The purpose of this project: is to evaluate the use of an Aerated Fluidized Bed Reactor (aerated-FBR) Constructed Wetland Treatment (CWT) for reclaiming livestock wastewater effluent (LWE). Study will look into reclaiming wastewater from diary and swine farms, both are a major contributor to LWE generated in New Jersey (NJ). A two-step approach is proposed whereby (a.) ammonium-nitrogen (NH4-N) and orthophosphate (PO4-P) are extracted by precipitation of struvite (MgNH4PO4*6H2O) using a aerated-FBR; (b.) nitrate-nitrogen (NO3-N), total suspended solids (TSS) and dissolved organic carbon (DOC) are removed by CWT to produce irrigation waters. The aerated-FBR-CWT method will reduce livestock farm operation costs by recycling nutrients as struvite fertilizer and reclaiming LWE as irrigation water
Environmental challenges of LWE:
Dairy cows generate ~60 gallon/day-animal (gal/d-a) of LWE, while swine generates ~10 gal/d-a, with high concentrations of dissolved nutrients and other components. LWE is the sum of flush effluents from milking parlors, yards and stalls which is stored in wastewater lagoons. High levels of PO4-P, NH4-N and TSS generate harmful BOD, and decompose into contaminants such as NO3-N. The common treatment practice is applying LWE onto fields as fertilizer using cannon sprinklers or spraying vehicles. LWE can impact agricultural soil, groundwater and surface water, and the odor can be a nuisance. The high NH4-N is converted into NO3-N by nitrification, resulting in nitrate contamination of groundwater through leaching. Particulate OP is susceptible to aeolian transport which introduces OP to open water sources and contributes to eutrophication. The BOD and TSS content of LWE, along with a high bacterial count, requires separation from freshwater, and therefore storage in lagoons and tanks with no direct leaching pathway to groundwater or surface water
Sustainability issues being addressed:
Many livestock farms also grow a portion of their livestock feeding crops on site, and maintaining soil fertility is a significant component of operation costs. Spraying LWE over crop fields is an acceptable, but costly approach to waste disposal. In addition to environmental problems, the spraying method also presents agronomic disadvantages. Non-composted LWE is a lower-grade fertilizer compared to compost and mineral fertilizers, as it is less stable and provides imprecise nutrient application. The higher volatility and bioavailability of NH4-N, compared to OP in soils often results in excess P application to meet the crop N demand, or the need for additional fertilizer. In addition, excess water is applied via spraying. Therefore, LWE spraying has low water preservation and fertilizer application efficiencies. aerated-FBR-CWT reclaims key nutrients, PO4-P and NH4-N, as struvite fertilizer and produces treated water for targeted irrigation. The 1:1:1 ratio of N:P:Mg distinguishes struvite as a PO4-P and Mg source, compared to livestock compost that has high N volatility and low Mg content. Application of Mg benefits the soil structure, reducing swelling and the exchangeable sodium ratio in clay soils. Production of struvite combined with irrigation water maintains the regional mass-balance of these resources as less fertilizer and water are required from outside the farm resource-cycle.
Reclamation of LWE:
Preliminary work used a bench-scale aerated-FBR to reclaim struvite from swine and dairy LWE. Results showed 64% OP removal for dairy and 97% OP removal for swine. P removal was achieved through Mg addition and increasing the pH to 9. Solids collected from AFBR were mostly struvite (97-55%), mixed with calcite (CaCO3). Use of CWT to treat wastewater is well established with two major treatment concepts of submerged and open water flow, with variations depending on local climate, fauna and biota. The research group is currently working on testing an adaptation to dairy CWT treatment that aims to reduce both TSS and BOD levels in LWE to meet 30 mg/L discharge standards.
Economic impact of aerated-FBR-CWT:
Treatment will inflict some short-term costs on dairy producers ($47.5/a-y) and will save costs for swine producers ($2/a-y). However, considering the long-term economic impact, it is reasonable to expect that further development of AFBR-CWT and its application will reduce operation costs over time.
Direct impact breakdown:
LWE treated by AFBR-CWT with sufficient TSS and BOD reduction can be integrated into irrigation water cycles, with the ability to adopt conservative irrigation methods, unlike LWE spraying. Operational costs for treatment are $8/animal-year (a-y) and $80/a-y for swine and dairy. Nutrient recovery gain is estimated at $1/a-y for swine and $2.5/a-y for dairy, while gains from water reclamation are estimated at $1/a-y and $5/a-y from corn silage production for swine and dairy respectively. Eliminating spraying costs are $8/a-y and $25/a-y for swine and dairy.
Indirect impact factors of aerated-FBR-CWT application:
Reduce loss of soil fertility due to excessive P accumulation in soils; reducing environmental nuisance of livestock farms; decrease exposure by livestock producers to costs of emergency LWE disposal in heavy rain seasons and by spiked feeding costs in drought years.
1. Assessment of LWE properties to determine aerated-FBR-CWT requirements:1. Assessment of LWE properties to determine AFBR-CWT requirements:The study locations: Fulper farm, Hunterdon County and Rutgers New Brunswick (RU-NB) animal science farm, NJ. An on-site study will characterize the LWE, including TSS, BOD and nutrient content, in order to design the most suitable CWT layout.
2. Produce struvite fertilizer for crop production by recycling nutrients from LWE:The aerated-FBR will be used to recover OP and NH4-N from LWE by induced precipitation of struvite, to be recycled on-site as fertilizer. The measurement of success for aerated-FBR treatment is >70% PO4-P removed with >60% struvite content in the precipitated salt for dairy LWE and >90% PO4-P removed with >90% struvite content in the precipitated salt for swine LWE.
3. Implement CWT to meet primary treatment water discharge requirements:While traditional LWE treatment does not contribute to farm water balance, CWT can reclaim the bulk of effluent water for irrigation by removing remaining nutrients and contaminants. The current standard for primary effluent treatment is 30/30 mg/L BOD/TSS. CWT will need to reduce the BOD/TSS concentrations accordingly if the water is to be reused. The assumption is that if a consistent and stable CWT system can be constructed to remove nutrients, BOD/TSS requirements can be attained by expanding the system in a series of CWT structures. The measurement of success for CWT is therefore meeting the effluent discharge requirements, making treated LWE usable for crop irrigation.
4. Industry outreach: Dissemination: The aerated-FBR-CWT method will be promoted by hosting on-site tours of the treatment facility for local producers, high school students and researchers at the RU-NB farm site, and by attending agronomy expo events.
5. STEM outreach: Undergraduate student research:To encourage more students to engage in STEM-related sustainability research, undergraduate students will be directly involved in the project. These students will be supported by National Science Foundation (NSF) Research Experiences for Undergraduates (REU), and Garden State-Louis Stokes Alliances for Minority Participation (GS-LSAMP) programs at Rutgers University-Newark (RU-N). The students will conduct on-site research at the RU-NB farm, compile reports, and present results at local conferences.
6. Scientific and public outreach: Publication and presentation:Findings will be published in scientific peer-reviewed journals as part of Mr. Rabinovich’s dissertation. Results will be presented at national meetings, such as the American Chemical Society (ACS) meetings. Presentations at local events will inform the general public.
In order to meet the project objectives the performance of the two-step aerated-FBR-CWT approach, applying struvite recovery followed by contaminant removal for LWE, needs to be assessed. The two-step treatment method will use aerated-FBR-CWT applied in a continuous flow canal system. LWE is pumped into the aerated-FBR and from there, the outflow will be directed into the CWT canal for primary wastewater treatment.
The system will be constructed on Fulper farm for the first testing period, then relocated to the New Jersey Agricultural Experiment Station (NJAES) located at RU-NB for the second testing period. These two sites were chosen as they are good representative models for a small-scale farm operation. Fulper farm has ~200 milking cows and a 750,000-gallon lagoon for LWE storage, while RU-NB has a ~60 sow farm and is accessible to the public as a state-owned university facility. The RU-NB dairy farm was not chosen as it is too small and does not have a LWE lagoon system. In deciding on placement season for the aerated-FBR-CWT at both farm sites, consideration is given to these facilities’ layouts and to seasonal environmental conditions. As such, the experiment at Fulper farm cannot take place December-April due to lagoon freeze, while RU-NB cannot take place in March-September due to over-filling of rainwaters.
Lagoon wastewater effluent (LWE) includes all the liquids generated in the farm yard, stalls and milking parlor by livestock and maintenance procedures. These are drained to a separation pool with a two-chamber cell connected by an overflow canal. The bulk of the solids sink to the bottom of the first cell, while effluent overflows to the secondary cell. From there the effluent is drained into the storage lagoon. Assessment of the LWE chemical properties will be done to determine LWE treatment requirements using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Ultraviolet Visual (UV-Vis) spectroscopy, quantifying major ions and dissolved nutrient content. Preliminary assessment of LWE at Fulper and RU-NB farms, acquired using colorimetric analysis (Hach DR 3900) and ICP-OES (Agilent 5110), are presented in Table 1.
LWE nutrient removal using aerated-FBR:
Nutrient recovery is facilitated by the precipitation of struvite from LWE to remove up to 98% OP from the effluent. The struvite mineral is made up of Mg(2+), PO4(3-) and NH4(+) ions in a 1:1:1 ratio. Struvite precipitation can be described by the following reaction:
Mg2+ + NH4+ + PO43- + 6H2O = MgNH4PO4*6H2O
Struvite has a low solubility product, logKsp= -13.26, indicating that mineral dissolution is low, contributing to its properties as a slow-release fertilizer. For typical LWE both the Mg (~0.01M) and OP (~0.0015 M) concentrations tend to be consistently lower than NH4-N (~0.033M), making them the limiting factor for struvite formation. Another factor affecting struvite formation is the high calcium concentration of LWE that can promote the formation of other OP minerals such as hydroxylapatite (Ca5(PO4)3OH). This results in an inferior fertilizer with regard to OP availability in soil solution due to the extremely low solubility of hydroxylapatite (log Ksp= -44.33) compared to struvite. Adding supplementary Mg to the effluent as magnesium chloride hexahydrate (MgCl2*6H2O) can promote the formation of mostly struvite salts and reduce the apatite content, while adding potassium OP (K2HPO4) could remove excess NH4-N. The rate of precipitation is also driven by pH, where the reaction time, represented as hydraulic retention time (HRT), is the time required for nutrient removal to reach treatment goals at pH 9. The pH of lagoon LWE ranges from 6.5-8, depending on the depth of the lagoon, LWE type and the time of year. To meet the pH 9 requirements in the aerated-FBR, the pH can be increased by carbon dioxide stripping with aeration and the addition of sodium hydroxide (NaOH) titration.
The aerated-FBR is a small field size reactor with a 40-liter volume. The reactor will be housed near the LWE source in the farm operational area, receiving power supply from the nearby farm facility. A peristaltic metering pump (Masterflex) will be used to load LWE into the reactor. At an inflow rate of 10 gallons/hour the AFBR will have ~60 minutes HRT allowing enough time for precipitation, and the ability to treat 240 gallons of LWE per day. The main chamber will generate the bulk of struvite crystallization as incoming LWE becomes saturated and interacts with struvite colloids. For initial struvite nucleation, 0.1g/L (4 g/reactor-run) of fine-grained struvite powder will be added as seeding for struvite crystal nucleation, acting as a template for crystal growth and precipitation. In order to supersaturate struvite in the LWE, alkaline conditions are required. Aeration at a 42 cu.ft. air per cu.ft. LWE-hour will be used to raise pH up to ~pH 8.5 by CO2 stripping, using a linear diaphragm air compressor (Thomas). To further induce precipitation, and maximize removal of NH4-N, 0.25 N NaOH, 1 M MgCl2*6H2O and/or 1 M K2HPO4 solutions will be added using three Fisher brand peristaltic pumps based on experimental treatment.
The pH will be measured in the reaction chamber using an inflow Cole-Palmer pH electrode. The main chamber has an overhead mixer (Arrow 1200) with a PTFE coated mixer shaft and a 4-inch blade, generating a circular flow to promote crystallization and generate suspended particles, preventing struvite sedimentation on the reactor walls. A narrow-slit passage connects the continuous flow stirred-tank reactor chamber (CSTR) and fluidized bed (FB) chambers in the aerated-FBR. The FB conical prism reduces the LWE flux from an average of 20 cm/min at the entry slit, to an average 2 cm/min at the point of exit. As the struvite particle velocity slows, they cease to be suspended and vertical settling transports crystals downward. This circular motion separates the salt solids from the effluent leaving the reactor, allowing the crystals to undergo an extended growth period. When the crystals reach a reasonable particle size (~0.125 inches), they can be easily separated from smaller particles by reducing the mixing speed and collection from the valve at the reactor base. The fluidized bed formation is tuned by adjusting the mixing speed of the overhead stirrer. Minerals harvested from the AFBR will be air-dried in incubation at 95 oF for 72h and analyzed with X-ray diffraction (XRD; Bruker, D8) and ICP-OES (Agilent, 5110) to determine their elemental and nutrient contents. Additional analysis using simultaneous thermal analysis (STA) and evolved gas analysis (EGA) will evaluate the thermal stability of fertilizer solids collected from aerated-FBR (Netzsch Perseus STA 449 F3, coupled with Bruker Alpha FTIR). Such analysis will compare thermodynamic factors such as enthalpy of ammonia emission and mass loss rates between collected struvite and commercial fertilizers.
LWE primary treatment with CWT:
CWT allows microbial, flora, chemical and mechanical processes to remove contaminants from LWE. Our CWT system will use a three-cell setting, based on the Environmental Protection Agency (EPA) CWT manual, combined with recommendations for LWE-CWT tested by Agricultural Research Organization (ARO) in Israel, for medium sized dairy farms (up to 1000 milking cows). The CWT cells are series in a column of canals and consist of Free Water Surface (FWS) and Vegetated Submerged Bed (VSB) cells settings (Figure-2). The HRT requirement for each cell is two days, for a total HRT of six days. The total LWE mass in the CWT is the total volume times the cell porosity. For our assessment, we will use recommended porosity values of 0.7, 0.3 and 1 for the FWS (emerged plants), VSB (submerged flow with plant cover) and open FWS (submerged plants). Our three-cell canal is 1.2 m (4 ft) wide, 0.6 m (2 ft) deep and 12 m (40 ft) long with a 1% sloped base leaning in the flow direction. The total pore volume of the CWT canal is ~5800 L, and with a LWE intake of 908 L/day (240 gallons) coming from the aerated-FBR, will meet the 6 day HRT needs. The CWT cells will be made from 60 mil PVC fabric sheets nested in a two by four wood and plywood frame for structural support, placed on an operational space near the AFBR.
The first CWT cell (FWS) is fully vegetated with a 6-inch turf soil bed to support emerging water plants such as common reeds (Phragmites) and Sweetflag (Acorus americanus), and populated with floating lemna plants (Lemna minor) and emerging water plants. Lemna cover of the water surface creates mildly anaerobic conditions needed to promote flocculation, sedimentation, adsorption and the anaerobic reactions that degrade nitrate. The flow from the FB-reactor enters the first cell by gravity through a 0.25 inch diameter flexible PVC tube that feeds a PVC manifold submerged in the turf bed of cell one to disperse the LWE flow.
Following the fully vegetated cell is a VSB cell filled with turf pebbles, roughly 0.25-1-inch in diameter. The top 6 inches of the cell are sandy loam with fully vegetated wetland plants. The flow of LWE through the cell will remove most of the remaining BOD and TSS through biofilm activity and adsorption. LWE enters and exits the second cell through a 0.75 inch PVC tube located at the top of the shared wall with cells one and three.
The third cell (FWS) has open water, holding submerged water plants in a well-lit and aerated environment. The aerobic conditions with greater water clarity promote BOD reduction and sun radiation reduces pathogen count. The maximum HRT for the third cell is two days to prevent algae growth. Submerged pondweed (Potamogeton L.) and waterweed (Elodea Michx.) planted on the cell bed will increase aeration of the LWE and reduce TSS and nutrients levels. The CWT discharge is through a 0.75 inch flexible PVC tube at the base of the rear wall of cell three. By adjusting the height of the outflow tube end, the water level in the CWT canal and outflow rate can be regulated. Total system inflow and outflow will be recorded with a 0.75 inch analog water meter. To evaluate the efficiency of aerated-FBR-CWT, samples of LWE effluent will be analyzed prior and after treatment. The quality of fertilizer produced at the FB-reactor will be evaluated based on the struvite content in the fertilizer. Prior to this study, ICP- OES analysis will be used to quantify the ionic content of nutrients and pollutants. LWE samples will be taken twice a week at 8am and 4pm over a two-month period at each site, to account for fluctuations in CWT operation with thermal and fauna activity. Samples will be taken from LWE at entry to the aerated-FBR, entry to the CWT and outflow from the CWT, for a total of 192 samples. Each sample will be filtered to separate solids with 0.45 micron filter and acid digested prior to analysis. Treated samples will be analyzed in duplicate for COD, NH4-N, NO3-N using DR3900 spectrophotometer (Hach) analysis kits and in triplicate for OP, using ICP-OES (Agilent). TSS analysis of samples will be done by evaporating in a furnace at 105 deg-C. The pH and effluent temperature at the FB-reactor entry, and the CWT entry and outflow will be measured at the time of sampling.
Study on-site placement is set to begin on February 2018 at the dairy farm location. Placement at the swine farm is planned for August 2018.
Education & Outreach Activities and Participation Summary
The project placement will begin on February 2018
Project placement will begin on February 2018