Martin M. Karpiscak

Fate of organics during soil-aquifer treatment: sustainability of removals in the field.

A 5-year program of study was conducted at the Sweetwater Recharge Facilities (SRF) to assess the performance of surface spreading operations for organics attenuation during field-scale soil-aquifer treatment (SAT) of municipal wastewater. Studies were conducted utilizing both mature (approximately 10 yr old) and new infiltration basins. Removals of dissolved organic carbon (DOC) were robust, averaging >90 percent during percolation through the local 37-m vadose zone. The hydrophilic (most polar) fraction of DOC was preferentially removed during SAT; removals were attributed primarily to biodegradation. Reductions in trihalomethane formation potential (THMFP) averaged 91 percent across the vadose zone profile. The reactivity (specific THMFP) of post-SAT organic residuals with chlorine decreased slightly from pre-SAT levels (60 vs. 72 microg THM per mg DOC, respectively). Variations in the duration of wetting/drying periods did not significantly impact organic removal efficiencies.

Fate of indicator microorganisms, Giardia and Cryptosporidium in subsurface flow constructed wetlands

Limited information is available on the ability of subsurface flow wetlands to remove enteric pathogens. Two multi-species wetlands, one receiving secondary sewage effluent and the other potable (disinfected) groundwater were studied from February 1995 to August 1996, at the Pima County Constructed Ecosystems Research Facility in Tucson, Arizona. Each wetland had a retention time of approximately 4 days. The objectives of this study were (1) to evaluate the ability of multi-species subsurface wetlands to physically remove Giardia cysts; Cryptosporidium oocysts, total and fecal coliforms, and coliphages; and (2) to determine the likely impact of local wildlife on the occurrence of these indicators and pathogens. In the wetland receiving secondary sewage effluent, total coliforms were reduced by an average of 98.8% and fecal coliforms by 98.2%. Coliphage were reduced by an average of 95.2%. Both Giardia cysts and Cryptosporidium oocysts were reduced by an average of 87.8 and 64.2%, respectively. In the wetland receiving disinfected groundwater, an average of 1.3 x 10(2) total coliforms/100 mL and 22.3 fecal coliforms/100 mL were most likely contributed by both flora and fauna. No parasites or coliphages were detected.

REMOVAL OF PATHOGENIC AND INDICATOR MICROORGANISMS BY A CONSTRUCTED WETLAND RECEIVING UNTREATED DOMESTIC WASTEWATER

Wetlands containing floating, emergent and submergent aquatic plants, and other water-tolerant species have been found to economically provide a mechanism of enhancing the quality of domestic wastewater. The use of constructed wetlands for the removal of indicator bacteria (total and fecal coliforms), coliphages, protozoan parasites (Giardia and Cryptosporidium) and enteric viruses was investigated. A pilot scale constructed wetland consisting of two cells, one planted with bulrush and the other unplanted bare sand, were used to compare their efficiency in removing pathogens from raw sewage. Overall more than 90 percent of all microorganisms studied were removed by either of the two systems with a 1 to 2 day retention time. Removal of all mentioned microorganisms was greater from the surface flow in the unplanted cell than in the planted cell, except for Giardia and Cryptosporidium, although the differences were not statistically significant. Enteric viruses, coliphages and indicator bacteria were found to penetrate 2 m below the surface, although concentrations were reduced by greater than 99 percent in both cells. Less virus penetration into the sand occurred in the planted wetland versus the unplanted wetland. Water temperature was found to be the most important factor in the removal of enteric bacteria and viruses, while turbidity reduction was related to Giardia removal. These results demonstrate that significant reductions of pathogenic microorganisms can occur in constructed wetlands receiving untreated domestic wastewater with only a 1–2 day retention time.

CHEMICAL AND MICROBIAL CHARACTERIZATION OF HOUSEHOLD GRAYWATER

In arid areas, the search for efficient methods to conserve water is of paramount importance. One of the methods of water conservation available today is graywater recycling – the reuse of water from the sinks, showers, washing machine, and dishwasher in a home. The purpose of this project was to characterize the chemical and microbial quality of graywater from a single-family home with two adults. Water samples from a graywater holding tank were analyzed over a seven-month period for total coliforms, fecal coliforms, fecal streptococci, Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), and coliphages. The pH, turbidity, biological oxygen demand (BOD), suspended solids (SS), electrical conductivity (EC), sulfates (SO4), and chlorides (Cl) were also measured. The mean numbers of total coliforms, fecal coliforms, fecal streptococci, and P. aeruginosa were 8.03×107, 5.63×105, 2.38×102, and 1.99×104 CFU/100 mL, respectively. S. aureus and coliphages were not detected. In the chemical analysis, mean values of 7.47 for pH, 43 nephelometric turbidity units (NTU) for turbidity, 64.85 mg/L for BOD, 35.09 mg/L for SS, 0.43 mS/cm for EC, 59.59 mg/L for SO4, and 20.54 mg/L for Cl were measured. These data were compared to data taken in 1986 and 1987, when two adults and one child lived in the household. Analysis showed no statistically significant difference in levels of total coliforms and suspended solids between the two data sets. There were statistically significant differences in levels of fecal coliforms, pH, turbidity, chlorides, sulfates, and BOD between the two households. Fecal coliforms, turbidity, and BOD were higher in the household with two adults and one child. Levels of Cl, SO4, and pH were higher in the household with two adults.

Multi-species plant systems for wastewater quality improvements and habitat enhancement

The use of macrophytic plants for the treatment of municipal wastewater is growing rapidly. The Constructed Ecosystems Research Facility (CERF) is a joint project of the Pima County Wastewater Management Department and The University of Arizona9s Office of Arid Lands Studies. The facility consists of five 30-mil-hyperlon-lined raceways measuring 61 m long, 8.2 m wide, and 1.4 m deep and one slightly larger raceway. Research has been and is being conducted with aquatic plants such as water hyacinth ( Eichhornia crassipes ), duckweed ( Lemna spp.), giant reed ( Arundo donax ), bulrush ( Scirpus olneyi ), black willow ( Salix nigra ), and cottonwood ( Populus fremontii ). Composite water samplers are used to collect refrigerated samples from incoming secondary wastewater from Pima County9s Sewage Treatment Facility and from the effluent leaving each raceway. Water samples have been analyzed for parameters such as pH, BOD 5 , and total nitrogen. Microbiological studies have concentrated on the removal of indicator coliform bacteria, as well as Giardia , Cryptosporidium and viruses from the wastewater. Data from the water quality studies indicate that these constructed ecosystems reduce BOD 5 consistently to below the 10 mg/L BOD 5 tertiary standard, remove nitrogen as well as decrease the concentration of pathogens significantly.

Optimization of Artificial Wetland Design for Removal of Indicator Microorganisms and Pathogenic Protozoa

The enhancement of water quality by artificial wetland systems is increasingly being employed throughout the world. Three wetlands were studied in Tucson, AZ to evaluate their individual performance in the removal of indicator bacteria (coliforms), coliphage, and enteric pathogens (Giardia and Cryptosporidium). A duckweed-covered pond, a multi-species subsurface flow (SSF) and a multi-species surface flow (SF) wetland were studied. Removal of the larger microorganisms, Giardia and Cryptosporidium, was the greatest in the duckweed pond at 98 and 89 percent, respectively. The lowest removal occurred in the SF wetland, 73 percent for Giardia and 58 percent removal for Cryptosporidium. In contrast, the greatest removal of coliphage, total and fecal coliforms occurred in the SSF wetland, 95, 99, and 98 percent respectively, whereas the pond had the lowest removals (40, 62, and 61 percent, respectively). Sedimentation may be the primary removal mechanism within the duckweed pond since the removal was related to size, removal of the largest organisms being the greatest. However, the smaller microorganisms were removed more efficiently in the SSF wetland, which may be related to the large surface area available for adsorption and filtration. This study suggests that in order to achieve the highest treatment level of secondary unchlorinated wastewater, a combination of aquatic ponds and subsurface flow wetlands may be necessary.

Giardia and Cryptosporidium removal from waste‐water by a duckweed (Lemna gibba L.) covered pond

Aims: To determine the ability of duckweed ponds used to treat domestic waste‐water to remove Giardia and Cryptosporidium.

Management of Dairy Waste in the Sonoran Desert Using Constructed Wetland Technology

An integrated wastewater treatment facility, consisting of upper (solids separators, anaerobic lagoons, and aerobic ponds) and lower (wetland cells) subsystems, has been built to replace the lagoon at a dairy in Arizona, USA. The collection sump of the new waste treatment facility collects all dairy wastewater outflow. Wastewater is then pumped to solids separators, and flows by gravity to anaerobic ponds and aerobic ponds. The upper subsystem is expected to treat the water sufficiently so that the wetland cells may achieve further pollutant reductions. The lower subsystem, comprised of 8 surface wetland cells with an approximate surface area of 5,000 m 2 , receives outflow from the ponds. The cells are planted with cattail ( Typha domingensis ), soft-stem bulrush ( Scirpus validus ), and reed ( Phragmites australis ). After treatment is completed via the lagoons and ponds followed by the wetland cells, the wastewater can be reused to flush barns or to irrigate crops. Performance of the overall system is evaluated by measuring physical, chemical and biological parameters in water samples taken from selected locations along the treatment system. Chemical parameters studied include biochemical oxygen demand, pH, total suspended solids, nitrogen species. Biological monitoring included coliforms (total and fecal) and Listeria monocytogenes .

Transport of Coliphage PRD1 in a Surface Flow Constructed Wetland

A tracer study was conducted in a 3-ha surface flow constructed wetland to analyze transport performance of PRD1, an enteric virus model. The convection-dispersion equation (CDE), including a first-order reaction model, adequately simulated transport performance of PRD1 in the wetland under an average hydraulic loading rate of 82 mm/d. Convective velocity (v) and longitudinal dispersion coefficient (D) were estimated by modeling a conservative tracer (bromide) pulse through the wetland. Both PRD1 and bromide were simultaneously added to the entering secondary treated wastewater effluent. The mass of bromide and PRD1 recovered was 76 and 16%, respectively. The PRD1 decay rate was calculated to be 0.3/day. The findings of this study suggest that the CDE model and analytical moment equations represent a suitable option to characterize virus transport performance in surface flow constructed wetlands.

Microbial water quality improvement by small scale on-site subsurface wetland treatment

Abstract It has been demonstrated that large constructed wetlands used for domestic wastewater treatment are useful in the reduction of enteric microorganisms. This study evaluated the ability of three small-scale, on-site subsurface wetlands with different vegetation densities to remove total coliforms, fecal coliforms, coliphage, Giardia and Cryptosporidium. These wetlands were found to be equally efficient in the removal of enteric bacteria and coliphage as larger constructed wetlands. Giardia and Cryptosporidium were usually undetectable after passage of the wastewater through the subsurface wetlands. Coliphage removal increased with increasing vegetation density.