Integrated Water Clarification

Abstract

An integrated water clarification method for industrial and communal wastewater treatment and recycling is presented here. The clarification is hermetic and consists of four seamless phases: (1) separation of dissolved ingredients, (2) molecular activation, (3) clarification reactions and (4) replacement dissolution. It separates dissolved gases such as radon, carbon dioxide, hydrogen sulfide and hydrocarbons and dissolved solids such as iron, manganese, calcium, fluorine and phosphorus. The molecules are activated, and clarification reactions occur immediately by the suction of clean air, oxygen or ozone. The clarified water is aerated or oxygenated immediately after clarification. All this happens within a second or a few seconds depending on the water volume to be clarified. The integrated clarification is based on the fact that water itself is pure; it just picks up and easily transfers heavy loads. In the natural water cycle, the water eliminates its load by vaporizing. The integrated clarification separates the load in such a way that most of it can be removed and recycled. Treated water can be recycled and discharged into nature with respect to its natural value. The treated water can influence the natural water cycle by being sprayed on the ground and plants for solar vaporization and cooling of the climate. The load of the ocean can be reduced significantly. Integrated water clarification is performed under flowing conditions in a tube by kinetic energy. Gases and possible additives are sucked by a vacuum caused by a symmetrical nozzle design of two curved flow channels. It reduces water, energy and chemical consumption, and the capital and operational costs are low.

1. Introduction

The present wastewater treatment needs a new perspective and environmental respect. In the present water cycle, seas and oceans are rubbish dumps. The loads of rain and wastewater are pumped as quickly as possible into the rubbish dumps through the large underground sewer network. Climate cooling by water evaporation is reduced to a negligible level. There is little water and ingredient recycling. Despite the increase in power consumption and technology intensity in wastewater treatment, the environmental conditions indicate unsatisfactory results. Furthermore, the sewer network causes serious floods. Many serious problems, disasters and serious microbial growth can be avoided by water clarification and wide-area water buffers with solar evaporation.

The integrated water clarification process, design criteria, related devices and some practical case studies are presented here. This clarification consists of four seamless treatment phases, and as the fifth step, a firm gas bubble is generated as follows:

1. Separation of dissolved ingredients

2. Activation of molecules

3. Clarification reactions

4. Replacement dissolving

5. Bubble generation in water flow

There are still the following guiding principles for development and related research:

• Water itself is a pure substance that easily picks up heavy loads and can be purified by releasing the load.

• Water is present everywhere, and it performs the largest transportation system in the world.

• The clarification is to be well controlled and hermetic.

• Water purification can be combined with other water processes, such as hydro power and fountains.

• Treated wastewater is discharged into the natural water cycle via climate and natural wellness

• Water recycling is maximized in use with the lowest energy consumption and heat generation.

• Treated wastewater can be reused for climate cooling, such as solar evaporation.

• The solution is to be economically competitive, and its life cycle costs are a concern.

• Humans have made many mistakes and malfunctions in the natural water cycle that should be identified and corrected.

• Natural energy, e.g., potential and direct solar energy, is utilized.

Figure 1 summarizes the development principles. Integrated clarification fulfills these development and design principles in several areas, but further development and research are needed for many challenging applications. The separation of dissolved ingredients is effective, but removing these components is challenging for certain substances, such as chlorine and salt.

Figure 1.

Water recycling is integrated into the natural water cycle. There are several recycling and evaporation systems. Water picks up heavy loads that are to be released where it is caused, and there are only two acceptable options—Recycling or evaporation—For the water cycle.

The development is performed by small innovative companies, Hilla Consulting Oy, T₂O Consulting Oy and T₂O Consulting GmbH. Application development and sales have been completed together with SansOx Ltd. Several universities have contributed to related research activities. T2O Consulting GmbH has manufactured functional and visible prototypes and tested them according to several thousand integrated clarification criteria.

2. Integrated water clarification

A new hermetic water treatment process and device called OxTube Integrated Clarification and some of its applications are briefly presented here. The focus is on wastewater clarification and recycling. However, integrated clarification is suitable for the treatment of all kinds of water matrices. The OxTube is the basic water treatment machine and module that can be modified easily for various tasks, water matrices and installations, and it fulfills the guiding development principles set in Chapter 1, which is the most important.

To clarify water all the way, the following main criteria are identified:

• Dissolved ingredients should be separated, and molecules should be activated first in the clarification process.

• Other molecules present should also be activated or filtered out before integrated clarification, depending on the case.

• The wastewater content of various solids and chemicals distributed unevenly should be considered in the early phase of the integrated clarification process.

• Clarification gases should be fed and mixed evenly to ensure a high probability of collisions between molecules.

• The clarification should be well controlled, and all kinds of disturbances should be eliminated in the clarification process.

• It is desirable to refresh the water after clarification reactions by oxygenation or aeration.

• The removal of gases and particles should be considered after clarification.

• A dirt-free system should be considered.

The following solutions for several alternatives were developed after analysis and test runs:

• The nozzle was identified as the key element. Hundreds of nozzle models were produced and tested.

• A nozzle with curved water channels was identified as the best solution for separation, molecular activation, gas suction and mixing.

• The curved channels generate a pressure difference in the water flow divided into two channels, and a vacuum pocket is created in the middle of the nozzle zone.

• The pressure difference and vacuum pocket separate and activate ingredients dissolved in the intake water.

• The nozzle structures of two or more curved channels must be accurately symmetrical.

• Figure 2 shows the visible efficiency of the separation and activation as well as the clarification with Swiss Alpen household water.

Figure 2.

Efficiency of OxTube integrated clarification with air; Swiss Alpen tap water was used only for soluble ingredient separation and molecular activation, and the integrated clarification was performed under the same conditions. Separation, activation, clarification and replacement are performed seamlessly within 1 second or less in an OxTube [1].

The channels are designed in such a way that there is no discontinuity that might cause disturbances in the clarification and dirt sticking in the nozzle.

The vacuum pocket sucks gases and possible chemicals and mixes them effectively and evenly in the water flow. Figures 3 and 4 illustrate the effective suction and even mixing. The mixture of water and air is evenly foggy, as shown in Figures 2 and 3. The spray of the mixture of water and air is firm and coherent, as shown in Figure 4. The air suction is great; it can be more than 10 times greater in volume than the water flow, and the gravity decreases. No additional energy is needed.

Figure 3.

The OxTube integrated water clarification was visualized with air suction. Integrated clarification is performed within less than a second [1].

Figure 4.

The performance of the OxTube machine in gas suction and mixing, as well as in clarification and replacement dissolving, is great and efficient. No additional energy is needed in the integrated clarification. The height of the mixture is nine times greater than that of plain water under the exact same conditions of water intake.

3. OxTube machine

To optimize the total solution according to the challenging customer needs and concerns of various water matrices, a modular structure of the system is applied. Various customized solutions with natural respect are built from the same modules. The OxTube Machine is the key module in integrated clarification and has low power consumption. The treatment does not require any additional energy, but side processes such as ozone and chemical generation and feed might require power. Some solutions installed in pressurized piping might require compressed air. However, it is possible to avoid this by the system design.

The OxTube Machine seamlessly performs the following clarification phases:

• Separation of the dissolved ingredients (Figure 2)

• Activation of molecules (bubbling of reaction gases in Figure 2)

• Clarification gases and possible chemicals (Figures 3 and 4)

• Performance of the clarification reactions (Figure 2 right)

• Replacement dissolving

• Generation of gas bubbles (Figure 4)

The separation of the dissolved components and molecular activation are shown in Figure 2 (left) when the water was removed through an OxTube without air suction. Separated gases cause smells and solid white particles. Molecular activation generates light bubbling and a gaseous smell. Immediate clarification can be achieved by air feeding into the activated water. Integrated clarification with air suction is completed within less than a second, as shown in the right panel of Figure 2.

The upper photo of Figure 3 visually shows the even mixture of water, separated ingredients and air in the tube. The mixture is seen in white. Its gravity is much lower than that of the intake water matrix. The gravity reduction in the nozzle zone could be 1/10 that of water. The probability of collisions among molecules, particles and bubbles is extremely high. The lower photo of Figure 3 shows the water flow when the air channel is closed. No turbulence or cavitation can be observed.

Bubble generation and mixing with water are visualized in Figure 4. The height of the outtake spray increases nine times when the air channel is open. The mixture gradually turns light in the nozzle. The spray of the mixture stays coherent all the way up, which is an essential feature of the OxTube Machine.

Figure 5 shows the oxygenation efficiency of the OxTube at an early stage development [2]. Since 2016, the separation of dissolved ingredients has improved, and gas suction has increased by a factor of 5. Losses are measured today in terms of mass flow due to large gravity drops and changes from incompressible to compressible liquids in the nozzle zone. The mass flow losses are measured to be less than 2%.

Figure 5.

Oxygenation efficiency of the OxTube in the early stage of development [2].

The OxTube Machine is presented in Figure 6. It consists of a DuOx nozzle, an air suction nipple, an outer tube and flanges. For small flanges, the flanges are replaced by standard thread fittings. All the fittings are metal-to-metal tight fits; there are no individual seals at all. Welding is minimized; only the flanges must be welded to the outer tube. The structure is very compact and easy to maintain in good condition.

Figure 6.

The OxTube machine with gas and chemical suction is compact and includes standard fittings. It can be installed in various water treatment systems. The pressure norm is up to PN40.

OxTube machines are easy to modify and optimize for various water matrices and treatments. Figure 7 shows the machine modified to realize heavy gas removal and water clarification. There is a booster nipple for pressured air feed that removes separated heavy gases such as radon and carbon oxide.

Figure 7.

OxTube machine with suction and booster nipple. The module is the same as that in Figure 6 and is composed of a booster nipple.

The two serial OxTube machines were combined so that the first step involved separation and activation, and the second step involved clarification, dissolution and bubble generation (Figure 8). Clarification performance is improved, particularly in very challenging cases. Furthermore, a booster can be applied in the second machine when heavy gases are involved in the integrated clarification.

Figure 8.

With the combination of two OxTube machines, the first is responsible for separating the dissolved ingredients and molecular activation, and the second involves bubble generation, clarification and replacement dissolution. This is a solution for dirty waters such as wastewaters.

There are many other ways to determine various combinations of the same modules to create the best solution to meet environmental and economic requirements. Clarification, disinfection and oxygenation of a water matrix can be combined in one OxTube by ozone or a mixture of ozone and air feed. Growing environmental problems, microbial variation and growth and drug residues are eliminated at the same time as water clarification.

Details of DuOx Nozzle are not presented here due to its dedicated structure that is to be kept in secrecy. It is the active element of the integrated clarification. Its functional features are presented above in this chapter.

An OxTube Machine separates dissolved ingredients, but removing them from the mixture requires further attention. An OxTube Machine generates a large amount of overdosed bubbles by gas suction, which can be used for flotation (Figure 9). The collision probability of particles and bubbles is high, and attachment is identified to be good, so flotation is a natural method of particle removal; it is similar to a built-in feature. Particle attachment occurs in the OxTube and Fitting Modules before the flotation cell, and the efficiency is improved. Compressed air and diffusers can be eliminated when an OxTube Machine is applied. Of course, all the filtering methods can be applied for particle removal after integrated clarification.

Figure 9.

The OxTube machine generates bubbles and even mixtures under hermetic tube conditions. The probability of particles and bubbles being met is high, and particle attachment already occurs in the OxTube and subsequent tubes before the flotation cell [1, 3, 4].

Figure 10 shows the efficiency of the integrated clarification according to one hundred real test runs completed with industrial wastewater. Turbidity of the clarified.

Figure 10.

OxTube tests of industrial wastewater resulted in a turbidity of 0.0 NTU. The clarified water is recyclable in industrial process use.

The amount of wastewater returned to 0.0 NTU within 30 minutes. Only an OxTube Machine, a pump and an open outtake vessel were used, and no filters were used. The treated water was identified as recyclable for industrial purposes. Recycling for household purposes needs further investigation and verification. The potential to address all of these water quality issues exists. Discontamination can easily occur with ozone, and the pH can be controlled with CO₂. Chemical residues can be removed by integrated clarification, as verified previously, or by additional filtering.

4. Water treatment unit

There are many methods and combinations for applying integrated water clarification technology and removing separated water loads. The basic water treatment unit called the WTU is presented in Figure 11. It consists of an OxTube Machine and a Gas Removal.

Figure 11.

Water treatment unit for most of the water integrated clarification cases. It consists of an OxTube machine, a gas removal GasRemox and a fitting module. A 60% microbe reduction was achieved with air suction, and a 100% reduction was achieved with ozone feed.

GasRemox and Fitting Module. It was developed for industrial process water, intake water from lakes and pretreated communal wastewater. All kinds of OxTube machines and modular combinations can be applied in the WTU. Only the most challenging water clarification cases are presented here.

Disinfections of various water matrices, including communal and hospital wastewater, can be disinfected by ozone instead of air. Table 1 presents the results for the disinfection of hospital wastewater. A microbe reduction of 100% was achieved together with clarification and oxygenation of the over 20_{mg O2}/L.

Table 1.

Disinfection efficiency of the integrated water clarification of the OxTube: 100% reduction of E. coli and MS2 was achieved with an O₃ feed of 2 l/min within 0.7 s, an increase in the oxygen concentration over the MR of 20 mgO₂/l, and no significant ozone residues/Savonia University of Applied Sciences in Kuopio [5].

The efficiency of the OxTube system for the removal of pharmaceutical and chemical residues from city wastewater is presented in Table 2, which includes comparisons with two present systems. Pharmaceutical residues are a fast-growing disaster in natural water and ground. Approximately 90% of these residues were split, clarified and removed only by one run through an OxTube Machine to an open vessel without any filters. Two runs result in a 99 percent reduction. The city wastewater was clarified and oxygenated at the same time as the drug residues were removed. The present wastewater purification systems separate only 1/4 of the OxTube performance. The removal of drugs by the present systems and filtering leads residues to ground or back to water, which is unacceptable. Many chemicals, such as DDT, aldrin, chlordane, chloroform, and hexachlorobenzene, have been used for decades and have led to the natural and food chain. The present treatment systems are not able to eliminate these chemicals, similar to drug residues.

Pharmaceutics and other substances	OxTube Ozone Treatment			Present Method 1		Present Method 2
	Initial μg/l	Residue μg/l	Reduction %	Resudue μg/l	Reduction %	Residue μg/l	Reduction %
Cetirizine	5,8	0,006	99,9	4	<20	4	<20
Benzotriazole	2,8	0,896	68	1	63	2	<20
Furosemide	1,8	0,054	97	1,4	<20	1,4	<20
Hydrochloricazide	1,8	0,162	91	1,4	<20	1,4	<20
Diclofenac	1,5	0,004	99,7	1,2	<20	1,2	<20
Lamotrigine	1,4	0,756	46	1,1	<20	1,1	<20
Losartan	1,2	0,005	99,6	1	<20	1	<20
Losartan	1,2	0,246	79,5	0,7	<20	0,7	<20
5-methylbenzotriazole	0,83	0,191	77	1,4	<20	1,4	<20
Diatrizoate	0,70	0,147	79	0,6	20	0,5	<20
Atenolol	0,56	0,118	79	0,42	<20	0,35	22
Carbamazepine	0,53	0,048	91	0,4	<20	0,4	<20
Clozapine	0,53	0,053	90	0,4	<20	0,4	<20
Bisoprolol	0,50	0,105	79	0,1	77	0,4	<20
Tramadol	0,43	0,043	90	0,3	<20	0,3	<20
Citalopram	0,42	0,013	97	0,2	<20	0,2	<20
Piperacillin	0,29	0,009	97	0,32	48	0,2	<20
4-acetamidoantipyrine	0,29	0,015	95	0,15	21	0,15	<20
Azithromycin	0,20	0,012	94	0,14	<20	0,14	<20
Mirtazapine	0,17	0,006	96,4	0,08	31	0,11	<20
Atorvastatin	0,14	0,013	91	0,09	55	0,09	66
Propanolol	0,11	0,010	91	0,09	<20	0,09	<20
Quetiapine	0,11	0,006	95	0,08	<20	0,08	<20
Naproxen	0,10	0,020	80	0,07	<20	0,07	<20
Desloratadine	0,081	0,022	73	0,1	25	0,09	33
4-formylaminoantipyrine	0,077	0,022	71	0,04	52	0,06	<20
Bezafibrate	0,069	0,014	79	0,01	78	0,05	<20
Fluvastatin	0,068	0,011	84	0,07	26	0,08	<20
Metronidazole	0,064	0,035	45	0,04	23	0,05	<20
Sotalol	0,064	0,010	84	0,06	<20	0,06	33
Sulfamethoxazole	0,063	0,011	83	0,05	<20	0,05	<20
Ketoprofen	0,059	0,042	28	0,03	62	0,02	80
Sertraline	0,05	0,011	79	0,03	<20	0,03	<20
Sulfadiazine	0,042	0,013	70	0,03	<20	0,03	<20
Clarithromycin	0,033	0,011	68	0.03	<20	0,03	24
Ramipril	0,031	0,008	74	0,02	<20	0,02	<20
Amiloride	0,023	0,014	38	0,01	<20	0,01	<20
Roxithromycin	0,008	0,003	62	0,01	<20	0,01	<20
Xylometazoline	0,013	0,002	86	0,006	<20	0,006	<20
Warfarin	0,007	0,020	<20	0,02	24	0,02	<20
Caffeine		0,018	<20	0,018	<20	0,011	52
Verapamil		0,010	<20	0,01	<20	0,01	24
Total Drug Emission Load Reduction	24,162	3202	86,75	17,194	28,83	18,317	24,18

Table 2.

Removal of pharmaceutics and some other substances from the purified city wastewater of Kuopio Finland with OxTube integrated clarification treatment within a second.

Complex molecular structures of the pharmaceutics are split in separation phase before activation and clarification [4].

The heavy gas removal facility is presented in Figure 12. It is applied for radon gas removal in the intake of ground water. The performance of Rn removal can be seen in Table 3. Two WTU facilities with a compressor were installed in the present ground water intake after the pump. The intake water was clarified and aerated at the same time as Rn removal.

Figure 12.

Water treatment unit for heavy gas removal, such as Rn and CO₂. It consists of an OxTube machine with a booster, a gas removal GasRemox and a fitting module. Compressed air is used for separation, heavy gas blow-up and water clarification.

Water flow	Date of Sample	Monitoring Data						Rn Removal Bq/l
		Pressure psi					Raw Water	Treated Water	Reduction Bq/l	Reduction %	Acceptance
		Pump out	OxTube 1	OxTube2	Distr. Line	Δ
62.5 m^3/b	1809–19	60	52	48	60	0	55	9	46	83.6	Passed
	1909–1919	60	52	48	60	0	50	8	42	84.0	Passed
	2309–19	60	52	48	60	0	53	4	49	92.5	Passed
	2409–19	60	52	48	60	0	52	5	47	90.4	Passed
	2509–19	60	52	48	60	0	51	4	47	92.2	Passed
	2609–19	60	52	48	60	0	47	5	42	89.4	Passed
	3009–19	60	52	48	60	0	43	8	35	81.4	Passed
	0110–19	60	52	48	60	0	52	7	45	86.5	Passed
	0210–19	60	52	48	60	0	45	6	39	86.7	Passed
	0310–19	60	52	48	60	0	47	6	41	87.2	Passed
	0710–19	60	52	48	60	0	57	8	49	86.0	Passed
	0810–19	60	52	48	60	0	56	6	50	89.3	Passed
	0910–19	60	52	48	60	0	50	5	45	90.0	Passed
	1410–19	60	52	48	60	0	42	6	36	85.7	Passed
	1510–19	60	52	48	60	0	52	6	46	88.5	Passed
	2810–19	60	52	48	60	0	50	7	43	86.0	Passed
Requirement							52	11		79.0

Table 3.

Radon gas removal by two WTUs with compressed air and boosters from a ground water intake.

The WTU concept is presented in Figure 9.

5. Combined water clarification, disinfection and particle removal by flotation

The OxTube Machine can be integrated into VoxFlot flotation, as shown in Figure 13. The OxTube Machine generates many bubbles and even mixtures of water and bubbles under hermetic tube conditions, as illustrated in Figure 9. The probability of particles and bubbles being met is high, and particle attachment already occurs in the OxTube and subsequent tubes before the flotation cell [1, 3, 4, 6]. Two head vortex flows of the water and bubble mixture are generated in the VoxFlot flotation cell, which improves the particle attachment and extends the bubble path to the surface. The Bubble Trap speeds the vortex flow and pushes out a foam with particles on to the water surface. The clarified water is removed behind the bubble trap where no bubbles or particles exist.

Figure 13.

VoxFlot combined clarification, disinfection and flotation; 1. Water intake, 2. OxTube water clarification, disinfection and bubble generation, 3. Gas intake, 4. Flotation cell, 5. Bubble trap, 6. Foam collector, 7. Foam outtake, 8. Clarified and disinfected water outtake. The gas fed is ozone or a mixture of air and ozone. VoxFlot is presented in Refs. [1, 3, 4].

Water clarification, disinfection, oxygenation and particle removal by flotation can be combined by feeding ozone or a mixture of ozone and air through an OxTube.

Compared to straight flow flotation with air diffusers, bubble flow through an OxTube Machine and two head vortex flow significantly decrease the unit size. Chemical feed, if necessary, is completed directly in an OxTube. Furthermore, there are no rotational components involved. These features mean reduced capital and operational costs [4].

6. Natural waters

Currently, natural waters are generally wastewater sumps. Rivers, channels, dikes and drainpipes function as drains of the natural water cycle. Ponds, lakes and seas function as sewage basins. The pollution load of waters has increased and become more hazardous, particularly in population centers where water and rain quickly drain and sewage basins during the water cycle. The energy consumption of wastewater treatment has increased significantly, but it is deficient. Evaporation is reduced tragically, which means a significant loss of climate cooling power, more floods and increased desert area. It is urgent to refresh water and food chains.

The OxTube Machine and its integrated water clarification presented in Chapter 3 can be easily utilized in many ways and positions of the water cycle. Two examples are presented in Figures 14 and 15, which provide an idea of how easy it could be. The Water Clarifier has all the functions of an OxTube Machine. The combined water clarifier and fountain perform integrated water clarification and landscaping by water spray. Both of these examples are easy to install and movable. Their energy consumption is found to be negligible.

Figure 14.

The water clarifier refreshed the water with clean air without chemicals. Energy consumption is low.

Figure 15.

Combined water clarification and fountains.

Furthermore, integrated water clarification can be applied in all kinds of water transport vehicles without any additional energy consumption. Kinetic energy of the.

Vehicles in motion can be used for treatment. The flow resistance can be kept the same or even reduced by proper design. A cruising cargo ship would clarify sea water of more than 200,000 cubic meters a day at a depth of 4 meters.

7. Conclusions

OxTube Integrated Water Clarification is found to meet the environmental and economic guiding principles and criteria listed in Chapter 1. It has been applied successfully in the removal of pharmaceuticals, radon gas, calcium, manganese and iron from various water matrices and in disinfection of hospital wastewater with ozone. More than 40 different pharmaceutical residues at concentrations greater than 24 μg/L were removed.

Moreover, 90% of the respondents used OxTube Integrated Clarification within a second in one through one run [5]. Radon removal from 57 to 8 Bq/L is achieved continuously in five ground water intake installations at water plants. Disinfection of hospital wastewater with ozone resulted in a 100% reduction in microbes and the simultaneous clarification and oxygenation of the wastewater. A 60% reduction in the amount of virus was achieved by air suction without any other gas or chemical feed. Two runs with air might result in an approximately 80% reduction. Microbe growth and variation are reduced with only clean air suction and eliminated with ozone feed.

OxTube Machine and Water Treatment Units can be installed in various positions in present treatment processes and facilities for various water matrices. They can be applied in pretreatment, removal of the water load, clarification and oxygenation and disinfection of various wastewater matrices. Furthermore, the discharge water should be clarified in terms of its environmental removal.

The four-phase clarification and bubble generation of the OxTube Machine can be applied in all the areas of water purification and recycling described in Figure 1. Volumes of 0.1 to 1200 m³/h with one tube can be clarified and returned to the natural water cycle. OxTube machines can be integrated in and combined with present-day water systems. The DuOx nozzle can be integrated into hydro turbines by combining power and water treatment. Combined fountain and water treatment by the DuOx nozzle reduces energy consumption by half or more, and nature loves it according to fountain tests. DuOx Nozzle improves fire extinguishing, saves water and reduces damage caused by the addition of inert gas such as nitrogen and carbon oxide or smoke from the fire (see Figure 4). Watering and fertilization can be combined by means of exact spot farming. Integrated clarification should be started in water intakes because the water already contains too much waste, drug residues, radon and microplastics. Seas and oceans—refuse dumps of the water cycle—can be refreshed by integrating OxTube machines in ship structures. A cruising ship can treat 200,000 cubic meters of sea water a day without additional fuel consumption. There are more problems with water treatment than with natural water treatment.