Survey of Reclaimed and Non-reclaimed Irrigation Water Use for Production of Container-grown Plants in Florida

Significance to the Horticulture Industry

Reclaimed and non-reclaimed water users in Florida were surveyed to gain a better understanding about the potential use of this alternative water resource by non-users. Reclaimed water can be used without restriction during drought even though other sources of water, such as that from wells, are restricted sometimes in Florida. Active users infrequently observed plant disease attributable to reclaimed water and were satisfied with the quality and quantity of the reclaimed water. Seventy-one percent of non-reclaimed users agreed that expense of connection to a reclaimed system was a limitation. Additional results further support the premise that if nurseries were guaranteed a consistent supply of high quality reclaimed water and education was provided regarding the safety of reclaimed water and safeguards needed, this might enhance its use. Bruvold (1985) previously noted that education was important to adoption.

Introduction

The use of reclaimed municipal water as an irrigation source for nursery crops is increasing in importance, because of an increasing population. Population growth results in an increased demand for water, a limited resource, as well as increased production of sewage water to reclaim. The use of reclaimed water, processed sewage, is continuously being investigated to determine its viability as a replacement for potable water used for irrigation. In Florida, the processing of sewage is regulated by state statute. Processing facilities are permitted to produce reclaimed water of different qualities and hence, suitable for different applications or uses. For example, reclaimed water that was processed according to Part 111 of Florida Administrative Code 62-610 (Anonymous 2012) had a high level of disinfection (chlorination) and can be applied to public areas; whereas, this is not so for reclaimed water that was processed according to Part 11 of the Code.

Nurseries must have access to high quality water for optimal plant production, so all the nurseries that were active users of reclaimed water in the following investigation were using reclaimed water processed according to Part 111. The use of reclaimed water may help the nursery industry cope with limited supplies of potable water, as well as provide a use for reclaimed water that might otherwise be discharged to the environment.

Several studies have evaluated municipal wastewater or reclaimed water for irrigation of food crops (Neilsen et al. 1989a, Neilsen et al. 1989b, Neilsen et al. 1989c, Omran et al. 1988, Parsons et al. 1995, Parsons et al. 2001, Reboll et. al. 2000, Zekri and Koo 1994) and ornamental plants in production (Gori et al. 2000, Gori et al. 2004, Yeager et al. 2010) or in the landscape (Devitt et al. 2003, Parnell and Robinson 1990, Robinson and Parnell 1989).

Surveys regarding the use of reclaimed water have primarily focused on public rather than user opinion. Surveys of the public generally revealed a more favorable response to reclaimed water as human contact decreased (Bruvold 1988). In a study focused on users, Devitt et al. (2004) investigated the attitudes and perceptions of golf course personnel in the southwestern U.S. Thirty-six percent of the participants (89) used reuse (reclaimed) water. The primary reasons for using reclaimed water were mandates (33%), financial incentives (26%), belief that reclaimed water would be a more reliable water source (24%), and water conservation (15%). Participants using reclaimed water indicated irrigation scheduling (78%) was most often changed while drainage, soil preparation, fertilizers, soil amendments, and irrigation maintenance were changed by 65%. Of the 44% of participants that had classes regarding the use of reclaimed water, 89% indicated they were ‘better or somewhat better prepared to use reuse water for irrigation.’

The objectives of our survey were to determine production practices of container plant growers in Florida using reclaimed and non-reclaimed water in the same locale. Reclaimed water is not subject to the same drought restrictions as well water in Florida and these results could be used to promote the use of reclaimed water as an alternative to the well water that is used predominately in the container nursery industry.

Materials and Methods

The research study was designed using a descriptive survey instrument directly administered to purposive sampling of container nurseries that did and did not use reclaimed water. A list of container nurseries that used reclaimed water was not readily available, so the information was compiled by the authors. A list of reclaimed water treatment facilities for reuse type Public Access Areas & Landscape Irrigation (PAA&LI) and reuse subtype Other Public Access Areas (OPAA) for Part III reuse water was obtained from the Florida Department of Environmental Protection (FDEP) website Appendix D (Anonymous 2005), as suggested by Lauren Walker-Coleman, Reuse Specialist from FDEP (personal communication). She also provided a list of contact phone numbers for the reclaimed water treatment facilities in the state. From those lists, approximately 95 treatment facilities were contacted by phone and queried to determine if they supplied reclaimed water to wholesale nurseries producing plants in containers. If so, the nursery name was obtained. This resulted in a list of 22 users of reclaimed water statewide. Each nursery was then contacted to verify they sold plants wholesale and used reclaimed water for irrigation. If these conditions were met, an appointment was established for a visit to complete the survey. Some of the 22 users were out of business, grew plants in native soil, or no longer used reclaimed water. Seven nurseries were viable reclaimed water user candidates to participate in the survey.

A nursery not using reclaimed water in close proximity to a nursery using reclaimed water was also surveyed. Average distance between nurseries was 10 km (6.2 miles) for six of the users and non-users, and 59.5 km (37 miles) for the remaining user and non-user nurseries. Reclaimed water users were located in the counties of Brevard, Manatee, Orange, Pinellas, and Seminole; and non-users were located in the counties of Brevard, Manatee, Orange, Osceola, and Pinellas. Survey forms for users and non-users were approved by the University of Florida Institutional Review Board and personnel from each nursery signed a consent form.

All site visits were conducted between June 15, 2005, and January 12, 2006. Surveys were completed by participants during site visits except when participants wanted to complete and return the survey at a later time due to constraints with their schedule. The survey administered to users consisted of a series of questions addressing nursery demographics, questions that used a five-point Likert (1932) scale to evaluate attitudes and perceptions about reclaimed water use, free response questions that focused on past experiences using reclaimed water, and additional opportunities for comment. Average responses are reported where appropriate and ratings summarized. A rating of 1 or 2 indicated agreements, frequently observed, or satisfied and 4 or 5 indicated the opposite. A rating of 3 was considered neutral. The five-point Likert scale was also used for questions asked of non-reclaimed users. Surveys for non-reclaimed users contained questions addressing nursery demographics, and attitudes and perceptions regarding use of reclaimed water for irrigation of container plants.

A sample of the reclaimed water was obtained at each nursery. Elemental concentrations of reclaimed water (mg·L⁻¹) were determined for Al, Ba, B, Ca, Cd, Cl, Cu, Fe, K, Mg, Mn, Mo, Na, NH₄-N, Ni, NO₃-N, P, Pb, Si, and Zn in addition to pH and electrical conductivity (EC) using standard procedures (Anonymous 2011). Averages and standard deviations for the seven samples were determined.

Results and Discussion

The nurseries surveyed that used reclaimed water had been in business an average of 36 years (29 to 45, n = 7) and had used reclaimed water an average of 8 years (2 to 15 years, n = 7). Distance between water treatment facilities and nurseries averaged 1 km (0.6 miles, n = 6). Nurseries not using reclaimed water for irrigation of container plants had been in business an average of 32 years (27 to 45 years, n = 7).

Participants were questioned regarding their source of water for irrigation. For reclaimed water users, wells were reported by one of four respondents, municipal or potable water by one of five, and surface water was not a source of water for irrigation (Table 1). Even though wells and municipal potable water were available, reclaimed water comprised 95 to 100% of container plant irrigation (n = 7) for respondents that used reclaimed water (Table 1).

Table 1. Survey results for water sources used by nurseries that irrigated container-grown plants with reclaimed or non-reclaimed water.

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Well water was the source of irrigation water for five of six non-reclaimed users and well water comprised 65 to 100% of the total water applied from all sources according to respondents (Table 1). Surface water was the second most used source of water for non-reclaimed users followed by municipal or potable water.

Four of seven respondents using reclaimed water had a contract with their reclaimed water supplier. Maximum amount of reclaimed water received was 379 kL (100,000 gal) per day (n = 2). Four of seven respondents purchased reclaimed water and four of seven received a water analysis report from the supplier. Two of six respondents reported conducting their own nutrient analyses or hired someone.

For non-reclaimed users, the pH and alkalinity of irrigation water were monitored by three and two of seven respondents, respectively; however, electrical conductivity was not monitored. Two of seven respondents reported the collection and reuse of irrigation water with an estimated 45% of the water applied was collected for reuse. One of seven reclaimed water users reported the collection of irrigation water for reuse.

Consistent quality of reclaimed water is important if nursery personnel are going to embrace widespread use of this resource. Four of six responded 1 or 2, indicating that reclaimed water quality was consistent over time, one of six was neutral (responded 3), and one of six responded 4 or 5, noting inconsistent quality.

In a separate study, we evaluated the quality of reclaimed water processed to Part III standards by the Gainesville Regional Utilities Kanapaha Water Reclamation Facility in Gainesville, Florida. We collected three replicate samples approximately every 12 days and determined that NO₃-N and total P concentrations ranged from 1.6 to 4.6 and 0.5 to 2.9 mg·L⁻¹, respectively, during August 2005 to January 2006 (data not shown). Those concentrations were similar to concentrations for the samples collected from the nurseries surveyed that used reclaimed water (Table 2).

Table 2. Average values (± standard deviation) for nutrient analyses of reclaimed water from nurseries participating in the survey (n = 7). All values are mg·L⁻¹ (ppm) except for pH.

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The reclaimed water samples collected from nurseries surveyed (Table 2) had Cl concentrations and pH values in excess of desired levels for irrigation water (> 100 mg·L⁻¹ and < 7, respectively, Yeager et al. 2007). The high Cl may be a consequence of the disinfection process. Calcium concentrations in the reclaimed water exceeded the 20 to 40 mg·L⁻¹ (20 to 40 ppm) desirable range for a container substrate, while K was within the desirable (10 to 20 mg·L⁻¹) range (Yeager et al. 2007). Reclaimed water electrical conductivity averaged 0.96 ± 0.41 dS·m⁻¹; however, a noteworthy concern is that P in reclaimed water will contribute to P in watersheds that discharge to the Everglades. The Everglades Protection Area is targeted for 10 μg·L⁻¹ total P (Anonymous 2004) so it is advisable that producers of container plants in watersheds that discharge to the Everglades check with FDEP prior to using reclaimed water.

Survey questions about water quality were followed by questions addressing issues associated with reclaimed water application. One of the questions asked respondents to indicate whether 16 short statements applied to their use of reclaimed water. The need for filtration and very high pressure were noted by three of seven respondents; while two of seven indicated they had experienced fluctuating pressure, emitter or nozzle clogging, or health or safety concerns (data not shown). Need for acidification, pipes or valves breaking, lack of reliable supply, irrigation down time, loss of plant sales, disgruntled employees, and water treatment because of emitter or nozzle clogging were each noted by one of seven respondents. No one reported they were forced to take more water than needed, increased pesticide use, toxic reactions with fertilizers or chemicals, or water treatment necessary because of pathogens. Five of six respondents reported infrequent observation of disease, while all six respondents reported infrequent observations of non-disease related plant damage or unusual growth. Two of seven respondents had frequently observed enhanced plant growth or developmental differences attributed to the use of reclaimed water for irrigation, two of seven were neutral, and three of seven noted infrequent observation of enhanced plant growth or developmental differences. There was no report of physical or chemical treatment of reclaimed water prior to application even though in another question three of seven respondents recognized a need for filtration.

Additional questions about reclaimed water addressed the availability of water and the amount applied. Three of six responded 1 or 2 indicating that reclaimed water quantity was consistent with time, two of six were neutral (responded 3), and one of six responded 4 or 5 noting inconsistent quantity.

Reclaimed water was applied with overhead sprinklers outdoors or under shade on an average of 3.5 ha (8.6 A) [0.8 to 9.3 ha, 2 to 23 A (n = 6)]. The average amount of reclaimed water applied per day was 255 kL (67,300 gal) [76 to 454 kL, 20,000 to 120,000 gal (n = 3)] during peak demand. Similarly, for five non-reclaimed users, irrigation was applied with overhead sprinklers outdoors or under shade on an average of 4 ha (10 A) [0.8 to 9.3 ha, 2 to 23 A]. The average amount of water applied per day by non-reclaimed users was 227 kL (59,900 gal) [1.9 to 617 kL, 500 to 162,900 gal (n = 5)] during peak demand.

In greenhouses, two non-reclaimed users applied an average of 69.3 kL (18,300 gal) [37.9 to 100 kL, 10,000 to 26,500 gal] per day with overhead sprinklers during peak demand. The average area irrigated by non-reclaimed users with overhead sprinklers was 10,284 m² (110,700 ft²) [111 to 32,888 m², 1,200 to 354,000 ft² (n = 5)]. Five respondents reported using reclaimed water with overhead sprinkler irrigation in greenhouses on a slightly larger average area of 10,777 m² (116,000 ft²) [1486 to 24,155 m², 16,000 to 260,000 ft²]. Users and non-reclaimed users that applied irrigation in greenhouses, outdoors, or under shade provided insufficient information or no information about microirrigation, flood, ebb and flow, or other types of irrigation.

Categories of plants irrigated with reclaimed and non-reclaimed water are given in Table 3. All respondents reported growing woody shrubs in containers. Non-reclaimed users also reported growing ball-and-burlap trees and palms, palm tree liners, and retail nursery plants.

Table 3. Number of respondents that reported using reclaimed or non-reclaimed water irrigation for plants in each category.

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Controlled-release fertilizers typically used for container plant production supply nutrients for an extended period of time. Because irrigation water quality and quantity can impact the nutrient release, respondents were asked about the fertilizers used in conjunction with reclaimed water irrigation.

Controlled-release fertilizer was used by all seven reclaimed water users and five of seven non-reclaimed users (Table 4). Granular fertilizer applied in combination with controlled-release fertilizer and granular soluble fertilizers were the second most used. Five of seven reclaimed users and four of seven non-reclaimed users each used those fertilizers. Solution and natural organic fertilizers were each used by three of six non-reclaimed users and two of five reclaimed water users. Controlled-released fertilizer supplemented with solution fertilizer was used by two of six reclaimed water users and one of six non-reclaimed users. These data indicate that fertilizer use was similar for users and non-reclaimed users. Similar fertilizer use regardless of water source could be indicative of the fact that only two of seven respondents reported that it was necessary to change their fertilizer program because of reclaimed water. They reported decreased N in fertilizer and elimination of B from the micronutrients they applied. However, it is important to note that changes in fertilizer composition due to reclaimed water might be crop specific.

Table 4. Number of respondents that applied different types of fertilizers and irrigated container-grown plants with reclaimed or non-reclaimed water.

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Reclaimed water users were asked to rate their level of satisfaction regarding their experiences using reclaimed water. All seven users reported they were satisfied with their overall experience of using reclaimed water for irrigation and were satisfied with both the quantity and quality of reclaimed water (data not shown). Five of seven respondents reported they had received incentives to use reclaimed water. Incentives included lower production costs, more water, enhanced water quality, and incentive associated with water consumption permit renewal; although, that association was not given. Monetary incentives were most frequently reported.

Just as monetary incentives were important for active users, incentives could be important for non-reclaimed users to overcome the expense of connection and unknown water quality. The small average and standard deviation for expense of connection and unknown water quality indicate their importance when considering reclaimed water use (Table 5). It should be noted that water quality analyses conducted by the supplier of Part III reclaimed water are usually available if requested. However, additional infrastructure might be needed to rectify water quality issues as well as facilitate connection to the reclaimed water supply. Also, monetary incentives could help with limitations such as the need for water treatment and need for plumbing or retrofitting (Table 5) that could require additional infrastructure or additional costs.

Table 5. Number of non-reclaimed water users who expressed agreement or disagreement with reclaimed water limitations for container plant irrigation.

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Other limitations regarding reclaimed water use are given in Table 5. Health and safety concerns were noted by four of seven non-reclaimed users. Restrictions on existing water and expense of water were limitations for three of seven non-reclaimed users; while reliability of supply, forced to take water not needed, and regulations were limitations for two of seven non-reclaimed users. One of seven non-reclaimed users agreed that limited research on reclaimed water was a limitation. However, limited research and regulations were considered less of a limitation than expense of connection. When asked about other limitations on the use of reclaimed water for container plant irrigation or why respondents were not using reclaimed water, the responses generally focused on lack of availability.

The users of reclaimed water responded to questions about non-reclaimed water irrigation practices in their nurseries. There was insufficient number of responses for those questions so that information is not presented.

In summary, reclaimed water users were satisfied with quality and quantity of water used. Users did not report plant damage or unusual growth due to reclaimed water. Nurseries not using reclaimed water, but within 4.8 to 59.5 km (3 to 37 miles) of nurseries using reclaimed water, indicated they would use reclaimed water outdoors and under shade (six of seven respondents) or in greenhouses (four of five respondents) if available. Additionally, some of the limitations expressed by non-reclaimed users, such as unknown water quality, might be negated by education based on results from reclaimed water users.