Sand Bioreactors Research Articles

Impact of salinity and time on structure and functional potential of wastewater treatment biofilms in intermittent sand bioreactors.

High salt wastewater is produced in industries, including seafood and pickling processing. The salinity in such wastewaters has been shown to negatively impact biological treatment efficacy. Little is known about the changes in the microbial community structure in the mature biological 2 treatment systems, the impacts of salinity on community composition, and the shifts over time during operation. This study aimed to identify the changes in the microbial community due to both salt and days of operation through 16s rRNA sequencing and KEGG functional predictions. Intermittent sand bioreactors (ISBs) with a focus on ammonia treatment were utilized. Results showed that the overall community structure and diversity were distinct as wastewater salinity varied from 0%-1.3%. At 1.3% salinity Zoogloea, a common genus in wastewater treatment plants, was not present and Aequorovita, Thauera and Dokdonella became the dominant genera. Nitrosomonas, an important ammonia oxidizing bacteria, increased in abundance with days of operation but was not significantly impacted by an increase in salinity. This finding was further supported by an increase in predicted nitrification potential with time of operation within all intermittent sand bioreactors tested. These results provide a deeper understanding of the impacts of salinity on microbial community development in biological treatment systems and elucidate the shifts in community structure occurring during early operations and into system maturity.

Impact of Salinity and Inoculation on Microbial Communities in Intermittent Sand Bioreactors

Impact of Salinity and Inoculation on Microbial Communities in Intermittent Sand Bioreactors

Treatment of seawater salinity sewage with intermittent sand bioreactors.

In water stressed areas, flush toilets using fresh water are unsustainable. This paper explores the ability of intermittent sand bioreactors (ISBs) to treat seawater salinity septic tank effluent for on-site wastewater treatment in coastal regions. Two ISB designs, sand only and layered sand and gravel, are compared for treatment efficacy. Six columns of each design were constructed in the laboratory and dosed four times per day, for a total hydraulic loading rate of 4 cm/day, with artificial seawater salinity septic tank effluent over 21 months. Average TOC and ammonia removal for both designs averaged >90% and >96%, respectively. No statistically significant difference existed in the percent removal or effluent concentrations between the two designs. Half of the columns of each design produced effluent with >4 mg/L ammonia at least once during the study, resulting in discontinuation of wastewater application for seven weeks. This resting approach resulted in effective treatment for up to 9 months (limited by the end of the study). The results indicate that both ISB designs can treat artificial seawater salinity septic tank effluent, but that an additional 1/3 capacity is needed to maintain a consistent hydraulic loading rate while accounting for resting ISBs when treatment efficacy declines.

Achieving drinking water compliance levels for metaldehyde with an acclimated sand bioreactor

Metaldehyde removal was delivered to below the 0.1 μg L−1 regulatory concentration in a laboratory scale continuous upflow fluidised sand bioreactor that had undergone acclimation through selective enrichment for metaldehyde degradation. This is the first reported case of successful continuous flow biological treatment of metaldehyde from real drinking water sources treating environmentally realistic metaldehyde concentrations. The impact of the acclimation process was impermanent, with the duration of effective treatment directly related to the elevated concentration of metaldehyde used during the enrichment process. The efficacy of the approach was demonstrated in continuous flow columns at both laboratory and pilot scale enabling degradation rates of between 0.1 and 0.2 mg L−1 h−1. Future work needs to focus on optimisation of the sand bioreactor and the acclimation process to ensure viability and feasibility of the approach at full scale.

Effect of Sodium Chloride Concentration on Removal of Chemical Oxygen Demand and Ammonia from Turkey Processing Wastewater in Sand Bioreactors

HighlightsSand bioreactors can effectively treat organic matter at salt levels at least up to 13 g L-1 NaCl.Acclimation of the systems for ammonia removal can take >4 weeks.Clogging and reduction in treatment efficacy can be alleviated through resting of sand bioreactors. Abstract. The treatment of high salt (>1%) wastewater is an issue in several food industries, including meat curing, vegetable pickling, and fish processing. Novel solutions involving biological treatment of saline wastewaters are increasingly important as companies strive to minimize waste production. Sand bioreactors are a secondary treatment option that do not produce secondary sludge. The purpose of this study was to assess the feasibility of treating high salt content poultry processing wastewater with sand bioreactors. Twelve laboratory-scale sand bioreactors consisted of 14.5-cm diameter columns with three layers composed of 15 cm of gravel, 15 cm of coarse sand, and 46 cm of fine sand. The columns were dose fed at 4 cm day-1 turkey processing wastewater with 0, 6, and 13 g L-1 NaCl. Removal of chemical oxygen demand (COD) and ammonia were monitored for over an 11-month period. Each bioreactor successfully removed >90% COD and ammonia during steady state after 4 to 5 week of acclimatization. Clogging caused a decrease in treatment in three sand bioreactors after 6 to 7 months, but was alleviated with rest periods. Keywords: Ammonia removal, Clogging, High salt wastewater, Organic matter removal, Sand bioreactor, Turkey processing wastewater.

Treatment of Meat-processing Wastewater with a Full-scale, Low-cost Sand/Gravel Bioreactor System

Abstract. A full-scale sand/gravel bioreactor system was constructed to treat turkey processing wastewater. The system was designed to treat 757,000 L day-1 at a surface application rate of 6 cm day-1. Twelve 25 × 55 m sand bioreactors cover 1.6 ha on the plant property site. Construction cost was $1,426,000 (2011-2012) and operating costs were $57,600 per year. Normalized to volume of wastewater treatment, the estimated (2013) capital and operation cost is $1.03 m-3. The plant began discharging effluent in 2013. Throughout 30 months, the plant has met all effluent requirements for CBOD5, TSS, and fat, oil, and grease (FOG). FOG was always below the detection level of 5 mg L-1 in the treated effluent. Ammonia is removed by the sand/gravel bioreactors through the summer months. During the winter/spring months, supplemental ammonia removal with an ion-exchange system is used to meet effluent standards. The low cost of the sand bioreactor system makes it suitable for small-scale meat processors. Keywords: Ammonia removal, FOG (fat, oil and grease), Sand filtration, Turkey processing, Ion-exchange.

Microbial Communities in Sand Bioreactors Treating High Salt Content Food Industry Wastewater

Microbial Communities in Sand Bioreactors Treating High Salt Content Food Industry Wastewater

Bacterial nitrogen fixation in sand bioreactors treating winery wastewater with a high carbon to nitrogen ratio

Heterotrophic bacteria proliferate in organic-rich environments and systems containing sufficient essential nutrients. Nitrogen, phosphorus and potassium are the nutrients required in the highest concentrations. The ratio of carbon to nitrogen is an important consideration for wastewater bioremediation because insufficient nitrogen may result in decreased treatment efficiency. It has been shown that during the treatment of effluent from the pulp and paper industry, bacterial nitrogen fixation can supplement the nitrogen requirements of suspended growth systems. This study was conducted using physicochemical analyses and culture-dependent and -independent techniques to ascertain whether nitrogen-fixing bacteria were selected in biological sand filters used to treat synthetic winery wastewater with a high carbon to nitrogen ratio (193:1). The systems performed well, with the influent COD of 1351 mg/L being reduced by 84–89%. It was shown that the nitrogen fixing bacterial population was influenced by the presence of synthetic winery effluent in the surface layers of the biological sand filters, but not in the deeper layers. It was hypothesised that this was due to the greater availability of atmospheric nitrogen at the surface. The numbers of culture-able nitrogen-fixing bacteria, including presumptive Azotobacter spp. exhibited 1–2 log increases at the surface. The results of this study confirm that nitrogen fixation is an important mechanism to be considered during treatment of high carbon to nitrogen wastewater. If biological treatment systems can be operated to stimulate this phenomenon, it may obviate the need for nitrogen addition.

Treatment of Turkey Processing Wastewater Using Sand and Textile Bioreactors

<abstract> <b><i>Abstract. </i></b> High strength wastewater can be effectively treated with sand bioreactors. Fats, oils, grease, and large, slowly degradable solids can clog the sand. The goal of this study was to compare sand bioreactor design by using either layers of coarse sand with pea gravel or layers of textile chips for wastewater pretreatment. Influent turkey processing wastewater varied from 840-3,920 mg COD L^-1 and 463-2,260 mg BOD₅ L^-1 was applied at 66 L m^-2 day^-1 (1.63 gal ft^-2 day^-1). The bioreactors reached >95% and >99% removal of COD and BOD₅, respectively, within one month of operation. Clogging tests were performed on sand/gravel and sand/textile bioreactors after 15 and 19 months of operation. Results indicated 30% to 40% filter clogging and this did not affect BOD₅ and COD removal negatively in the bioreactors. The bioreactors operated successfully for a total of 25.8 months before the experiment was terminated.

Using a Hydroponic System with Tall Fescue to Remove Nitrogen and Phosphorus from Renovated Turkey Processing Wastewater

Abstract. Rising nitrogen and phosphorus related nutrient pollution in different aquifers, as indicated by the deterioration of water quality, triggered this study. The aim of this study was to use commercially valuable ornamental plants, such as tall fescue, for wastewater treatment without decreasing the overall treatment efficiencies of a laboratory-scale hydroponic (soilless) system. Renovated turkey processing wastewater, from a sand bioreactor treatment system at a turkey processing plant, was used in this experiment. Nitrate and phosphate were measured in influent and effluent of the hydroponic system to evaluate the nutrient removal efficiency. Tall fescue was cultured on media consisting of perforated plastic plates and one layer of burlap. Water samples were tested at 12 h intervals under 2-day hydraulic retention times. Average removals of 53% nitrate and 68% soluble reactive phosphate were achieved at 48 h under 2-day hydraulic retention time. The 2-day retention time was optimal for nutrient removal at 22 to 28 days of growth. The plant nutrient content was also determined. The tall fescue hydroponic system, including possible microbial participation, accounted on average for 14% nitrate-N and 42% P removal. Improvement in the efficiencies could come from a better understanding of the biological mechanisms and controls of nutrient removal.

Analysis of substrate degradation, metabolite formation and microbial community responses in sand bioreactors treating winery wastewater: A comparative study

There is a global need for the implementation of more cost-effective green technologies for the treatment of effluent from wineries. However, systems reliant on microbial biodegradation may be adversely affected by the highly seasonal character of cellar waste. In this study, the biodegradation of two different formulations of winery effluent in sand bioreactors was compared. The degradation of organic substrates and formation of metabolites was monitored by physicochemical analyses of pore water and final effluent samples. Changes in the bacterial community structures were detected using molecular fingerprinting. In wastewater with an overall COD of 2027 mg/L, a formulation with a high concentration of acetate (800 mg COD/L) was more recalcitrant to degradation than a formulation with a high concentration of glucose (800 mg COD/L). Ethanol, glucose and phenolics were degraded preferentially in the deeper layers of the sand bioreactors (average Eh 25 mV) than in the superficial layers (average Eh 102 mV). The redox status also played a pivotal role on the bacterial community composition. The study yielded valuable insight that can be utilized in the design (configuration and operation) of full scale sand bioreactors.

A Potential Sanitary Sewer Overflow Treatment Technology: Fixed‐Media Bioreactors

Under certain conditions, sanitary sewer overflows (SSOs) containing raw wastewater may be discharged to public land and can contribute to environmental and public health issues. Although this problem has attracted the attention of local, state, and federal government and regulators, relatively little SSO abatement research has been published. This study used fixed-media bioreactors, a proven onsite technology in rural areas, to treat wet weather SSO wastewater and reduce its effects on the receiving water environment. The results of this 32-month laboratory study showed that fixed-media bioreactors, especially sand bioreactors, efficiently removed organic matter, solids, and nutrients during six-hour simulated SSO peak flows. Five-day biochemical oxygen demand (BODs) of the simulated SSO varied between 40 and 125 mg/L. The average effluent concentration of BOD5 was 13 mg/L in sand bioreactors at a hydraulic loading rate of 20.4 cm/h. In addition to having high hydraulic loadings, SSO events occur infrequently. This irregularity requires that treatment systems quickly start up and effectively treat wastewater after a period of no flow. This research found that an interval up to six months between two SSO peak flows did not affect the bioreactor performance. Based on this work, fixed-media bioreactors have the potential to reduce the effects of SSOs on the water environment by following proper design parameters and operation strategies. The pollution loading of approximately 18 g BODs/m2 x h is recommended for the efficient performance of sand bioreactors in the SSO treatment.

Attenuation of pollutants in sanitary sewer overflow: Comparative evaluation of treatment with fixed media bioreactors

Five types of fixed media bioreactors (biofilters) – sand, felt (textile), peat, felt/sand, and peat/sand – were used to treat sanitary sewer overflow (SSO). A simulated 6-h peak flow of a 25-yr SSO event contained 40–125 mg/l biochemical oxygen demand (BOD 5) and was loaded on the bioreactors at a high hydraulic loading rate of 0.2 m/h. The sand bioreactors were the most effective in the treatment, reducing BOD 5 by 84 ± 9%. The combination media peat/sand and felt/sand showed similar efficiency with peat, higher than felt. After the initial start-up, all the bioreactors reached >90% reduction of total suspended solids. The bioreactors also effectively removed ammonia and total phosphorus concentrations in a 2-h SSO loading, which would occur more often than a 6-h peak flow in a 25-yr SSO event. The effluent concentration of nutrients increased with continued loadings after the first 2 h.

Pretreatment of turkey fat-containing wastewater in coarse sand and gravel/coarse sand bioreactors

Fat, oil and grease in wastewater can be difficult to treat because of their slow decomposition. Traditional pretreatment facilities to remove fat, oil and grease from wastewater are increasingly costly. The hypothesis in this study was that pretreatment of animal fat-containing wastewater in sand and sand/gravel filters facilitates the conversion of slowly degradable organic matter measured as the difference between chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD 5) for subsequent biological treatment. The pretreatment was evaluated using simulated turkey-processing wastewater and coarse sand and sand/gravel filters at a constant hydraulic loading rate of 132 L/m 2/day. Two types of fixed media reactors were employed: (i) one set with a varying depth of coarse sand, and (ii) the second was similar but with an additional pea gravel cap. The results indicated that the relative removal of COD was slightly improved in the sand bioreactors with a pea gravel cap irrespective of the depth of coarse sand, but partial conversion to BOD 5 was not consistently demonstrated. Pea gravel may act as a sieve to entrap organic matter including fat globules from the wastewater. Multiple dosing at the same daily loading rate slightly improved the treatment efficiency of the sand bioreactors. The ratios of influent-COD/effluent-COD were always greater than 1.0 following a change in the dosing frequency after a rest period, suggesting that organic matter, specifically fat globules in this case, was retained by the column matrix.

Recovery of Sand Bioreactor Performance through Resting Following Treatment of Turkey Processing Wastewater

This research investigated the impact of resting on the performance of sand bioreactors treating turkey processing wastewater. Sand bioreactors received either raw turkey processing wastewater or a mixture of raw turkey processing wastewater and 0.04% of Ivory detergent. Two- and three-layer structured sand bioreactors were operated indoors at a hydraulic loading rate of 132 L/m2/day at 60 min dosing intervals. First sand bioreactor operation was terminated when excessive ponding occurred. After resting for 35 days at 264C, the second sand bioreactor operation was performed under similar operational conditions. Higher treatment efficiencies of TOC and BOD5 and greater total removed TOC and BOD5 were achieved following the 35 days of resting in the two- and three-layer sand bioreactor, and operation could be extended without clogging in the subsequent second runs. Thus rest periods could be used to recover treatment performance of sand bioreactors. Resting of drained sand bioreactors improved the treatment performance and lengthened the bioreactor runs. A rest period for 35 days was sufficient to recover the sand bioreactor performance. Reclamation of top layer of the sand bioreactor, such as plowing and raking, is recommended to improve the restoration effect because natural ventilation of the sand bioreactor is required during and after the rest period. Periodic operation of sand bioreactors would also be beneficial. Periodical turnover of the 1- or 2-in. top layer of pea gravel is recommended because it will improve aeration and disperse the accumulated fat.

Treatment of turkey processing wastewater with sand filtration

This research investigated the feasibility of coarse/fine sand filtration for removing organic materials from turkey processing wastewater. Sand filtration was tested with three organic and hydraulic loadings. Six two-layer sand bioreactors were in three groups, each with 5 cm layer of pea gravel at the bottom to support layers of fine sand (46 cm) and coarse sand (15 cm) to a height of 66 cm. The bioreactors were inoculated with a mixture of 20% (vol/vol) of wastewater lagoon sludge, 40% (vol/vol) of turkey processing wastewater, and 40% (vol/vol) of BOD 5 dilution water before starting the column operation with turkey processing wastewater. The wastewater contained 1270 ± 730 mg COD/L and was applied to each sand bioreactor at hydraulic loading rates of 264, 132 and 66 L/m 2/day. Each group comprised duplicate columns with the identical hydraulic loading. A commercially available detergent, Ivory TM, was added to the wastewater at 0.04% (wt/vol). Maximum treatment efficiencies were reached within a week. The removal of TOC and BOD 5 was >94% during 80 days of column operation at low and medium hydraulic loading rates (⩽132 L/m 2/day). The removal at the highest hydraulic loading rate (264 L/m 2/day) declined after the appearance of a black zone in the top layer of fine sand on day 30 for one reactor and day 50 for the other. The sand filtration in this study represents a feasible treatment for turkey processing wastewater and its efficiency and the life span of the process are associated with the extent of hydraulic loading of the sand bioreactors.

Enhancement of 2,4-dinitrotoluene biodegradation by Burkholderia sp. in sand bioreactors using bacterial hemoglobin technology.

Continuous flow sand column bioreactor experiments were conducted to investigate the effect of 2,4-dinitrotoluene (DNT) concentration (i.e. DNT loading rate) and influent dissolved oxygen (DO) concentration on aerobic biodegradation of DNT by wild type (DNT) and recombinant (YV1) Burkholderia sp., the latter containing plasmid pSC160 which carries the gene (vgb) encoding the hemoglobin (VHb) from the bacterium Vitreoscilla. The experiments were conducted in two continuous flow packed bed sand column bioreactors, one growing the wild type strain and the other growing YV1. Under oxygen-rich feed conditions (6.8 mg DO/L in the feed) with an influent DNT concentration of 99.6 mg/L (DNT loading rate approximately = 9.2 mg/m2/day), the effluent DNT concentration from the wild type bioreactor reached 0.7 mg DNT/L in 40 days whereas it was less than 0.2 mg DNT/L for the YV1 bioreactor in about 25 days. When influent DNT concentration was increased to 214 mg/L (DNT loading rate approximately = 20.3 mg/m2/day) while maintaining the same influent DO level of 6.8 mg/L, the effluent DNT concentration increased to about 5 mg/L for the wild type bioreactor whereas it was maintained at less than 0.2 mg/L for the YV1 bioreactor. Additionally, when influent DO was reduced from 6.8 mg/L to 3.1 mg/L while the influent DNT concentration remained at 214 mg/L, the effluent DNT concentration increased to more than 20 mg/L for the wild type bioreactor but up to only 1.7 mg/L for the YV1 bioreactor. A subsequent increase of influent DO back to 6.6 mg/L reduced the effluent DNT concentration to about 5 mg/L for the wild type bioreactor and to 0.10-0.19 mg/L for the YV1 bioreactor. These results confirm the utility of vgb technology to enhance biodegradation of aromatic compounds under hypoxic conditions and also that this enhancement can be maintained over extended periods of time as evidenced by plasmid stability in Burkholderia YV1.