Photosynthetic bacterium granulation method taking PAC as carrier and application of photosynthetic bacterium granulation method

Abstract

The invention belongs to the technical field of wastewater treatment, recycling and energy regeneration, and particularly relates to a photosynthetic bacterium granulation method with PAC as a carrier and application. According to the present invention, the granulation material polyaluminum chloride (PAC) is adopted as the core carrier, the single pure photosynthetic bacterium particle agglomeration can be stably achieved in combination with the adjustment of the water conservancy condition in the reactor, and the agglomerated photosynthetic bacterium particle can produce hydrogen in the high-concentration wastewater so as to achieve the efficient treatment of the wastewater. Results of the embodiment of the invention show that the overall particle size of the photosynthetic bacteria agglomerated by the method is larger, the chemical oxygen demand (COD) in a water body is obviously reduced, and the hydrogen production efficiency is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, resource utilization and energy utilization, and particularly relates to a photosynthetic bacteria granulation method using PAC as a carrier and an application thereof. Background Art

[0002] Photosynthetic bacteria (PSB) wastewater treatment technology is a new type of sewage treatment and resource recovery technology that can effectively convert pollutants in sewage into high-value-added resource products in cells, and can also produce hydrogen using high-concentration wastewater. However, in PSB wastewater treatment systems, photosynthetic bacteria are mostly in a suspended state, especially in hydrogen production systems, and there has been no research on the use of a single species of bacteria to produce hydrogen using granulated photosynthetic bacteria. Since most types of photosynthetic bacteria have poor aggregation ability, during the process of producing hydrogen using high-concentration sewage, the bacteria are mostly in a suspended state and difficult to separate by natural sedimentation. During the continuous operation of the hydrogen production reactor, the suspended microorganisms cannot be effectively separated from the supernatant and will continue to be flushed out with the effluent from the reactor, thereby reducing the content of effective microorganisms in the reactor and the stability of the system, resulting in poor system resistance to shock loads, low sewage treatment and hydrogen production effects, and other problems. In photosynthetic bacteria hydrogen production technology, the research on immobilization technology and separation technology of photosynthetic bacteria is one of the urgent needs to achieve continuous and stable operation of photosynthetic bacteria hydrogen production.

[0003] Currently, immobilization technologies, including encapsulation, adsorption, and cross-linking, are being studied for utilizing photosynthetic bacteria for wastewater treatment and hydrogen production. However, these immobilization technologies still have numerous drawbacks. Certain encapsulation and cross-linking agents used for encapsulation or cross-linking of photosynthetic bacteria can be toxic to bacterial activity. The large-scale production of encapsulated particles is complex, and their mass transfer performance is insufficient. Fluid erosion and microbial metabolism can cause the encapsulated particles to rupture and swell, making it difficult to maintain a long service life.

[0004] Therefore, there is an urgent need for a granulation method that can efficiently agglomerate photosynthetic bacteria to overcome the problem of poor aggregation ability of photosynthetic bacteria. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for granulating photosynthetic bacteria using PAC as a carrier. The method provided by the present invention can not only efficiently gather light and cell agglomerates, but also improve the hydrogen production efficiency of photosynthetic bacteria in high-concentration wastewater.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a method for granulating photosynthetic bacteria, wherein the method uses polyaluminium chloride as a core carrier and utilizes hydraulic conditions to granulate the photosynthetic bacteria into agglomerates; the photosynthetic bacteria are pure photosynthetic bacteria;

[0008] The hydraulic conditions are COD concentration, organic load, rising flow rate and hydraulic retention time of wastewater influent.

[0009] Preferably, the pure photosynthetic bacteria is hydrogen-producing Rhodopseudomonas palustris.

[0010] The present invention also provides a method for granulating the above-mentioned photosynthetic bacteria, which specifically comprises the following steps:

[0011] S1. After completely dissolving polyaluminium chloride, the mixture is mixed with the feed wastewater and introduced into the reactor, and the above-mentioned pure photosynthetic bacteria are inoculated;

[0012] S2. The granulation process includes the early stage of floc formation, the particle formation stage and the stable stage after particle formation;

[0013] The hydraulic retention time of the entire granulation process is maintained at 2-5 days, the COD concentration of the influent in the early stage of floc formation is in the range of 500-1500 mg / L, and the organic load is 0.1-0.5 kg COD / m 3 / d, the rising velocity range is 2.0-6.0m / h; the influent COD concentration is adjusted to 1500-3000mg / L during the particle formation period, and the organic load is 0.5-1.0kg COD / m 3 / d, the rising velocity range is 2.0-8.0m / h; after the particles are formed and the stable period, the influent COD concentration is adjusted to 3000-5000mg / L, and the organic load is 0.6-1.5kg COD / m 3 / d; gradually increase the influent COD concentration range after the particles mature.

[0014] Preferably, the polyaluminium chloride is added in an amount of 50-200 mg / L each time, added once every 10 days, added 3-6 times in total, and the total amount added is 0.15-1.2 g / L.

[0015] Preferably, the inoculum amount of photosynthetic bacteria in the method is 1.0-2.0 g / L dry weight.

[0016] Preferably, the COD of the feed sewage is 900-8000 mg / L and the organic load is 0.1-1.5 kg COD / m 3 / d, the rising flow velocity range is 2.0-8.0m / h, and the hydraulic retention time is 2-5d.

[0017] Preferably, the method is carried out in an upflow photobioreactor; the light source of the upflow photobioreactor is a mixture of red light and green light in a ratio of 4:1, the effective volume of the reactor is V≈1L, the diameter d=0.06m, and the cross-sectional area A=0.0028m 2The reactor adopts bottom-in and top-out, with the feed entering from the feed port at the bottom of the reactor and the water outlet located at the top. A peristaltic pump is set to control the feed and discharge flow rate and reflux circulation.

[0018] The invention also provides application of the method in wastewater treatment.

[0019] Preferably, the method promotes the production of hydrogen in wastewater.

[0020] Beneficial effects of the present invention:

[0021] The present invention uses PAC as a carrier and pioneers the technology of granulating pure photosynthetic bacteria into agglomerates and producing hydrogen in high-concentration wastewater for the first time.

[0022] The present invention takes carrier material as the core and utilizes the rising flow rate, water quality composition, hydraulic load, hydraulic retention time and the like of wastewater to realize granulation and agglomeration. The diameter of the final agglomerated particles is mostly 400-800 microns, and the overall granulation time mostly stays at about 80 days.

[0023] The granular form of the hydrogen-producing photosynthetic bacteria in this invention effectively separates the hydraulic retention time (HRT) from the sludge retention time (SRT), and allows for the accumulation of high concentrations of organisms. This overcomes the problem of bacterial colony loss and reduced hydrogen production efficiency caused by the inability to separate the HRT from the SRT in traditional photosynthetic biohydrogen production systems. Furthermore, the granules formed by the photosynthetic bacteria absorb light well, further improving hydrogen production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 The figure is a curve diagram showing the ratio of COD concentration in sewage over time between Comparative Example 1 and Example 3;

[0026] Figure 2 is a curve diagram showing the ratio of the average particle size of photosynthetic bacteria in sewage of Comparative Example 1 and Example 3 as the stages change;

[0027] Figure 3 The sludge volume index SVI in the reactor changes with time in Comparative Example 1 and Example 3 30 Ratio curve graph. DETAILED DESCRIPTION

[0028] The present invention provides a photosynthetic bacteria granulation method using PAC as a carrier, wherein the photosynthetic bacteria is hydrogen-producing Rhodopseudomonas palustris R. palustris, and the bacterial population accounts for 90%.

[0029] The granulation method of photosynthetic bacteria of the present invention is carried out in an upflow photobioreactor (UPBR), wherein the UPBR is made of transparent organic glass, and each reactor has an effective volume V≈1L, a diameter d=0.06m, and a cross-sectional area A=0.0028m 2 . The mixed light of red light (620-780nm) and green light (492-560nm) is used as the light source, with a ratio of 4:1 to ensure the strain advantage of photosynthetic bacteria. The reactor adopts bottom-in and top-out, with the feed entering from the feed port at the bottom of the reactor and the outlet at the top. A peristaltic pump is set to control the inlet and outlet flow rates, and a reflux system is set up, using a peristaltic pump to control the reflux cycle. 1.5L of artificial wastewater is prepared for each reactor every 3 days for supplementary feed. Use a fish tank brush to regularly clean the biofilm attached to the wall every week. The initial inoculation concentration of photosynthetic bacteria is 0.5-2.0g / L dry weight, without any addition in the middle.

[0030] The PAC granulation conditions are as follows: PAC is first dissolved in water, mixed with the feed sewage and fed into the reactor, and inoculated with 1.0-2.0g / L of photosynthetic bacteria by dry weight. The PAC dosage is 50-200mg / L each time, and the dosage time is once every 10 days, for a total of 3-6 times, with a total dosage of 0.15-1.2g / L. The overall rising flow rate range is 2.0-8.0m / h, the influent COD is 900-8000mg / L, and the organic load is 0.1-1.5kg COD / m 3 / d; hydraulic retention time is 2-5d. The granulation process can last for 134 days, with flocs forming around 42-50 days, granules forming around 56-64 days, and mature and stable granules forming after the 80th day.

[0031] This technology uses pure photosynthetic bacteria. It is relatively difficult to achieve granulation and agglomeration in such a pure strain culture system. Furthermore, there is currently no technology or research on granulating and agglomerating pure photosynthetic bacteria using carriers to produce hydrogen in high-concentration wastewater. Other granulation and agglomeration processes for photosynthetic bacteria have all been studied for wastewater treatment and bacterial accumulation, and most of these colonies are due to the combined action of different bacteria to produce granulation and agglomeration. The main purpose of this invention is to produce hydrogen. Not only do the metabolic pathways differ, but the different metabolic pathways also mean that the associated systems are different, which determines the properties and quality of the metabolic products and even the extracellular secretions, resulting in different results. Furthermore, the entire system is a photosynthetic bacteria in an extremely pure environment with almost no other bacteria. The photosynthetic bacteria themselves are highly electronegative and have low extracellular secretions. All of these factors make it very difficult to granulate and agglomerate photosynthetic bacteria in such a system with high strain purity and hydrogen production from wastewater.

[0032] The present invention utilizes a different principle and process for granulation and agglomeration. It utilizes factors such as rising flow rate, water composition, hydraulic load, and hydraulic retention time to achieve granulation and agglomeration. With the carrier material as the core, the final agglomerated particles typically have a diameter of 400-800 microns, and the overall granulation time is typically around 80 days.

[0033] The granular form of the hydrogen-producing photosynthetic bacteria in this invention effectively separates the HRT from the SRT and allows for the accumulation of high concentrations of organisms. This overcomes the problem of bacterial colony loss and reduced hydrogen production efficiency caused by the inability to separate the hydraulic retention time and solid retention time in traditional photosynthetic biohydrogen production systems. Furthermore, the granules formed by the photosynthetic bacteria absorb light well, further improving hydrogen production efficiency.

[0034] The organic load of the present invention refers to the amount of organic matter (measured in chemical oxygen demand (COD)) that can be processed or tolerated per cubic meter of reactor volume in a sewage treatment system per day. The organic load is proportional to the COD concentration of the influent. The higher the COD concentration, the greater the organic load at the same flow rate. Conversely, the lower the COD concentration, the smaller the organic load. Organic load (kg COD / m 3 / d)=water inlet flow (m 3 / day)×COD concentration (g / m 3 ).

[0035] In the present invention, the hydraulic retention time (HRT) refers to the average residence time of the wastewater to be treated in the reactor, which is calculated as tank capacity divided by the influent flow rate. The sludge retention time (SRT) is the sludge age and refers to the average residence time of microbial cells in the aeration tank.

[0036] The wastewater hydrogen production efficiency of the present invention refers to the ability to convert organic matter in the wastewater into hydrogen through biological or chemical methods during the wastewater treatment process. The level of hydrogen production efficiency directly affects the effect of wastewater treatment and the output of hydrogen.

[0037] In order to further illustrate the present invention, the technical solution provided by the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0038] Unless otherwise specified, the production processes, experimental methods or detection methods involved in the embodiments of the present invention are all conventional methods in the prior art, and their names and / or abbreviations are conventional names in the field and are very clear and unambiguous in the relevant fields of use. Those skilled in the art can understand the conventional process steps based on the names and apply the corresponding equipment to implement them according to conventional conditions or the conditions recommended by the manufacturer.

[0039] The hydrogen-producing Rhodopseudomonas palustris of the present invention was purchased from the China General Microbiological Culture Collection Center (strain number: JCM 2524), and ferrosoferric oxide nanoparticles (Fe3O4 NPs) were commercially available (Zhongke Leiming Technology Co., Ltd.).

[0040] The various instruments, equipment, raw materials or reagents used in the embodiments of the present invention are not particularly limited in their sources and are all conventional products that can be purchased through regular commercial channels or prepared according to conventional methods well known to those skilled in the art.

[0041] Example 1 Reactor used for PAC granulation (UPBR)

[0042] Up-flow photobioreactors (UPBR) are made of transparent organic glass. Each reactor has an effective volume of V≈1L, a diameter of d=0.06m, and a cross-sectional area of ​​A=0.0028m. 2 .

[0043] The light source is a mixture of red light (620-780nm) and green light (492-560nm), with a ratio of 4:1, to ensure the strain dominance of photosynthetic bacteria. The reactor adopts bottom-in and top-out, with the feed entering from the feed port at the bottom of the reactor and the outlet at the top. A peristaltic pump is set up to control the inlet and outlet flow rates. A reflux system is set up, and a peristaltic pump is used to control the reflux cycle. 1.5L of artificial wastewater is prepared for each reactor every 3 days for supplementary feed. Use a fish tank brush to regularly clean the biofilm attached to the wall every week. The initial inoculation concentration of photosynthetic bacteria is 0.5-2.0g / L dry weight, without any addition in the middle.

[0044] Example 2 PAC granulation method

[0045] The photosynthetic bacteria is hydrogen-producing Rhodopseudomonas palustris.

[0046] PAC is first dissolved in water and mixed with the feed sewage into the reactor, and inoculated with 1.0-2.0g / L of photosynthetic bacteria. The dosage of PAC is 50-200mg / L each time, and the dosage time is once every 10 days, for a total of 3-6 times, with a total dosage of 0.15-1.2g / L. The overall rising flow rate range is 2.0-8.0m / h, the influent COD is 900-8000mg / L, and the organic load is 0.1-1.5kg COD / m 3 / d; hydraulic retention time is 2-5d. Granulation lasts for 134 days, with flocs forming around 42-50 days, granules forming around 56-64 days, and mature and stable granules forming after the 80th day.

[0047] The overall granulation process is divided into the early stage of floc formation, the particle formation stage and the stabilization stage after particle formation;

[0048] First, in the first stage of floc formation (0-8 days), the influent COD concentration is 500-1000 mg / L and the organic load is 0.1-0.5 kg COD / m 3 / d, the rising velocity is 2-5m / h, and the hydraulic retention time is 2-5d; in the second stage (9-29 days), the influent COD concentration is 1000-1500mg / L, and the organic load is 0.1-0.5kg COD / m 3 / d, rising velocity is 2-6m / h, hydraulic retention time is 2-5d;

[0049] During the particle formation stage, the water conditions are adjusted according to the status of photosynthetic bacteria in the reactor. In the third stage (30-44 days), the influent COD concentration is 1500-2000 mg / L and the organic load is 0.5-0.8 kg COD / m 3 / d, the rising velocity is 2-8m / h, and the hydraulic retention time is 2-5d; in the fourth stage (45-66 days), the influent COD concentration is 2000-2400mg / L, and the organic load is 0.5-0.8kg COD / m 3 / d, the rising velocity is 2-8m / h, and the hydraulic retention time is 2-5d; the fifth stage (67-89 days) is the mature stage, the influent COD concentration is 2400-3000mg / L, and the organic load is 0.8-1.0kg COD / m 3 / d, rising velocity is 2-8m / h, hydraulic retention time is 2-5d;

[0050] Stabilization period after particle formation: the sixth stage (90-103 days), the influent COD concentration is 3000-3500 mg / L, and the organic load is 0.8-1.0 kg COD / m 3 / d, the rising velocity is 2-8m / h, and the hydraulic retention time is 2-5d; in the seventh stage (104-134 days), the influent COD concentration is 3500-5000mg / L, and the organic load is 0.8-1.5kg COD / m 3 / d, the rising flow rate is 2-8m / h, and the hydraulic retention time is 2-5d.

[0051] Example 3 PAC granulation method

[0052] PAC was first dissolved in water, mixed with the feed wastewater, and introduced into the reactor. The photosynthetic bacteria were inoculated at a dry weight of 1.0 g / L. The PAC dosage was 100 mg / L, and the addition interval was once every 10 days for a total of three additions, for a total dosage of 0.3 g / L.

[0053] Early stage of floc formation: In the first stage (0-9 days), the influent COD concentration is maintained at 900 mg / L and the organic load is 0.3 kgCOD / m 3 / d, the rising velocity is 3m / h, and the hydraulic retention time is 3d; the second stage (10-28 days) influent COD concentration is 1500mg / L, and the organic load is 0.5kg COD / m 3 / d, the rising velocity is 5m / h, and the hydraulic retention time is 3d; in the third stage (29-44 days), the influent COD concentration is 1500mg / L, and the organic load is 0.5kg COD / m 3 / d, the rising velocity is 6m / h, and the hydraulic retention time is 3d;

[0054] During the particle formation period, the water conditions are adjusted according to the status of photosynthetic bacteria in the reactor: in the fourth stage (45-63 days), the influent COD concentration is 2000 mg / L and the organic load is 0.7 kg COD / m 3 / d, the rising velocity is 6m / h, and the hydraulic retention time is 3 days. In the fifth stage (64-85 days), the influent COD concentration is 2400mg / L and the organic load is 0.8kg COD / m 3 / d, the rising velocity is 6m / h, and the hydraulic retention time is 3 days. In the sixth stage (86-98 days), the influent COD concentration is 2700mg / L and the organic load is 0.9kg COD / m 3 / d, the rising flow rate is 6m / h, and the hydraulic retention time is 3 days.

[0055] Stabilization period after particle formation: the seventh stage (99-134 days), the influent COD concentration is 3500 mg / L, and the organic load is 1.3 kg COD / m 3 / d, the rising flow rate is 6m / h, and the hydraulic retention time is 3 days.

[0056] Comparative Example 1

[0057] The feed sewage enters the reactor and is inoculated with 1.0 g / L dry weight of photosynthetic bacteria.

[0058] In the first stage (0-9 days), the influent COD concentration is maintained at 900 mg / L and the organic load is 0.3 kg COD / m 3 / d, the rising velocity is 3m / h, and the hydraulic retention time is 3d; the second stage (10-28 days) influent COD concentration is 1500mg / L, and the organic load is 0.5kg COD / m 3 / d, the rising velocity is 5m / h, and the hydraulic retention time is 3d; in the third stage (29-44 days), the influent COD concentration is 1500mg / L, and the organic load is 0.5kg COD / m 3 / d, the rising velocity is 6m / h, and the hydraulic retention time is 3d; in the fourth stage (45-63 days), the influent COD concentration is 2000mg / L, the organic load is 0.7kg COD / m 3 / d, the rising velocity is 6m / h, and the hydraulic retention time is 3 days. In the fifth stage (64-85 days), the influent COD concentration is 2400mg / L and the organic load is 0.8kg COD / m 3 / d, the rising velocity is 6m / h, and the hydraulic retention time is 3 days. In the sixth stage (86-98 days), the influent COD concentration is 2700mg / L and the organic load is 0.9kg COD / m 3 / d, the rising velocity is 6m / h, and the hydraulic retention time is 3 days. In the seventh stage (99-134 days), the influent COD concentration is 3500mg / L and the organic load is 1.3kg COD / m 3 / d, the rising flow rate is 6m / h, and the hydraulic retention time is 3 days.

[0059] Since there is no carrier added, only a single species of photosynthetic bacteria is used. Even if the reactor is kept under the same hydraulic conditions as in Example 3, the photosynthetic bacteria particles formed are still very unstable.

[0060] The results are as follows Figure 1-3As shown, Example 3 forms flocs around 42-50 days, forms granules around 56-64 days, and forms mature and stable granules after 80 days. That is, after the fifth stage (after 80 days), Example 3 forms mature granules with a particle size of 450-700 μm (the dominant particle size range of mature granular sludge is mostly between 450-3000 μm). Correspondingly, after the 80th day, the SVI of the granules 30 The SVI of granular sludge is about 80-100ml / g (the SVI of granular sludge is usually between 80-150ml / g), reaching a stable level. After the 134th day, the COD removal rate reached more than 80%, which was significantly lower than the comparative example. In the comparative example, the overall particle size was lower than that of the embodiment, and the SVI was 30 It is basically lower than 80 ml / g, and the average particle size of Comparative Example 1 is basically below 400 μm.

[0061] The results of this example further show that the present invention uses PAC as a carrier, combined with the adjustment of hydraulic conditions in the reactor, to increase the particle formation time of a single pure species of photosynthetic bacteria in sewage, and the particle formation process of the photosynthetic bacteria is relatively stable.

[0062] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for granulating photosynthetic bacteria, characterized in that: The method uses polyaluminium chloride as a core carrier and utilizes hydraulic conditions to granulate photosynthetic bacteria into agglomerates; the photosynthetic bacteria are pure photosynthetic bacteria; The hydraulic conditions are COD concentration, organic load, rising flow rate and hydraulic retention time of wastewater influent.

2. The method according to claim 1, characterized in that The pure photosynthetic bacteria is hydrogen-producing Rhodopseudomonas palustris.

3. The method for granulating photosynthetic bacteria according to claim 1, characterized in that: The following steps are involved: S1. After completely dissolving polyaluminium chloride, the mixture is mixed with the feed sewage and introduced into a reactor, and the pure photosynthetic bacteria according to claim 2 are inoculated; S2. The granulation process includes the early stage of floc formation, the particle formation stage and the stable stage after particle formation; The hydraulic retention time of the entire granulation process is maintained at 2-5 days, the COD concentration of the influent in the early stage of floc formation is in the range of 500-1500 mg / L, and the organic load is 0.1-0.5 kg COD / m 3 / d, the rising velocity range is 2.0-6.0m / h; the influent COD concentration is adjusted to 1500-3000mg / L during the particle formation period, and the organic load is 0.5-1.0kg COD / m 3 / d, the rising velocity range is 2.0-8.0m / h; after the particles are formed and the stable period, the influent COD concentration is adjusted to 3000-5000mg / L, and the organic load is 0.6-1.5kg COD / m 3 / d; gradually increase the influent COD concentration range after the particles mature.

4. The method according to claim 3, characterized in that The polyaluminium chloride is added in an amount of 50-200 mg / L each time, and is added once every 10 days, for a total of 3-6 times, with a total addition amount of 0.15-1.2 g / L.

5. The method according to claim 3, characterized in that: In the method, the inoculum amount of the photosynthetic bacteria is 1.0-2.0 g / L of dry weight.

6. The method according to claim 3, characterized in that: The COD of the feed sewage is 900-8000 mg / L, and the organic load is 0.1-1.5 kg COD / m 3 / d, the rising flow velocity range is 2.0-8.0m / h, and the hydraulic retention time is 2-5d.

7. The method according to claim 3, characterized in that The method is carried out in an upflow photobioreactor; the light source of the upflow photobioreactor is a mixture of red light and green light in a ratio of 4:1, the effective volume of the reactor is V≈1L, the diameter d=0.06m, and the cross-sectional area A=0.0028m 2 The reactor adopts bottom-in and top-out, with the feed entering from the feed port at the bottom of the reactor and the water outlet located at the top. A peristaltic pump is set to control the feed and discharge flow rate and reflux circulation.

8. Use of the method according to any one of claims 1 to 2 or the method according to claim 3 in wastewater treatment.

9. The application according to claim 8, characterized in that: The method promotes the production of hydrogen in wastewater.

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