Recent legislation in North America suggests stricter control will soon be put on the release of nitrogen and P-laden greenhouse wastewater into the environment ( OGVG, 2012 ). Unlike nitrogen, conventional treatment systems for greenhouse
C. Siobhan Dunets and Youbin Zheng
Christy T. Carter and Catharine M. Grieve
to provide irrigation water for agricultural crops ( Parsons, 2000 ). Many states have also begun using treated, reclaimed municipal wastewater as a source of irrigation water for agricultural crops to reduce the need for high quality water ( Carter
Ugur Bilgili, F. Olcay Topac-Sagban, Irfan Surer, Nejla Caliskan, Pervin Uzun, and Esvet Acikgoz
Wastewater sludge contains high levels of organic matter and significant amounts of essential nutrients and trace elements for plant growth. Moreover, sludge can be considered a slow-release fertilizer as a result of its high concentration of
J Austin Gimondo, Christopher J. Currey, Darren H. Jarboe, Martin Gross, and William R. Graves
oils; animal manures; fish emulsion; coproducts of wastewater treatment, like sludge and millorganite; and algae ( Chaney et al., 1980 ; Mulbry et al., 2005 ; Nelson et al., 2010 ; Schrader et al., 2013 ). Of these sources, algae, specifically that
Ricardo González-Ponce, Esther G. López-de-Sá, and César Plaza
great deal of interest in recent years ( de-Bashan and Bashan, 2004 ; Shu et al., 2006 ). Struvite (MgNH 4 PO 4 ·6H 2 O) is a potentially marketable product for the P fertilizer industry, which can be recovered at municipal wastewater treatment works
María José Gómez-Bellot, Pedro Antonio Nortes, María Fernanda Ortuño, María Jesús Sánchez-Blanco, Karoline Santos Gonçalves, and Sebastián Bañón
development ( Feigin et al., 1991 ). Alternative sources of water such as treated wastewater are therefore required to satisfy the needs of crops and its use is gradually becoming a common practice worldwide ( Angelakis et al., 1999 ). One of the advantages of
Christy T. Carter and Catherine M. Grieve
industry, especially greenhouse growers, has been to use lower quality water and/or greenhouse effluents to irrigate their crops. Many growers have also found applications for saline or degraded wastewaters in their own operations that continue to allow
Frederick S. Davies and Michael A. Maurer
Reclaimed municipal wastewater has been used to irrigate young and mature sweet orange and grapefruit trees in Florida. In the central ridge area of Florida, trees receiving reclaimed wastewater had greater yields and improved tree vigor compared to trees receiving wellwater. The high level of reclaimed wastewater applied (2.54 cm/week), however, decreased fruit total soluble solids, acids, and their ratio. In contrast, tree vigor and fruit quality were not different for mature grapefruit trees growing in the coastal, flatwoods area of Florida, which received reclaimed wastewater or canal water. Yields, however, were higher for the reclaimed wastewater treatments in one season, but the effect was variable. No adverse effects of applying high levels of reclaimed wastewater were noted at either site. The use of reclaimed wastewater for citrus irrigation has potential benefits for Florida citrus growers in the future.
Jennifer C. Bradley and J.M. Zajicek
A current trend in environmental practices concerns using constructed wetlands for wastewater treatment. The ecological values of wetlands have long been known. Wetland plants aid in the treatment of water pollutants by improving conditions for microorganisms and by acting as a filter to absorb trace metals. Wetlands now are being considered for industrial, municipal, and home wastewater treatment. Constructed wetlands are an economical and environmentally sound alternative for treating wastewater. These constructed “cells” are designed to function like natural wetlands. In constructed wetlands, water flow is distributed evenly among plants in a cell where physical, chemical, and biological reactions take place to reduce organic materials and pollutants. Increasing numbers of environmentally conscious homeowners are installing wetland wastewater treatment systems in their backyards with the aid of licensed engineers. This installation is occurring despite of the lack of educational materials to aid in site selection, selection of appropriate plant materials, and long-term maintenance. Traditional wetland plant species currently are being selected and planted in these sites, and the resulting effect is often an unsightly marsh appearance. With increasingly more homeowners opting for this alternative system, a strong need exists for educational materials directed at this audience. Therefore, educational resources that can provide information to the public regarding the benefits of wetland wastewater systems, while promoting aesthetically pleasing ornamental plant species is needed. A hands-on guide for installing constructed wetlands, a home page on the World Wide Web, and an instructional video currently are being developed at Texas A&M Univ. These technologies will be demonstrated and the values, needs, and opportunities available for the horticultural industry in the area of wetland construction will be discussed.
Catherine M. Grieve, James A. Poss, and John H. Draper
To explore the possibility that saline wastewaters may be used to grow high value floriculture crops, the effects of salinity were tested on Helianthus annuus (L.). Sunflower cultivars Sunbeam and Moonbright were grown in 30 greenhouse sand tanks and irrigated initially with nutrient solution. One week after planting, saline treatments were imposed with solutions differing in ion composition. Fifteen tanks were irrigated with waters typical of agricultural wastewaters present in the San Joaquin Valley (SJV) and 15 tanks were irrigated with water compositions similar to saline tailwaters found in the Imperial and Coachella valleys (ICV). Five treatments of each salinity type were used with electrical conductivities (EC) of 2.5, 5, 10, 15, and 20 dS·m–1. Length of the flowering stems was significantly reduced as salinity rose to 20 dS·m–1. Reduction was more pronounced when the plants were irrigated with the sodium-sulfate dominated waters of SJV composition. Flower diameter was reduced when the EC of SJV waters exceeded 15 dS·m–1, but was not affected by any treatment when ICV waters were used. Salt tolerance in sunflower appears to be associated with mechanism(s) that regulate transport of potentially injurious ions. Both Na+and Cl- were partitioned to the lowest portion of the stem, and effectively excluded from the remainder of the shoot. This study illustrates that saline waters with EC = 15 or 20 dS·m–1 may be used to produce ornamental sunflowers without significant loss of quality. Salt stress also provides an environmentally friendly alternative to the use of growth regulators for the control of plant height.