Patent Application
20140197099
This invention relates to treatment beds, facilities, and methods for treating wastewater, and especially high strength wastewater.
High strength wastewater, i.e., wastewater with a biochemical oxygen demand (BOD) of at least 300 mg O2/l or greater, as well as wastewater with a chemical oxygen demand (COD) of at least 500 mg O2/l, presents various treatment challenges. Such wastewater is produced, for example, by food processing plants, dairy farms and restaurants. Wastewater from the processing of meat and poultry are particularly challenging due to their characteristic elevated levels of fat and various colloidal and suspended solids resulting from the slaughtering and carcass rinsing processes. Turkey processing wastewater contains dissolved organics, suspended solids in the form of proteins, blood residue, grease and fats along with cleaning and sanitizing agents.
Although such wastewater can be effectively treated using sand bioreactors wherein a “biofilm” of microorganisms forms on the sand particles, the high strength wastewater tends to clog such filters at a rate which renders them impractical for large scale use. Primary causative agents of clogging are believed to include BOD loading rates, suspended solids and bacteria.
The clogging problem has been addressed using layered granular filter media of varying coarseness. In one example, layers of pea gravel and coarse sand were used as a pre-filter atop a fine sand bioreactor. While layered sand and gravel filter media have been shown effective at preventing or reducing the rate of clogging, such filters come with certain disadvantages, cost being at the forefront. Various suitable grades of sand and gravel are not naturally available, they must be prepared (i.e., screened, washed) and then transported in bulk to the site of the treatment facility. As can be appreciated, for large scale operations the filter media cost alone may be prohibitive. There is clearly a need for a treatment bed which can effectively treat high strength wastewater
The invention concerns a method of treating high strength wastewater. In one example embodiment, the method comprises:
By way of example, the textile leaves are arranged randomly atop one another. The textile leaves may have a rectangular shape. The first layer may be between about 10 cm thick and about 60 cm thick. In a particular example embodiment, the first layer is about 30 cm thick. The textile leaves may comprise a woven material or a non-woven material. In a specific example the textile leaves comprise felt. The felt may be selected from the group consisting of polyester, polypropylene, nylon and combinations thereof.
The granular material may comprise sand. The sand may have an effective size from about 0.25 mm to about 1.0 mm and a uniformity coefficient between about 1.0 and about 4.0. In a particular example embodiment, the sand has an effective size of about 0.3 mm and a uniformity coefficient of about 4.0.
The invention also encompasses a bed for treating wastewater. In one example embodiment, the bed comprises a layer of first granular material. A layer of treatment material is positioned above the layer of first granular material. At least one distribution conduit is positioned above the layer of treatment material for discharging the waste water onto the layer of treatment material At least one drain conduit positioned beneath the layer of first granular material. The at least one drain conduit collects the wastewater and conducts it away from the layers. A water impermeable layer is positioned beneath the at least one drain conduit. In one example embodiment the first granular material comprises fine sand. The treatment material may comprise pea gravel. In another example embodiment, the treatment material comprises a plurality to textile leaves. The textile leaves may be arranged randomly atop one another. The textile leaves may have a rectangular shape. The textile leaves may comprise a woven material or a non-woven material. In a specific example embodiment, the textile leaves comprise felt. The felt may be selected from the group consisting of polyester, polypropylene, nylon and combinations thereof.
By way of example, the water impermeable layer may comprise a waterproof liner. A layer of sand may be positioned beneath the waterproof liner.
The example embodiment may further comprise a layer of second granular material positioned between the layer of first granular material and the at least one drain conduit. In a particular example, the layer of second granular material comprises wash rock. The example embodiment may further comprise a layer of third granular material positioned between the layer of second granular material and the layer of first granular material. In a particular example embodiment, the layer of third granular material comprises pea gravel.
By way of example, the invention may further comprise at least one branch conduit positioned between the layer of first granular material and the distribution conduit. In this example, at least one riser conduit extends between and provides fluid communication between the at least one branch conduit and the at least one distribution conduit. This example may further comprise a supply header positioned between the layer of first granular material and the at least one distribution conduit. The supply header is in fluid communication with a source of the wastewater. The at least one branch conduit is in fluid communication with the supply header in this example.
In another example embodiment, the invention further comprises a valve positioned between the riser conduit and the at least one distribution conduit for controlling flow of the wastewater therethrough. The valve may be a solenoid valve. The example embodiment may further comprise an indexing valve positioned between the riser conduit and the at least one distribution conduit.
In another example embodiment, a layer of fourth granular material is positioned between the treatment layer and the layer of first granular material. In a specific example embodiment, the layer of fourth granular material comprises coarse sand. A fifth granular material may be positioned above the layer of treatment material by way of example. In a specific example, the fifth granular material comprises pea gravel.
In another example embodiment of a bed for treating wastewater, the bed comprises a drain header and a plurality of drain conduits in fluid communication with the drain header. A supply header is positioned above the drain header and a plurality of branch conduits are in fluid communication with the supply header. The branch conduits are positioned above the drain header. A plurality of riser conduits are included, each one of the riser conduits extending from a respective one of the branch conduits. A plurality of manifolds are positioned above the branch lines, each one of the manifolds being in fluid communication with a respective one of the riser conduits. A plurality of distribution conduits are positioned above the branch lines. At least two of the distribution conduits are in fluid communication with each of the manifolds. The distribution conduits discharge the wastewater therefrom. A layer of first granular material is positioned between the drain conduits and the distribution conduits and a layer of treatment material is positioned between the layer of first granular material and the distribution conduits.
Another example embodiment further comprises a plurality of valves. Each of the valves is positioned between one of the riser conduits and one of the manifolds for controlling flow of the wastewater between the riser conduits and the manifolds. The valves may be remotely controllable valves. In a specific example embodiment the valves are solenoid valves. The example embodiment may further comprise a plurality of indexing valves. Each of the indexing valves is positioned between one of the valves and one of the manifolds for directing flow of the wastewater into the manifolds.
By way of example, the first granular material may comprise fine sand. The treatment material may comprise pea gravel. In another example embodiment, the treatment material comprises a plurality of textile leaves. The textile leaves may be arranged randomly atop one another. The textile leaves may have a rectangular shape. The textile leaves may comprise a woven material or a non-woven material. In a particular example embodiment, the textile leaves comprise felt. The felt may be selected from the group consisting of polyester, polypropylene, nylon and combinations thereof.
In a further example embodiment, a waterproof liner is positioned beneath the drain conduits. A layer of sand may be positioned beneath the waterproof liner.
Another example embodiment comprises a layer of second granular material positioned between the layer of first granular material and the drain conduits. The layer of second granular material may comprise wash rock. By way of further example, an embodiment may comprise a layer of third granular material positioned between the layer of second granular material and the layer of first granular material. In a specific embodiment, the layer of third granular material comprises pea gravel. Another example embodiment may further comprise a layer of fourth granular material positioned between the treatment layer and the layer of first granular material. In a specific example embodiment, the layer of fourth granular material comprises coarse sand. Another example embodiment comprises a fifth granular material positioned between the manifolds and the layer of treatment material. The fifth granular material comprises pea gravel in a specific example embodiment.
In an example embodiment, the distribution conduits have a plurality of holes therein for discharge of the wastewater. The holes may be spaced apart from one another at intervals of about 1 foot. Furthermore, in this example embodiment, the drain conduits may have a plurality of slots therein, the slots for admitting wastewater to the drain conduits for removal from the bed.
By way of example, the invention may further comprise a storage tank for holding the wastewater. This example embodiment may also comprise a pump in fluid communication with the storage tank and the supply header for pumping the wastewater from the tank to the supply header. In a further example embodiment, a pump is in fluid communication with the drain header, the pump for pumping the wastewater from the drain header and out of the bed.
In one example embodiment of the invention, the bed is located within an excavation site.
The invention further encompasses a facility for wastewater treatment comprising a plurality of beds. In example embodiments, the facility may further comprise a storage tank for holding the wastewater and a first piping network providing fluid communication between the storage tank and the supply header of each of the beds. A second piping network may be used to provide fluid communication between the drain headers of each of the beds.
In another example embodiment, the invention may further comprise a first pump positioned between the storage tank and the first piping network for pumping the wastewater from the storage tank into the supply headers of each of the beds. A second pump may be in fluid communication with the second piping network for pumping the wastewater from the drain headers of each of the beds.
The invention further encompasses a method of operating the facility. In one example embodiment, the method comprises:
The method of operating the facility may further comprise, by way of example, flowing a predetermined amount of the wastewater to each one of the beds in turn, one after another, for all of the plurality of beds.
Drain headers 16 in each of the beds 12 are in fluid communication with a second piping network 26. After treatment in each bed 12, wastewater effluent is collected from the drain headers 16 and conducted through the second piping network 26 for eventual discharge to the local watershed 28, in this example, a nearby river. Additional devices may be interposed between the beds 12 and the watershed. In this example facility 10, each bed 12 also includes a sump compartment 30 in fluid communication with the drain header 16 and the second piping network 26. Each sump compartment provides access to the wastewater effluent from its respective bed 12, allowing effluent samples to be taken to evaluate the treatment performance of each bed. A second pump 32 may also be employed to pump effluent to an effluent treatment station 34 where the total effluent from the facility 10 may be analyzed for water quality as well as receive additional treatment such as ultraviolet sterilization and/or nutrient removal before discharge. A third pump 36 may be used to pump the effluent from the station 34 for ultimate discharge.
As shown in
As shown in
The supply header 14 and its associated branch conduits 48 are supported on the pea gravel layer 70 along with a layer 72 of fine sand of about 18 inches thick. The sand of the fine sand layer 72 ranges in size from about 0.3 mm to about 1.18 mm. A layer 74 of coarse sand of from about 4 inches to about 6 inches thick sits above the fine sand layer 72, the coarse sand of layer 74 have a size ranging between about 1.18 mm to about 4.75 mm.
A layer 76 of treatment material is positioned between the coarse sand layer 74 and the distribution conduits 64. In one example bed 12, the treatment material layer 76 comprises a layer of pea gravel of about 6 inches thick, the pea gravel ranging in size from about ¼inch to about ½ inch. In another example embodiment, the treatment layer 76 comprises a plurality of textile leaves 78. Textile leaves 78 may have a polygonal shape, for example, rectangular, and dimensions of about 2 inches by 4 inches and about ⅛ inch to about ¼ inches thick. Other shapes and sizes are also feasible, and it is believed that textile leaves from about one half to double the size noted above will be effective. The textile leaves 78 may be formed of a woven material, but are advantageously formed of non-woven material such as felt. The felt may comprise synthetic fibers such as polyester, polypropylene, nylon and combinations thereof. While natural fibers such as cotton and wool are also feasible, the synthetic fibers are advantageous because they do not decompose like the natural fibers. When the treatment layer 76 is formed of textile leaves 78, it, and the distribution conduits 64 may be covered by a finishing layer 80 of pea gravel. The valves 52 and indexing valves 56 remain exposed for ease of servicing along with the manifolds 62.
A particular example experimental test facility 10 was constructed. The facility 10 occupied a 4 acre site which included twelve beds 12, each bed measuring 82 feet by 180 feet. The storage tank 18 had a working volume of 80,000 gallons and the pump 24 had a flow rate of 200 gallons per minute. The pump 24 supplied wastewater influent to the beds at a pressure of about 44 psig. Each bed had twenty remotely controlled valves 52 (KRain 150 Series Solenoid Valve) which controlled the flow of wastewater influent to twenty remotely controlled indexing valves 56 (Fimco 6 Outlet Indexing Valve). Each valve 52 had a maximum flow rate of 50 gallons per minute. Each indexing valve 56 had six outlets 60, and each outlet fed a respective manifold 62. Each manifold 62 was in fluid communication with six distribution conduits 64 for a total of 720 distribution conduits per bed and 8,640 total among the twelve beds 12.
The first piping network 20 which supplies wastewater influent to the beds 12 comprised PVC pipe having a diameter of 4 inches. The second piping network 26 which conducts the wastewater effluent from the beds 12 after treatment comprised PVC pipe having a diameter of 8 inches. The second pump 32 had a capacity of 200 gallons per minute and operated at 14 psig. The discharge pump 36 had a capacity of 200 gallons per minute and operated at 34 psig. Drain conduits 40 comprised PVC pipe having a diameter of 4 inches and slots of ¼inches in width spaced on 6 inch centers. Riser conduits 50 comprised PVC pipe having a diameter of 1½ inches. Manifolds 62 comprised PVC pipe having a diameter of 1½ inches, and distribution conduits 64 comprised PVC pipe having a diameter of 1 inch with discharge holes 66 separated on one foot centers as noted.
In experimental test facility 10, each bed comprised a layer of fine leveling sand 46 2 inches thick, a 30 mil PVC water impermeable liner 44, a 6 inch thick layer of wash rock 68, a two inch layer of pea gravel 70, an 18 inch thick fine sand layer 72, a six inch coarse sand layer 74, a six inch thick treatment layer 76 of pea gravel and a finishing layer 80, also of pea gravel.
In operation of experimental test facility 10, valves 52 are opened in groups of four at a time in a first bed 12 for a dose duration of 50 seconds. After all valves 52 in the first bed 12 have been opened once in turn, the cycle starts again, but the indexing valve 56 is actuated, resulting in the wastewater influent being directed to a different manifold 62 and thus to different distribution conduits 64. This cycle is repeated six times for the first bed (there being six manifolds per valve) such that all of the distribution conduits 64 have dosed the first bed 12 for 50 seconds. This same flow regime is then repeated for each bed 12 in turn. The facility 10 with its twelve beds 12 is capable of 3 full doses per bed per day of operation.
As shown in
The wastewater, now “effluent” passes through slots 42 and is collected in the drain conduits 40 shown in
Operation of the system as described above has shown that the system performance exceeds limits of BOD<10, TSS<12 (Total Suspended Solids), Ammonia<1 Summer, Ammonia<3 Winter.
Use of the treatment material layer 76 of pea gravel in the experimental test facility 10 has proven effective at mitigating clogging of the beds 12 when processing high strength wastewater (wastewater having a BOD greater than 300). However, based upon comparative laboratory tests it is also expected that textile leaves 78 may be substituted for the pea gravel in the treatment material layer 76 of beds 12. As shown in
In the test, the performance of the sand/textile leaf bioreactor column 82 was compared with that of a sand/gravel bioreactor column 90, shown in
In the test, pairs of each column type 82 and 90 were operated under the same conditions and parameters as described in Table 1, the only difference being a slightly smaller surface area available for biofilm formation for bioreactor columns 82 having the textile leaf layer 88. This testing regime permitted a head to head comparison between sand/gravel columns 90 and columns 82 using the textile leaf layer.
The operation and performance of the bioreactors 82 and 90 are described in detail below for treatment of turkey processing wastewater.
Grab samples of turkey processing wastewater were retrieved from a discharge pipe following a grease trap located in a storage pond at Whitewater Processing Inc., Harrison, Ohio. Samples were taken during the day shift at random dates and times every 3 to 4 weeks and stored in the laboratory at 4° C. until used in the experiments. The composition of wastewater varied with the production activities in the turkey processing facility. The wastewater was applied on bioreactor columns 82 and 90 using a programmable, time controlled pump at the hydraulic loading rate of 66 L/m2/day (1.63 gal/ft2/day) in 72 timed daily doses. The columns 82 and 90 were operated indoors at 22±2° C. Wastewater influent and effluent samples were analyzed once a month for BOD5 and COD using the standard methods (APHA. 1998. Standard Methods for the Examination of Water and Wastewater. 20th ed. American Public Health Association, Washington, D.C., hereby incorporated by reference herein).
The clogging of columns 82 and 90 was estimated with the procedure described by Xi and others (Xi, J., K. M. Mancl and O. H. Tuovinen. 2005. Carbon Transformation During Sand Filtration of Cheese Processing Wastewater. Applied Engineering in Agriculture. 2(2): 271-274, hereby incorporated by reference herein). The volume of the daily dose was applied in one single dose to the columns 82 and 90. The clogging index (CI) was calculated as the ratio of the effluent volume collected in the first 90 min over the daily dosing volume applied to the columns following a rest period of 24 h.
The associations between the BOD5 and COD removal efficiencies, different media types and bioreactor run times over the entire experimental period were analyzed using one-way ANOVA with a 95% confidence interval using Minitab 15 Statistical Software.
The turkey processing wastewater was treated with the sand/gravel bioreactors 90 and sand/textile bioreactors 82 at a loading rate of 66 L/m2/day (1.63 gal/ft2/day). The influent BOD5 ranged from 460 to 2260 mg O2/l and the COD values ranged from 840 to 2260 mg O2/l (Table 2). The effluent from both the sand/gravel and the sand/textile bioreactor columns 90 and 82 had BOD5 values of 10 mg/l or less, with just one exception. COD effluent values ranged from 4 to 70 mg O2/l. The efficiencies of BOD5 and COD removal remained constant throughout the period of study. The corresponding BOD5 and COD removal efficiencies were >99% and >95%, respectively, even after over 26 months of column operation. Thus all of the bioreactors demonstrated steady, uninterrupted treatment efficiency.
The BOD5 and COD results obtained for sand/gravel bioreactor 90 and sand/textile bioreactor 82 were analyzed using ANOVA. The differences in BOD5 and COD removal between the two different treatment matrices were statistically not significant (P>0.05).
Clogging was not a problem in these experiments. The pea gravel layer 100 and textile leaf layer 88 each acted as a sieve to trap suspended solids and fat globules. Therefore, the typical approaches of effluent recycling and separation of solids from the turkey processing wastewater were not needed allowing for extended filter operation without clogging. Biofilm communities on the surface of pea gravel in layer 100 and textile leaves in layer 88 can act upon trapped organic matter but the major biodegradation activity is associated with the biofilm in the sand layers 86, 96 and 98. Previous work has demonstrated that the pea gravel layer 100 extends the useful life of bioreactor operation as compared to bioreactors without pea gravel. By placing the coarse sand/pea gravel layers 98 and 100 or textile leaf layer 88 on top, no additional land area is required for a pretreatment module as these layers overlaid the final treatment unit of fine sand.
After 15 months of column operation, clogging was measured using the aforementioned procedure developed by Xi and others. For no clogging, the clogging index (CI) is 1.0, and complete clogging has a CI of 0.0. Test results showed that the sand/gravel bioreactor columns 90 had CI values of 0.64 and 0.69. The CI values for the sand/textile bioreactor columns 82 were slightly more clogged at 0.53 and 0.60. In spite of the slight difference in the amount of clogging in sand/gravel and sand/textile bioreactors, the BOD5 and COD removal efficiencies were comparable.
Clogging test were repeated after 19 months of column operation. The CI values were 0.66 and 0.67 for sand/gravel columns 90 and 0.61 and 0.65 for the sand/textile columns 82. No significant differences in the CI values were discerned between the sand/gravel and sand/textile columns (Table 3).
The clogging tests were performed to assess the condition and treatment capability of the bioreactors. A CI value of 1 indicates no clogging. The clogging test results obtained showed a reasonable amount of clogging (˜35%) for all the bioreactors. Wastewater treatment efficiency showed no change as the removal of >99% BOD5 and >95% COD was sustained for all columns for the entire course. The results suggest that partial clogging did not have a negative effect on the treatment of wastewater. In fact, it is possible that partial clogging may enhance the treatment by increasing the contact time of waste with the biofilm.
In this test, textile media for pretreatment was compared to layers of coarse sand and pea gravel. COD and BOD5 removal and filter clogging were evaluated. Results from this test show that both sand/gravel and sand/textile bioreactors have excellent treatment capability for the removal of organic matter that was measured as BOD5 and COD. The effluent obtained from these bioreactors was of high quality in terms of organic matter removal. Sand/textile bioreactors will be a better option where access to the site is difficult because textile leaves are lighter and can be transported easily. Should the need arise, replacing the textile leaf layer will be easier as compared to replacing a layer of a sand/gravel bioreactor.
The presence of visible turkey fat in the wastewater did not cause problems in bioreactor column operation as demonstrated from the high steady removal of organic loading and the lack of clogging. Cleaning, back washing, raking, or replacing of top gravel or textile layers was not necessary to maintain bioreactor column operation. The data obtained from this test indicate that sand bioreactors having a textile leaf treatment layer can be effectively used for the treatment of high strength wastewater and the treated wastewater can achieve BOD5 values to meet strict effluent discharge limits.
This application is based upon and claims priority to U.S. Provisional Application No. 61/751,535 filed Jan. 11, 2013, which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61751535 | Jan 2013 | US |
