Iwa international Specialist Conference

Abstract

There are several options for managing sludge. The different means of treating, using and disposing sludge have different financial costs; they also have different environmental costs. Ultimately they all depend on being accepted (or preferably welcomed) by “society”. Society no longer accepts having the best technical solution imposed upon them. In this context “society” includes everybody from the people in the vicinity of the facility/chimney/application site to food companies and environmental NGOs.
Sometimes dissatisfaction or unease results from sludge managers’ disregard of the reasonably needs of others (such as odour and traffic) but at others it is because of lack of understanding between the parties. Only dialogue, provision of information and development of mutual trust can bridge this lack of understanding.
This paper will discuss concepts of sustainable sludge management, including energy and natural resources; some of the examples will be co-processing centres for several streams of organic resources. From the technological side it will recommend that holistic solutions be adopted. It will also include examples of initiatives to build partnerships for sustainable organic resources. Several industries have found that there are benefits to “opening the factory gates” and sharing with their communities rather than keeping the gates closed and acting as if they are not part of the wider community. More than 140 stakeholders in the “plough to plate” chain agreed that sharing information and building mutual trust and consensus on good practice is the route to achieving this for organic resources (sludge, compost, manure). The paper will describe progress and a vision for the future.
25.

BIOSOLIDS APPLICATION TO SALINE-SODIC SOILS: ACID AND ALKALINE APPROACHES.

Barrios J. A., Jiménez, B., Garciapina T. and Murillo R. M.
Soil degradation worldwide was projected to produce a loss of 10 million hectares annually for the year 2000, being salinisation one of the major causes of soil degradation. Several organizations encourage the implementation of urgent measures to reduce soil degradation and ensure food production for the forthcoming generations. Salinity, together with sodicity are factors that severely limit the agricultural potential of soils. In some circumstances, their origin is anthropogenic while in others they are produced by naturally occurring processes. For example, irrigation for agricultural purposes has increased productivity of arid and semi-arid soils in several regions of the world. However, under certain conditions it has also increased soil salinity and sodicity due to an excessive application of water, poor drainage, and evaporation. On the other hand, there are cases where the natural configuration of the land produces closed basins that are flooded with surface runoff and rainfall. This situation gradually produces the deposition of sediments in the bed of the lake, thus reducing infiltration and increasing the salinity of the lake due to evaporation. With regards to sodium, it may be caused by several factors, like a shallow groundwater table, which reduces drainage and produces an accumulation of sodium in the root zone.
Mexico is considered a semi-arid country in two thirds of its area and presents both scenarios. Salinity and sodicity are present especially in the Northern and Northwestern regions but also in well localised areas. For example, the Valley of Juarez, located in the Mexican State of Chihuahua, has a surface of 27,000 ha from which 58% are saline-sodic soils. Also, the former Texcoco lake region, nearby Mexico City, presents salinity and sodicity problems that have a negative impact in the local environment. As a measure of reclamation, alkaline biosolids were applied to saline-sodic soils from the Valley of Juarez, while acid biosolids (treated with peracetic acid) were applied to Texcoco soils. When lime treatment was applied, faecal coliformes and helminth ova were reduced from 7.3x10⁶ MPN/g TS and 127 ova/g TS to <300 MPN/g TS and 5.5 ova/g TS, using a dose equivalent to 23.8% of quicklime. In contrast, acid treatment reduced faecal coliformes and helminth ova from 2.5x10⁸ MPN/g TS and 48 ova/g TS to 3.9x10⁵ MPN/g TS and 18 ova/g TS. Biosolids were then applied to columns containing the individual soils at different rates: alkaline biosolids were applied at a dose equivalent to 50 times the agronomic rate for cotton, while the acid biosolids were applied at doses equivalent to the agronomic rate for grass and 10 times such rate. In both cases the agronomic rates were determined based on the nitrogen requirements of the crops.
With the application rate of 340 ton/ha of limed biosolids, the exchangeable sodium percentage (ESP) was reduced approximately 85% and the sodium adsorption ratio (SAR) was lowered approximately 96%. The biosolids applied in one of the soils tested increased its permeability and the leaching of cations, which in turn helped to drain out the salts. The use of limed biosolids enhanced the cation exchange between sodium and the calcium contained in them. The conditions of the reclaimed soils from the Valley of Juarez suggest that crops that do not necessarily are adapted to saline-sodic soils may be used, allowing the farmers to grow products other than cotton.
In the case of the acid biosolids, and based on the soil microflora, the application of biosolids to Texcoco soils did not present a negative effect considering bacteria, fungi, and actynomicetes. Moreover, the addition of organic matter and the incorporation to the soil favoured the aggregation of the clays contained in these types of soils, thus increasing the aeration, permeability and water retention capacity. There were no apparent cation exchange in this part of the experimental work, as noted by an increase in the sodium adsorption ratio after the application, especially with the reclamation rate of 175 ton/ha since there were no calcium available for substituting sodium cations. Even when the columns received only irrigation water (i.e. no biosolids), the SAR increased in 156% due to the dissolution of minerals present in the soil. The leaching of sodium from the system was higher when the agronomic rate was used and lower when the reclamation rate was applied. Apparently, this was produced by the large amount of organic matter added with the biosolids, which having a negative charge represents additional sites for sodium to be adsorbed. With respect to electrical conductivity, in all the cases it was reduced from 6.9 mmhos/cm in the dry soil, to less than 4 mmhos/cm in the irrigated and amended soils.
Comparing the results of both experiments, it is clear that an adequate drainage together with a source of calcium is needed to reclaimed saline-sodic soils. In the case of alkaline biosolids, the calcium comes from the lime used in the stabilisation process while in the acid biosolids there was no calcium available. However, the use of these biosolids may be coupled with a calcium-rich waste to allow such exchange.

26.

Crop Production and Land Reclamation Utilizing Biosolids

as Soil Amendment
J.C., Martínez¹; L.H., Romero¹ and E.S., Olivares ^2
1 Servicios de Agua y Drenaje de Monterrey. Matamoros #1717 Col. Obispado Monterrey, N.L. Mexico C.P. 64010. e-mail: [e-mail]

² Centro de Investigaciones Agricolas Fac. Agronomia U.A.N.L. Km #17 Carr. ZuaZua-Marin, Marin N.L. Mexico. C.P. 66700. E-mail:[e-mail]

ABSTRACT

Introduction:

Even though drinking water treatment plants have been established since long ago (1965) in the Metropolitan Area of Monterrey, Mexico, wastewater treatment plants are relatively new, in fact, the first wastewater treatment plant with a secondary treatment begun its operation until 1995. That same year two additional plants were put in operation with a total treatment capacity of 8,784 lps (liters per second), at the moment we are treating 6,144 lps with an effluent quality that meets the Mexican Regulation for effluent discharge. Until December 2000, the biosolids obtained as a sub-product of wastewater treatment had to be confined in a landfill owned by the wastewater treatment plant with a daily mean production of 150 dry tons. Biosolids utilized as soil amendment in semi-arid soils in the Northern part of Mexico which have pH above 8.0 can improve crop yield, help establish urban parks in soil that have no other use such as trash landfills or land with low organic matter and nutrient availability.

Important consideration such as soil conditions, biosolid quality, crops grown and rate of application are the most important characteristics that should be included in a complete research in biosolids. The general objective of this research is to evaluate biosolid in crop production and land reclamation for urban parks and nurseries.
Crop Production:

The research was conducted in the Agricultural Experiment Station of “Servicios de Agua y Drenaje de Monterrey” located in “Dulces Nombres” Wastewater Treatment Plant located at the municipality of Pesqueria, N.L. Mexico. The research was conducted from August 1998 through June 2000 with the objective to determine the environmental and economical feasibility of Class “B” biosolid utilized as soil amendment. Fourteen different species including grains (wheat, sorghum, maize and bean) and vegetables (tomato, jalapeno pepper, serrano pepper, cucumber, cantaloupe, coriander, squash, broccoli, cabbage and cauliflower) were sown in four plots under a complete block random design with five treatments in four replications. Treatments consisted in dewatered biosolid 4 dry t ha^-1, dewatered biosolid 8 dry t ha^-1 and liquid biosolid 8 dry t ha^-1 amended one month before first crop was sown in each plot and at no other sowing season was the amendment repeated. These treatments were compared with inorganic fertilizer applied at each season according to its recommendation rates and control which consists on soil as is. Residual effect throughout several sowing seasons in four plots and a one time application of biosolid was evaluated in a total area of four hectares.

Data collected consisted in crop yield, essential (copper and zinc) and non-essential elements (cadmium, lead and nickel) concentration in leaves, edible portion of crops and soil at a depth of 0-30 cm. Statistic analysis was conducted for yield, but not for essential and non-essential element concentration.

It was concluded that highest yields were obtained during the first season, when liquid biosolid 8 dry t ha^-1 was amended, but dewatered biosolid 8 dry t ha^-1 was superior compared with the rest of the treatments in the second, third and fourth sowing season,. Therefore, residual positive effect in crop yield was observed even after four sowing seasons with a one time amendment of biosolids.

Regarding essential elements results indicated increased zinc concentration in leaves when dewatered biosolid was amended. Results also indicated that total and extractable zinc was increased in soil when liquid and dewatered biosolid 8 dry t ha^-1 was amended, but were below tolerance limits.

Non-essential elements or heavy metal concentration in leaves, fruit and soil were below tolerance limits in all treatments. Therefore, it is safe to amend liquid or dewatered biosolid in the dosage, crops and sowing seasons studied in a soil with a pH close to 8.0.

Biosolid Registration:

In July 2000 “NUTRIREGIO” was registered as the commercial name for our biosolid, recommended to improve soil fertility. Biosolid characterization and research results regarding biosolid heavy metal concentration and pathogen content, crop yield, metal concentration in edible portion and soil were solicited in order to evaluate and authorize the use of biosolids as soil amendment. By December of the same year our product obtained the certification by the Federal Health, Environment and Agriculture Agencies. We are the first company in Mexico granted with this certification in order to beneficially apply biosolids as a soil amendment.

Urban Parks and Nursery:

Nursery.-We have a national pilot nursery project growing 100,000 native trees with ¼” caliper using biosolid as media, these trees have the intention of creating urban parks. The nursery has a flood irrigation system using reclaimed water as source from the “Dulces Nombres“ Wastewater Treatment Plant, therefore a recycled integrated system is applied due to biosolid and reclaimed water exploitation.

Urban Parks.- We have begun two urban parks which uses as media a mixture of native soil plus biosolid in pits, in order to improve soil fertility and enhance tree growth. Native trees such as Pithecellobium flexicale, Quercus sp., Prosopis glandulosa, Parkinsonia aculeata, Acacia fernesiana, Ehtreria anacua, Cordia boissieri, Celtis laevigata and Carya illinoinensis which can be found in our natural vegetation are the best candidates in order to have the maximum survival, growth and less maintenance because these plants are resistant to water stress, local pests, climate and regional soils. Native trees grown will help the Metropolitan Area of Monterrey environment, which has been suffering of constant deforestation as population grows.
INDEX WORDS
Biosolid, essential elements, non-essential elements, nutrients, nursery, urban parks
27.

BIOREMEDIATION OF SANDY SOIL FERTILIZED BY BIOSOLIDS

FOLLOWING PHENOL SPILLS

N. I. Galil and H. Mamane

Department of Civil Engineering, Technion – Israel Institute of Technology, Haifa 32000, Israel

Tel: [phone]; Fax: [phone]; E-mail: [e-mail]..il

ABSTRACT
The study focuses on the fate of phenol, in cases of industrial wastewater uncontrolled spills, over sandy soil, which has been previously fertilized by treated biosolids, from municipal wastewater treatment plants. The presence of biosolids in the upper region of the soil could be somehow expected to enhance the biodegradation of organic contaminants originating from the uncontrolled spills. In these conditions, as the contaminated site has to be cleaned-up, it is important to clarify if there is any contribution of the biosolids to the bioremediation of the contaminated soil.

The study was based on continuous flow experiments, which were conducted on 5 cm diameter columns, packed with sandy soil, containing raw or stabilized biosolids on the top. For comparison purposes, columns without biosolids were also operated. Concentrated solutions of phenol were applied on the top of the soil, simulating accidental spills. A constant volume of aqueous solution, enriched by nitrogen, phosphorous and potassium nutrients, was continuously recycled at constant flow, from the top to the bottom, through the contaminated columns, simulating in-situ bioremediation. Concentrations of phenol, TOC, dissolved oxygen and turbidity were monitored daily.
The experiments indicated the need for an acclimation period, before the bioregeneration process started. This period was in the range of 100 to 200 hours according to the phenol initial loading and the stability of the biosolids applied on the top of the soil. Batch controlled contact experiments indicated low sorption of phenol onto the biosolids. Due to the low sorption exerted by the biosolids, it could be assumed that the phenol reduction was achieved mainly by biodegradation mechanisms.
The results show that the presence of biosolids on the top of the soil did not enable better biodegradation rates of the organic contaminant, in this case phenol. The highest removal rates of phenol were obtained by the sand soil column, which was operated without the application of biosolids. This study indicated that stabilized biosolids, disposed as fertilizers on the top of sandy soil, did not facilitate the bioremediation process, in case of clean-up spills of pollutants, such as phenol.

28

Impact of the revision of the European Sludge Directive on recycling in agriculture

Florence Ducray, Lucie Patria. ANJOU RECHERCHE – VIVENDI WATER

Alain Huyard. CIRSEE – ONDEO SERVICES