The introduction of microorganisms with specific degradative capacities into the soil was shown to be a possible means of ridding the soil of contaminating chemicals. An investigation of the interactions of soil microorganisms and several groups of herbicidal compounds, primarily chlorinated derivatives, was made. In pure culture and in soils the addition of 2,3,5,6-tetrachloroterephthalate (DCPA) had little effect upon bacterial growth, and several microorganisms appeared to use the herbicide as a carbon source. The encouragement of the soil microflora by the addition of nutrient broths resulted in a reduction of toxicity to plants of a number of herbicides. Isopropyl N-phenylcarbamate (IPC) degrading organisms, when added to soil, accelerated the degradation of IPC and related compounds. A membrane 'biologicalilter' device for reducing waterborne biodegradable pollutants was also demonstrated using these organisms.

Diatoms comprise the major group of algae in Iowa waters. Their ecological significance, important in pollution evaluation studies, cannot be fully appreciated without a thorough knowledge of their taxonomy. A scale for abundance rating was used giving at least a rough estimate if data permitted. The names of 50 diatom genera occurring in Iowa are listed and for each genus, the number of taxa in the master list and the number in the 'more common' list are presented. A pollen analysis is tabulated; the samples in this analysis extended through 35 ft. of sediment to the postglacial interface at Little Miller's Bay, Lake West Okoboji. Dating was conducted by the radiocarbon technique for samples taken between 34 ft. and 35 ft. in the sediment core. Since this level had the maximum spruce pollen concentration and the pollen percentage decreased progressively above this level, it was considered as the postglacial interface. Some interesting problems lie in consideration of those diatoms which have disappeared from the original lake flora and those which have become common only since the middle of the postglacial period.

A survey of 452 eutrophic lakes was compiled based on responses from 40 states requesting information as to (a) Name, location, size, depth; (b) Description of the problem, including accounts of previous corrective treatments, if any; (c) Remedial action that might be appropriate; (d) A description of available background data, indicating whether sufficient data exists to document a change if rehabilitation were undertaken. Categories of the problems in the survey were: nuisance algal growth, nuisance aquatic vegetation, fishkills, bacterial contamination, toxic contamination, oil brines, unstable water levels, siltation, excessive dissolved solids, and unspecified eutrophic conditions. Sources contributing to these problems were classified in two general categories--concentrated sources and diffused sources. Indication is given, where available, whether progress has been made to eliminate the pollution source.

Two 100,000 gallon collapsible tanks were anchored under water in Lake Erie to demonstrate, on a pilot scale, the feasibility of storing combined sewer storm overflow in underwater flexible tanks. Site selection, model testing, system design, construction, and one year's operation were included in the investigation. During the year's operation, 988,000 gallons of storm overflow were contained and returned to the treatment plant for treatment. Construction, operation, and maintenance costs are discussed. It was determined that for larger installations, modular systems of 250,000 to 500,000 gallon basic unit tanks should be employed, with site characteristics determining both the overall feasibility of the system, and the optimum tank size should such a system be feasible. Life expectancy for tank materials can only be determined in full scale operation in the actual environment.

To aid in the further development of sewage treatment by activated sludge, a continuous flow automatically recording respirometer was used to study the response of aeration only and aeration with sludge return completely mixed activated sludge systems (CMAS) to step changes in the influent substrate. The experiments were conducted at 25 C with glucose; a mixture of glucose, glutamate, and acetate; and a mixture of sewage solids plus Metrecal. Influent substrate concentrations were doubled in the 3-hour and tripled in the 6-hour mean residence time aeration only experiments without increasing the soluble COD in the effluent. Decreases in the influent substrate concentrations produced rapid decreases in the rate of oxygen utilization. A procedure for calculating the rate of oxygen uptake by a CMAS system at any time during a step transient was developed.