ASTEWATER treatment a t Walt Disney World in Orlando, w Florida is accomplished in a 15-

mgd facility operated by Reedy Creek Energy Services (RCES). Commissioned in 1993, the treat- ment facility consists of four identi- cal process trains. Preceded by eight primary clarifiers, each process train is a series of cascading, continuously stirred tank reac- tors. Eight sec- rhe aerated ondary clarifiers, static pile deep bed filtration, facility and disinfection fin- generates ish the treatment compost from process. Gravity biosolidsr belts and belt filter ~';b:!::~~~ presses are used for trimmings for solids processing use at ,,isney prior to composting. world, About 50 wet tons of biosolids are produced per day.

Biosolids originally were land- filled. Soon thereafter, RCES built an aerated static pile facility to com- post the biosolids with wood chips and landscape trimmings. The piles were subjected to negative aeration with exhaust air directed to a biofil- ter. Food residuals and animal ma- nure were eventually added to the compost mix, the piles were posi- tively aerated, and the biofilter was eliminated.

For the next several years, RCES expanded the composting site to cap- ture all of the biosolids produced at the- wastewater treatment facility, and experimented with mixes and processes. Compost remained on- site until needed by a broker, who in turn resold the product to orange growers. In-house research deter- mined that the compost was inade- quately cured and contained exces- sive organic acids and soluble salts phytotoxic to annual plants. As a re- sult of this phytotoxicity, and tempo- ral inconsistency in compost quality, Walt Disney World Horticulture was unwilling to use RCES compost. In- stead, the horticulture division elect- ed to purchase compost from an out- side vendor for use as a soil amendment in annual plant beds.

Odor emanating from the com- posting facility in 1998 forced the suspension of operations. Biosolids and food-residuals-were-directektr landfills for disposal. A committee formed to address the issue deter- -

the most cost-effective option for biosolids stabilization and manage- ment. In addition, the committee wished to develop a maturation pro- cess that would produce compost ac- ceptable for horticultural use in the park's annual beds and on turf grass. Walt Disney World Horticul-

Biosolids Compost Utilization At Disney World Composting restarted at Disney World fL> 1%

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in 1999 and improved product quality cw t% +-& 3 -%i has led to use of the compost by the bAk.* .. 6f 6kv %

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ture could then use a11 of the com- post produced, negating RCES's need to store product until request- ed by the broker.

New Composting Approach Composting operations - han-

chips -were reestablished in 1999. Historically, the wood chips were purchased from an outside vendor. Presently, grinding pruned tree limbs and palettes, in combination with chip recovery, produces an ad- equate volume of wood chips for the mix. Food residuals, the cause of

previous odor problems, continued to be directed to a landfill. Stabiliza- tion is accomplished using a nega- tively aerated static pile and biofil- t e m d - t akesah t ; -28 -dags rTI r r mix then is formed into windrows for maturation and the piles are turnea'

turner. Target oxygen and tempera- ture ranges for the maturation windrows are five to 15 percent (ide- ally eight to 12 percent) and 35" to 60°C respectively. The combination of negatively aerated static piles, a biofilter, and mechanically-aerated maturation windrows was immedi-

ately effective in minimizing odors. ture used a t Walt Disney World and Remaining to be determined was consists of 50 percent peat moss, ten

how effective the process was for pro- percent green pine bark and 40 per- ducing a horticulture-grade end cent sand with an average pH of 6.5. product. The composting facility is Experimental treatments - - were con- capable of producing 15 tonslday of com- post, all of which could be used by Walt Dis- ney World Horticul- ture. Bioassays were identified as the best aaaroach for deter- &;ing if the revised treatment was replicated process was success- ten times. The study was fully producing high repeated for four differ- quality compost, and ent age RCES composts for determining the - zero, 28, 56 and 84 necessary length of days after stabilization. the maturation pro-

structed by applying one inch of compost to the top of each pot and mixing with a hand rake. This approach was intended to mimic application of compost to existing an- nual plant beds. Each

cess. Hence, bioassays were estab- lished for both annual plants and turf grass.

As part of a series of tests to evaluate compost quality, potted petunias were grown in an assortment of soil mixtures.

Annual Plant Bioassay Potted petunias (Petunia hybri-

da) were used to conduct the annu- al plant bioassays. Treatments in- cluded a potting soil control, potting soil mixed with vendor compost (in- vessel, biosolids-based), and potting soil mixed with RCES compost. The potting soil is analogous to the typ- ical annual bedding plantlsoil mix-

Individual survival, condition, color (Munsell color chart), size (height by width) and number of blossoms were monitored at the beginning of the experiment and every two weeks thereafter for 12 weeks. In addition, we assessed compost odor before and after mixing with the potting soil.

Plant survival was good through- out the study. Only three plants, one from each treatment, died. In addi- tion, the condition of the petunias was generally good to excellent and was comparable across treatments. Both the RCES compost and the vendor compost produced larger plants and more blossoms than the potting soil. RCES compost matured 56 days produced the greatest num- ber of blossoms. Plants grown in RCES compost aged 84 days were noticeably greener during the first two weeks, but not thereafter. Nei- ther the potting soil or the vendor's compost produced noticeable offen- sive odors. By itself, the RCES com- post had a noticeable and offensive odor if matured zero, 28 or 56 days, but not 84 days. The odor was not noticeable when mixed with potting soil when the compost was matured for 56 or 84 days.

Turf Grass Bioassay Preliminary studies indicated

that RCES compost was not harmful to turf grass. Bioassays were estab- lished to determine if the applica- tion rate had an effect on response, and if the odor was a prohibitive fac- tor. Three treatments were estab- lished on irrigated and nonirrigated

ktiJ Bahia grass (Paspalum notatum) - a control, 3 kglm2 of turf and 6 kg/m2

4 * "y of turf - five replicates per treat- $ ? ment. The experiment was repeated

for compost matured zero, 28, 56 and 84 days after stabilization. Gen- eral condition was monitored at the beginning of the experiment and ev- ery two weeks thereafter for 12 weeks. In addition, we assessed compost odor before and after appli- cation to the turf, and during each monitoring event.

Turf condition was largely indis- tinguishable among treatments for the nonirrigated plots, perhaps in

ticeable for compost matured zero, Turf treatment experiments were 28 and 56 days before and after ap- conducted wifh compost matured plication. The odor persisted for zero, 28, $6 and 84 days after

stabilization.

I about one week after application. No offensive odor was detected be- fore or after application for compost matured 84 days.

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Conclusions RCES has significantly reduced

biosolids disposal costs by develop- ing an effective in-house composting operation. All of the biosolids pro- duced a t the wastewater treatment facility now can be transferred to the composting facility for stabilization and maturation. Moreover, the oper- ation produces horticulture-grade compost. The compost is appropriate for use in planting beds when ma- tured for 56 days, and for application to turf when matured for 84 days. Production of horticulture-grade compost provides RCES with a reli- able end user in Walt Disney World Horticulture. Alternativelv. RCES is now positioned to sell its broduct a t a price greater than i t previously sold immature compost to the broker if production exceeds what the horti- culture division needs.

Walt Disney World Horticulture benefits from RCES's compost oper- ation by accessing compost of equal os better value than it previously ob- tained from outside vendors at a low- er cost. Eventually, the compost will be used as a peat substitute when annual plant beds are replaced. Hor- ticulture may achieve additional cost reductions if compost used in plant- ing beds reduces soil replacement rates, watering requirements and fertilizer application.

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Donald Kent is the principal of Envi- ronmental Idea ~ a n k , I&., Annette P n w l l ~ h r a , H-J n.re Il~zrh . - - Azurea, Inc., Jerry Hubbard is with Reedy Creek Energy Services and Pe- ter ~ a l o ~ r i d i s is-with Walt Disney World Horticulture. For more infor- mation please contact Don Kent a t dmkent@environmentalideabank.co m or Jerry Hubbard a t jerry.hub- bard@disney.com.