A new water treatment system based on material circulation was constructed for purification of naturally polluted pond water in an aquarium. The water treatment system consisted of microbial columns with different flow rates (1.8 L/min/column in 6-columns unit and 2.9 L/min/column in 3-columns unit). Two hundred liters of water from a naturally polluted pond were treated for 14 days using the water treatment system. After treatment, the COD, TC, and TN had been reduced by up to 19.2%, 14.4%, and 20.1%, respectively. The bacterial biomass in the 3-columns unit was 7-fold higher than that in the 6-columns unit, and PCR-DGGE analysis showed slightly different bacterial communities between the two columns (<86%). The new water treatment system also worked efficiently in a fish-cultivated aquatic environment, with TC and TN removal rates of 190 mg/week and 260 mg/week, respectively.
Oceans and rivers have a self-purification process that occurs through water circulation to maintain the organic matter load at a low level [
However, limited water flow in lakes and ponds often causes inefficient self-purification [
This paper describes the development and construction of a new water treatment system based on material circulation by environmental microorganisms to purify water in a static water environment.
The water sample used in this study was taken from a small pond (Kitanoshin Pond) located in Kusatsu, Shiga, Japan (34˚98'N, 135˚96'E). A 200 liter water sample was taken from the pond every 14 days from 16 April 2014 to 16 February 2015.
Before construction of the new water treatment system, the efficiencies of various treatments were evaluated in a preliminary experiment (20 L water tank). The treatments used were: water circulation with faster water flow rate columns (3-columns unit) and slower water flow rate columns (6-columns unit), circulation with 3-columns unit only, circulation with 6-columns unit only, circulation only, and control (without any treatment). The columns were filled with polyvinylalcohol (PVA) sponge and the COD removal rate was used to evaluate the efficiency of each treatment. The preliminary experiment showed that a combination of water circulation with 3-columns unit and 6-columns unit was most efficient (COD removal rate > 70%). A new water treatment system was then constructed using a combination of water circulation with 3-columns unit and 6- columns unit in a 200 L water tank.
The efficiency of the new water treatment system was evaluated by measuring COD, TC, and TN in a 200 L experimental tank. The measurement was performed from April 2014 to February 2015 throughout the spring (March to May), summer (June to August), autumn (September to November), and winter (December to February). The water was treated in the experimental tank for 14 days, after which it was exchanged with fresh water.
Water quality parameters (COD, TC, and TN) were analyzed during treatment. The COD was analyzed using the permanganate based titrimetric method [
where 1 is the KMnO4 factor in 5 mol/L and 0.2 is the amount of oxygen in 5 mol/L KMnO4.
The COD removal rates were obtained through the formula:
where COD0 is the value of COD before treatment and COD14 is the value of COD after treatment.
The TC and TN were measured using a total organic carbon analyzer (TOC- VCPH, Shimadzu, Kyoto, Japan) and solid sample combustion unit (SSM-5000 A, Shimadzu, Kyoto, Japan) according to the manufacturer’s instructions. Total phosphorus (TP) and total potassium (TK) in the water was analyzed by using molybdenum blue method [
The number of total bacteria in the microbial columns was measured from a sample collected from the PVA sponge filled in the 3-columns unit and 6-col- umns unit. Briefly, the slow-stirring method was used to extract the environmental DNA (eDNA) of bacteria [
The 16S rRNA bacterial gene was amplified using primers DGGE-F (5’-CGCCC GCCGC GCCCC GCGCC CGTCC CGCCG CCCCC GCCCG CCTAC GGGAG GCAGC AG-3’) and DGGE-R (5’-CCGTC AATTC CTTTG AGTTT-3’) [
DGGE was performed using a D Code System (BioRad Laboratories Inc., California, USA). A total of 20 μl of PCR product were loaded into 40% (w/v) polyacrylamide gel with a denaturant gradient of 27.5% - 67.5%. The gel was then run in 1 × tris-acetate EDTA buffer at a constant voltage of 70 V at 60˚C for 15 hours. Next, the gel was stained using SYBR Gold for 20 min, then rinsed with distilled water. Cluster analysis of the DGGE band pattern was subsequently conducted using the FPquest Bioinformatics Software (BioRad Laboratories Inc., California, USA).
The new water treatment system was evaluated in water containing high levels of organic materials in a fish tank. A tank containing 200 L of tap water, 20 kg of sand sediment, and 12 goldfish maintained at room temperature (25˚C) was used in the experiment. The experiment was divided into two stages: before operation of the microbial columns (stage I) and after the operation of the microbial columns (stage II). Stage I was conducted for 21 weeks, and stage II for 18 weeks. Fish were fed 0.5 g fish feed (TC: 300,000 mg/kg and TN: 45,000 mg/kg) every day. Thus, the total carbon input during the experiment was 40,950 mg (22,050 mg in stage I and 18,900 mg in stage II), and the nitrogen input was 6140 mg, with 3310 mg in stage I and 2830 in stage II. The amounts of TC and TN (in 200 L of water and 20 kg of sediment) at the beginning and at the end of stage I and stage II were measured to analyze their mass balance (input and accumulation). The differences in TC and TN accumulation in CO2/N2 and goldfish between stage I and stage II were used to analyze the removal efficiency of TC and TN. Finally, the removal rate of TC and TN in the environment during treatment was analyzed based on the removal efficiency value.
A new water treatment system was constructed using water circulation and activated aerobic and anaerobic microorganisms. The schematic diagram of the new water treatment system is shown in
Water used in this study was taken from Kitanoshin Pond, Shiga, Japan (34˚98'N,
135˚96'E). The COD, TC, and TN values in all seasons are shown in
The water was treated using the new water treatment system to evaluate the efficiency of this system to reduce COD, TC, and TN in the water. The COD, TC, and TN removal rates were reduced in all seasons (
Season | Date | COD | TC | TN | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Day 0 (mg/L) | Day 14 (mg/L) | Removal rate (%) | Average removal rate (%) | Day 0 (mg/L) | Day 14 (mg/L) | Removal rate (%) | Average removal rate (%) | Day 0 (mg/L) | Day 14 (mg/L) | Removal rate (%) | Average removal rate (%) | ||
Spring | April 16 | 3.4 | 3.4 | 0.0 | 7.5 | 3.5 | 3.5 | 0.0 | 0.7 | 0.1 | 0.1 | 0.0 | 18.0 |
May 1 | 3.2 | 3.2 | 0.0 | 3.5 | 3.5 | 0.0 | 0.3 | 0.2 | 34.4 | ||||
May 16 | 4.0 | 3.1 | 22.5 | 4.9 | 4.8 | 2.0 | 0.4 | 0.3 | 37.5 | ||||
Summer | June 1 | 3.8 | 3.2 | 15.8 | 24.6 | 5.9 | 4.3 | 27.1 | 20.5 | 0.3 | 0.3 | 0.0 | 28.0 |
June 16 | 5.0 | 3.0 | 40.0 | 5.7 | 4.1 | 28.1 | 0.8 | 0.1 | 81.8 | ||||
July 1 | 8.1 | 7.1 | 12.4 | 5.6 | 5.2 | 7.1 | 0.4 | 0.4 | 0.0 | ||||
July 16 | 8.0 | 5.8 | 27.5 | 6.2 | 5.7 | 8.1 | 0.6 | 0.3 | 49.2 | ||||
August 1 | 6.1 | 5.2 | 14.8 | 5.4 | 4.7 | 13.0 | 0.6 | 0.6 | 0.0 | ||||
August 16 | 8.1 | 5.1 | 37.0 | 6.8 | 4.1 | 39.7 | 0.5 | 0.3 | 37.0 | ||||
Autumn | September 1 | 6.6 | 5.1 | 22.7 | 23.0 | 5.0 | 4.7 | 6.0 | 18.6 | 0.3 | 0.3 | 0.0 | 12.8 |
September 16 | 13.4 | 10.4 | 22.4 | 7.1 | 5.6 | 21.1 | 0.7 | 0.6 | 6.2 | ||||
October 1 | 8.5 | 6.0 | 29.4 | 5.5 | 4.5 | 18.2 | 0.8 | 0.4 | 54.4 | ||||
October 16 | 6.5 | 4.8 | 26.2 | 5.2 | 3.6 | 30.8 | 0.3 | 0.3 | 16.1 | ||||
November 1 | 6.7 | 4.9 | 26.9 | 4.7 | 3.4 | 27.7 | 0.3 | 0.3 | 0.0 | ||||
November 16 | 4.3 | 4.3 | 0.0 | 3.8 | 3.5 | 7.9 | 0.5 | 0.5 | 0.0 | ||||
Winter | December 1 | 2.8 | 1.9 | 33.2 | 21.7 | 3.3 | 1.9 | 42.4 | 17.8 | 0.4 | 0.2 | 47.5 | 21.5 |
December 16 | 2.0 | 2.0 | 0.0 | 2.1 | 2.1 | 0.0 | 0.3 | 0.3 | 0.0 | ||||
January 16 | 3.7 | 2.0 | 46.0 | 2.8 | 2.2 | 21.4 | 0.3 | 0.2 | 40.7 | ||||
February 1 | 3.3 | 3.3 | 0.0 | 2.6 | 2.3 | 11.5 | 0.3 | 0.2 | 19.2 | ||||
February 16 | 4.4 | 3.1 | 29.6 | 2.9 | 2.5 | 13.8 | 0.3 | 0.3 | 0.0 | ||||
Average | 19.2 | 14.4 | 20.1 |
The total bacteria in both 3-columns unit and 6-columns unit were analyzed for environmental DNA (
in water flow rate in the columns led to supply of different aerobic conditions. The faster water flow rate in the 3-columns unit appears to supply oxygen to enhance the total bacterial number. Different bacterial diversities were also shown in 3-columns unit and 6-columns unit owing to differences in oxygen level.
The new water treatment system was used for evaluation of water treatment in a fish-cultivated aquatic environment. Before starting the operation (stage I), 22,050 mg of carbon and 3310 mg of nitrogen were added into the environment by fish feed (
Parameter | Stage I | Stage II | ||||||
---|---|---|---|---|---|---|---|---|
Input (mg) | Water | Sediment | CO2/N2 and accumulation in fish | Input (mg) | Water | Sediment | CO2/N2 and accumulation in fish | |
TC | 22,050 | 1850 | 4000 | 16,200 | 18,900 | −700 | 0 | 19,600 |
TN | 3310 | 1270 | 1800 | 240 | 2830 | −880 | −1200 | 4910 |
The new water treatment system was operated to purify the water after 21 weeks (stage II). During stage II, there was no accumulation of carbon and nitrogen in either the water or sediment (
The accumulation of TC and TN during the experiment (stages I and II) was analyzed (
A new water treatment system based on material circulation was constructed for purification of water in a natural static environment. The system was designed based on a water flow environmental self-purification mechanism [
Enhanced aerobic and anaerobic bacteria accelerated the carbon and nitrogen removal in the water through several processes [
Parameter | CO2/N2 and accumulation in fish | Total removal value by the system (mg) | Removal value in a week by the system (mg) | |
---|---|---|---|---|
Stage I | Stage II | |||
TC | 16,200 | 19,600 | 3400 | 190 |
TN | 240 | 4910 | 4670 | 260 |
rials in the aquatic environment. The new water treatment system also worked efficiently in a fish-cultivated aquatic environment, and the nitrogen removal rate became higher. The high nitrogen concentration in the aquatic environment may stimulate activation of denitrifying bacteria in the 6-columns unit [
Use of activated sludge system is one of the extensively used methods for treating polluted water. Activated sludge system carries both aerobic and anaerobic tanks, but it requires huge energy [
Perwira, I.Y., Hanashiro, T., Salamah, L.N., Adhikari, D., Araki, K.S. and Kubo, M. (2017) Construction of a New Water Treatment System Based on Material Circulation. Journal of Water Re- source and Protection, 9, 1014-1025. https://doi.org/10.4236/jwarp.2017.98067