Raymond C. Loehr

Toxicity of metals to the earthworm Eisenia fetida

SummaryDevelopment of methods to measure the effect of mans residuals on soil ecosystems is desirable. Earthworms, as one of the largest and most easily obtained components of the soil biota, are suitable for evaluating perturbations to soil ecosystems.The impact of five metals (Cd, Cu, Ni, Pb, and Zn) on the survival of the earthworm Eisenia fetida (Savigny) was evaluated using the contact and artificial soil tests. There was no difference in toxicity between the different metal salts (acetate, chloride, nitrate, and sulfate) of each of the five metals using the contact test. In the contact test, the order of toxicity, from most toxic to least toxic, was Cu > Zn > Ni ≈ Cd > Pb. The nitrate salt of the five metals was tested using the artificial soil test and the order of toxicity, from most toxic to least toxic, was Cu ≈ Zn ≈ Ni > Cd > Pb. Stress on earthworm populations, as shown by weight loss, was shown to increase with increasing concentrations of metal salts.These studies indicate that: (a) earthworms can be a suitable biomonitoring tool to assist in measuring the effect of metals in wastes added to soils and (b) the contact and artificial soil tests can measure the biological impacts.

Microbial nitrification and denitrification in concentrated wastes

The feasibility of removing nitrogen from a concentrated nitrogenous waste by microbial nitrification and denitrification is investigated. Continuous flow and batch studies have been conducted to investigate the effect of the various parameters that affect the process of nitrification. A solids retention time of greater than two days and a range of loading factors between 0.15–0.84 #COD day−1 #MLVSS−1 resulted in 45–60 per cent nitrification of the total Kjeldahl nitrogen contained initially in the waste. The level of inhibition of nitrification due to free NH3 and undissociated HNO2 is discussed. The control of pH was found to be unnecessary either in nitrification or denitrification of the waste. Denitrification of the nitrified waste resulted in complete elimination of the oxidized nitrogen formed in the nitrification stage; nevertheless, residual ammonia contained initially in the mixed liquor persisted. A second nitrification of this denitrified mixed liquor resulted in complete oxidation of the residual ammonia.

Kinetics of microbial nitrification: nitrite-nitrogen oxidation

Abstract The kinetics of nitrite-nitrogen oxidation by enriched Nitrobacter cultures were examined under various temperatures (9°–35°C), pH (6.0–8.5), and microbial concentrations. For the substrate concentrations examined (100–1100 mg N1−1) the reaction was zero order and correlations between temperature, pH, microbial concentrations and reaction rates were formulated. Inhibition by free ammonia and nitrous acid is discussed. This study of enriched cultures of nitrobacter organisms also provide some insight into the growth characteristics of this fastideous organism under conditions of dense population and severe environmental conditions (temperature and pH).

Factors affecting the vermistabilization process: Temperature, moisture content and polyculture

Vermistabilization is the stabilization of organic wastes using earthworms. The worms maintain aerobic conditions in the wastes and accelerate and enhance the biological decomposition of the wastes. This study evaluated several fundamental factors that affect the performance of the process such as temperature, moisture content of the waste material and the combined use of several earthworm species (polyculture). The earthworms Dendrobaena veneta, Eisenia fetida, Eudrilus eugeniae, Perionyx excavatus and Pheretima hawayana were used in one or more of the studies. The best growth and reproduction of these species occurred at temperatures of 20–25°C. Growth of all five species was reduced at 30°C and death occurred at 35°C. Of the five species, E. fetida produced the largest number of young in a 20 week study. The growth of E. fetida occurred optimally in media with a total solids content, wet basis, of between 9–16%. Polyculture did not have any obvious advantages over monoculture.

Animal manures as feedstuffs: Nutrient characteristics

Abstract This study critically evaluates the potential value of animal manures as feedstuffs for livestock and poultry using information in the published literature. The paper provides an assessment of the nutrient and economic value of manures as a function of their composition when compared with conventional feedstuffs. Subsequent papers provide an assessment of the value of manures based upon animal performance in feeding trials. The information presented in this paper indicates that dried poultry waste (DPW), broiler litter, dairy cow manure and beef cattle manure are most comparable to forages, rather than to energy or protein feeds, when utilised as ruminant feedstuffs. When DPW is utilised as a feedstuff for laying hens it is best considered as a source of minerals and amino acids.

Changing practices in agriculture and their effect on the environment

With less man hours and acreage per production unit, agricultural productivity has increased significantly. The increased efficiency has been associated with a number of environmental quality problems. This review emphasizes animal production as an example of the changes that have occurred in agriculture. The major topic areas include land disposal of wastes, runoff, odors, water pollution, and waste management.

Animal Manures as feedstuffs: Poultry manure feeding trials

Abstract The utilisation of dried poultry manure as a feedstuff was critically evaluated based upon feeding trial results reported in the literature. The assessment indicated that this material can have value as a feedstuff. The maximum and optimum levels of incorporating dried poultry manure into laying hen and ruminant rations, on the basis of animal performance, varied from 5% to about 20% of a ration. Generally, the maximum level for incorporating dried poultry manure into rations was less than 20%. Dried poultry manure was found to have a monetary value as a feedstuff that equalled or exceeded its value as a fertiliser.

Animal manures as feedstuffs: Broiler litter feeding trials

Abstract The use of broiler litter as a feedstuff was evaluated on the basis of results of feeding trials reported in the literature. Although the method of preparing or processing the broiler litter as a feed constituent (drying, composting or ensiling) influences its value, this assessment indicated that broiler litter has value as a feedstuff. The maximum level of incorporating broiler litter into ruminant rations, on the basis of animal performance, varied from 1% to about 50% of a ration. Generally, the optimum level of incorporating broiler litter into rations was less than 20%. However, it was incorporated at higher levels without adversely affecting animal performance. Broiler litter had an economic value as a feedstuff that equalled or exceeded its value as a fertiliser.

Treatment of poultry manure wastewater using a rotating biological contactor

Abstract A pilot scale, six stage rotating biological contactor was used to evaluate the feasibility of this process for the stabilization of liquid animal manures. Total disc surface area was approx. 16.7 m 2 . Treatment efficiencies were determined at various waste strengths and influent flow rates. With loading rates of 14.7–322 g m −2 day −1 , the average COD reduction was 61%. With loading rates of 4.88-24.4 g m −2 day −1 , the average BOD 5 reduction was 87%. Total nitrogen removal averaged approximately 30% for the entire study. Mixed liquor oxygen uptake rates were generally in excess of 80 mg 1 −1 h −1 . Clarified effluent was non-odorous and suitable to be reused for manure flushing or spray irrigation. Treatment was not sufficient to permit effluent discharge to surface waters.

Comparison of the conventional cage rotor and jet-aero-mix systems in oxidation ditch operations

Abstract The Jet-Aero-Mix system, designed on the basis of Fannings for Darcys Equation, was tested at the USDA Fur Animal Research Farm at Cornell. Oxygenation studies with tap water showed fairly good comparison with that of a conventional cage-rotor system, and the performance with mink waste resulted in high degrees of treatment. From a general maintenance standpoint, the Jet-Aero-Mix (JAM) system does not have the problems of bearings and belt slippage associated with a cage rotor. One potential problem still exists and would be resolved only by testing. The problem is the possibility of plugging the nozzles by strawlike materials such as large feathers and straw bedding from cattle. From an economic standpoint the operating cost of the JAM system (in terms of energy consumption) is comparable to that of the cage rotor. The capital expenditure offers substantial savings. Because of the simplicity of this device, the JAM system also offers the flexibility of being able to be installed in phases to meet the desired quality of treatment, especially in large systems where fairly large initial capital outlay may be required. Based on the oxygenation studies, economic analysis and field testing with mink waste, the JAM system appears a reasonable alternative to a cage rotor for aeration and mixing in an oxidation ditch process. The system appears to be especially useful for small systems and should receive consideration in situations where aerobic treatment is contemplated.