ambient room temperature ranging from 23 oC to 27 oC. A two-tailed independent Student’s T-test was used to determine the significance data between Klayton and LECA.

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Results and Discussion Table 1. The physical profile of Klayton and LECA. A total of 20 samples of each media were measured for diameter and surface area. Measurements of weight, open porosity, water absorption and water absorbance were based on triplicate samples. The data are expressed as mean + standard deviation.

Parameters Klayton LECA P value Diameter, mm 14 ± 0.9 6.4 ± 0.8 0.000002 Weight, g 2.6 ± 0.1 1.4 ± 0.1 0.003 Surface Area, mm2 741 ± 148 127 ± 34 0.0005 Open Porosity, % 27 ± 3 8 ± 3 0.003 Water absorbance, % 18 ± 2 14 ± 7 0.60 Water absorbed /surface area, µl/ mm2 0.63 ± 0.1 0.16 ± 0.1 0.002 Water absorbed /volume of media, ml/mm3 275 ± 28 86 ± 30 0.003

Table 1 summarizes the physical characteristics of Klayton and LECA measured in this study.

The weight of the growing bed is a major consideration when designing an aquaponics system. The heavier the media the more durable the material and the more sturdy the support structure needed for the design. A single LECA was half the weight and half the diameter of a single ball of Klayton. This difference is more visible when photographed side by side (Fig. 3). Clogging is a major problem when the grain size was small and water flow was large [5]. The bigger the size of the media, the more air space between clay pellets for the roots to breathe and grow.

Porosity is fundamental in understanding the phenomena of water transport through the pore structure and interaction between the media and water. Water can penetrate a solid because there are interconnected channels (micro and macro pores) inside the solid that facilitate its transportation [4].

Figure 4 shows the cross section of LECA when cut in half. Close examination of the exposed surface shows that there are numerous internal cavities present which do not connect to the outer surface. These small, air-filled cavities give LECA its strength and thermal insulation properties which are beneficial in the construction of buildings but may not be optimal for growing plants in an aquaponics system [3]. In contrast, Klayton samples did not show any visible internal cavities.

Figure 3. Side by side photograph of LECA and Klayton

Figure 4. Comparison of cross-sections of Klayton and LECA by Dino-Lite Digital Microscope at 50x magnification

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Both media show irregular surface architecture and roughness, which are conducive to attachment of biofilm to enable more efficient biofiltration (Fig. 4). The single hole (internal diameter of 3 mm) through the Klayton ball serves two functions: a) increase surface area; and (b) allow the root system to go through the hole to enable better hold on the Klayton ball. The calculation of the total surface area of Klayton shown in Fig. 6 and Table I took into account the internal surface area of the central cylindrical hole through the Klayton.

The open porosity test shown in Table I and graphically shown in Fig.7 confirmed the significant difference between Klayton (27% porosity) and LECA (8% porosity). Because of the internal air-filled cavities, LECA samples were observed to float in water while the Klayton sunk immediately to the bottom (Fig. 8). Even after 7 days of immersion, only 10% of the immersed LECA had sunk to the bottom. The video of both media under water immersion show air bubbles emanating only from the surface of Klayton suggesting that there are micropores in the Klayton not visible by photography. Such micropores provide additional surface area to the Klayton, but not quantifiable using current measurement techniques available to the authors.

An important factor in determining the efficiency of biofiltration is the size of the area penetrable by water [5]. The presence of a larger surface area in Klayton will likely create improved biofiltration through greater bacterial biofilms.

Water absorption test by total immersion measures the water absorbance and the maximum water absorption capacity. The total 0 200 400 600 800 1000

Klayton

LECA

mm2

Surface Area

Figure 6. Comparison of surface area of Klaytons and LECA. Expressed in mm2 ± SD

Figure 5. Comparison of surface area of Klayton and LECA by Dino-Lite Digital Microscope at 100x magnification

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quantity of water absorbed is related to the total open porosity [4].

LECA was primarily designed for construction of building as a light weight additive to improve strength and thermal resistance. Since there are many different manufacturers of LECA around the world, each product is likely different because of varying manufacturing processes. A manufacturer in United Arab Emirates stated that the water absorbance of LECA is 18% by weight for the size of 0-25 mm in diameter and it is designed to inhibit water absorption [3]. Water absorption test showed that the water absorbance of LECA was 14% and Klayton was 18% (Fig. 11) which was not statistically significant.

Water absorbance per volume of the media was also evaluated. Media volume became important when considering the surface area and bio filter space [6]. Hence, comparison of the water absorbance of different growing media at the same volume was needed. Klayton showed a significantly higher water absorbance/surface area and water absorbance/volume of the media as compared to LECA (Fig. 9, 10).

LECA Klayton

Figure 8. Comparison of LECA and Klayton in water absorption test

0 100 200 300 400

Klayton

LECA

ml of Water/mm3

Water absorbed/Volume

Figure 9. Comparison of water absorbed/volume of Klaytons and LECA. Expressed in ml/mm3 ± SD

Figure 10. Comparison of water absorbed/surface area of Klaytons and LECA. Expressed in µl/mm3 ± SD

0.00 0.20 0.40 0.60 0.80

Klayton

LECA

µl of water/mm2

Water absorbed/Surface area

Figure 7. Comparison of open porosity of Klaytons and LECA. Expressed in % ± SD

0 10 20 30 40

Klayton

LECA

% Open Porosity

Figure 11. Comparison of water absorbance of Klaytons and LECA. Expressed in % ± SD

0 5 10 15 20 25

Klayton

LECA

Water Absorbance (%)

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Conclusions and Recommendations

Klayton is likely better as a growing media for aquaponics system because of the higher surface area, higher water absorption/surface area, higher water absorption/volume and higher open porosity compared to LECA. Klaytons have more surface area for the growth of nitrifying bacteria, leading more efficient as a bio filter in an aquaponics system.

This study is part of an ongoing series of studies to quantify the performance of different media that are currently being used in aquaponics. It may be possible that the LECA used in the current study may not represent all of the different LECA since manufacturing methods and chemicals used may vary from company to company. We intend to explore this possibility in the future.

Klayton is made from natural clays in the absence of chemical additives. LECAs are made in an industrial process requiring chemicals to create the internal cavities as well as other chemical processes to impart thermal resistance. The chemical composition of LECA may render it unsuitable for organic farming. More research needs to be undertaken regarding the chemical composition of LECA and potential adverse effects of chemical residues. Chemical profiling must also be conducted to determine any heavy metals and toxic substances in the growing media which may affect the aquaponics system

Finally, nitrification test must be performed to confirm the bio filtration efficiency of Klayton over LECA.

Acknowledgement The authors wish to thank Araceli Adrias, Cheryl Arcete, Marlo Laguna, Kian Angelo Lorella, and Jaifreed Cabangal for their expert assistance.

References

1. Ebeling, J. Biofiltration-Nitrification Design Overview. Retrieved February 23, 2014, from http://ag.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop%20PP%20%20&%20Misc%20Papers%20Adobe%202006/7%20Biofiltration/Nitrification-Biofiltration/Biofiltration-Nitrification%20Design%20Overview.pdf

2. Lekang OI and Kleppe H. 2000. Efficiency of nitrification in trickling filters using different filter media. Aquac Eng 21, 181-199.

3. LECA. What is LECA. Retrieved February 21, 2014, from http://www.leca.ae/?q=WhatisLeca

4. ICCROM, UNESCO, WHC. 1999. ARC Laboratory Handbook. Retrieved February 5, 2014, from http://www.iccrom.org/pdf/iccrom_14_arclabhandbook01_en.pdf

http://ag.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop%20PP%20%20&%20Misc%20Papers%20Adobe%202006/7%20Biofiltration/Nitrification-Biofiltration/Biofiltration-Nitrification%20Design%20Overview.pdfhttp://ag.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop%20PP%20%20&%20Misc%20Papers%20Adobe%202006/7%20Biofiltration/Nitrification-Biofiltration/Biofiltration-Nitrification%20Design%20Overview.pdfhttp://ag.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop%20PP%20%20&%20Misc%20Papers%20Adobe%202006/7%20Biofiltration/Nitrification-Biofiltration/Biofiltration-Nitrification%20Design%20Overview.pdfhttp://www.iccrom.org/pdf/iccrom_14_arclabhandbook01_en.pdf

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5. Dicky H., Sung-Yong O. and Jae-Yoon J., Comparison of the Nitrification Efficiencies of Three Biofilter Media in a Freshwater System. Fish Aquat Sci 14(4), 363-369, 2011

6. Wheaton FW, Hochheimer JN, Kaiser GE, Malone RF, Krones MJ, Libey GS and Easter CC. 1994b. Nitrification filter design methods. In: Aquaculture Water Reuse Systems: Engineering Design and Management. Development in Aquaculture and Fisheries Science. Vol. 27. Timmons MB and Losordo TM, eds. Elsevier, Amsterdam, NL, pp. 127-171.

AbstractIntroductionMaterials & MethodsResults and DiscussionConclusions and RecommendationsReferences