Research Project Summary Information
Water Treatment Residuals for Greenhouse Production:Water Treatment Residuals for Greenhouse Prod.(ST6596-1)
Upper Mohawk Valley
The Upper Mohawk Valley Regional Water Board (UMVRWB) produces about 700 cubic yards or about 600 wet tons of residual alum sludge per year from its water-treatment processes. The Water Board has stockpiled this material over the past 10 years, but is scheduled to begin disposal at a cost of $65 per ton, if a beneficial use for the sludge cannot be found. While the material has no nutrient value, it has potential as a potting soil ingredient to prevent clumping of soil used for bedding plants, similar to Styrofoam beads or perlite. A set of controlled plant growth trials were designed to assess the effect of alum addition to potting soil on plant growth parameters for a variety of plants. A Utica-area greenhouse, which uses about 50 cubic yards of soil and bedding media per day, provided assistance in conducting the growth trials, and is willing use alum sludge, if growth trials show the sludge to be a viable substitute for styrofoam or perlite.
Four greenhouse plants were assessed in controlled growth trials, including begonia, marigold, impatiens and chrysanthemums. Each trial consisted of a control (conventional potting mix) and four blends of alum sludge of 2%, 6%, 10% and 14% by volume for the first three plant types, and 4%, 8%, 12% and 16% by volume for the chrysanthemums. After a six-week growing period, with watering and fertilizer addition constant across controls and blends, parameters of plant growth were measured, including plant and root wet and dry mass; leaf area; plant height; number of leaves; and number of flowers per plant (except for chrysanthemums). Twenty individual plants were grown per control and blend condition, and five plants were sampled for testing in each trial. Chlorophyll content was analyzed in a subset of the plants sampled.
The UMVRWB plans to apply to the New York State Department of Environmental Conservation for a beneficial use determination that would permit transfer or sale of the slum sludge greenhouse growers as a potting soil ingredient. If approved, the designation would reduce the cost and energy required for disposal. UMVRWB would avoid paying $250,000 to $390,000 in fees for disposal, based on a beneficial use determination.
Plants had different tolerance to added alum sludge. Alum produced negative effects in begonia, in plant wet weight of 10%, while impatiens and marigold were affected at the 2% volume blend. Alum did not reduce root mass for begonia, while impatiens and marigold were affected adversely at the 10% volume blend. With respect to the effect of alum on leaf area, plant height, number of leaves and flowers for these plants types, marigold was the least tolerant, being adversely affected at a 2% volume blend, while begonia tolerated alum volume blends of 10% with impatiens in between. Chrysanthemums were found even more tolerant than begonia, as alum produced no effect on plant height and leaf area up to a 16% volume blend, although root mass was first adversely affected at a 12% alum blend. These results suggest that alum blends of less than 2% are likely to have no adverse affect on plant growth and can be used as a substitute for inert ingredients such as perlite or Styrofoam. If a beneficial use determination is granted to the UMVRWB, contact will be made with other water-treatment plants on the use of alum sludge in greenhouse plant production.
Upper Mohawk Valley
Regional Water Board 1 Kennedy Plaza
Utica, NY 13502
Waste Management and Pollution Prevention
Water/Wastewater treatment systems
NYSERDA Contact Information
R&D -Transport & Power Systems