Melvin S. Finstein

Microbiology of Municipal Solid Waste Composting

Publisher Summary This chapter focuses on the components of municipal waste which are compostable. Composting is the microbial degradation of organic solid material that involves aerobic respiration and passes through a thermophilic stage. It yields the stabilized end-product compost. Various solid waste management objectives can be achieved through composting, including sanitation, mass and bulk reduction, and resource recovery. Compost plays a unique role in certain specialized practices, including hotbed gardening, which requires self-heating organic matter, and as a substrate for edible-mushroom cultivation. For these purposes compost derived from municipal solid waste can substitute for the traditional horse manure preparation. Compost can be an economic soil conditioner for high-value crops, such as vegetables and flowers grown out of season. The chapter reveals that there are many proprietary processes for the treatment of municipal solid waste by composting, which offer a variety of mechanical and structural approaches to the problems of aerating and mixing the composting mass. From a microbiological viewpoint, only two major process variants are evident: batch and continuous composting.

Biological removal of gaseous ammonia in biofilters : Space travel and earth-based applications

ABSTRACT Gaseous NH3 removal was studied in laboratory-scale biofilters (14-L reactor volume) containing perlite inoculated with a nitrifying enrichment culture. These biofilters received 6 L/min of airflow with inlet NH3 concentrations of 20 or 50 ppm, and removed more than 99.99% of the NH3 for the period of operation (101, 102 days). Comparison between an active reactor and an autoclaved control indicated that NH3 removal resulted from nitrification directly, as well as from enhanced absorption resulting from acidity produced by nitrification. Spatial distribution studies (20 ppm only) after 8 days of operation showed that nearly 95% of the NH3 could be accounted for in the lower 25% of the biofilter matrix, proximate to the port of entry. Periodic analysis of the biofilter material (20 and 50 ppm) showed accumulation of the nitrification product NO3 - early in the operation, but later both NO2 - and NO3 - accumulated. Additionally, the N-mass balance accountability dropped from near 100% early in the experiments to ~95 and 75% for the 20- and 50-ppm biofilters, respectively. A partial contributing factor to this drop in mass balance accountability was the production of NO and N2O, which were detected in the biofilter exhaust.

Hydrolysis of condensed phosphates during aerobic biological sewage treatment

Abstract In a domestic sewage, the concentrations of orthophosphate and inorganic condensed phosphate varied widely during a 24-hr period. The condensed phosphate concentration was especially variable, increasing from 1 to 17 mg P/l during a 4-hr span. This increase coincided with an increase in the concentration of ABS. In the settled sewages sampled, approximately half the phosphorus was in the form of condensed phosphates. Treatment at activated sludge and trickling filter installations affected the hydrolysis of a portion of the incoming condensed phosphates. The extent of hydrolysis was variable, but in general, approximately half the condensed phosphates in the settled sewage was converted to orthophosphate during aerobic biological treatment.

The question of nitrification in the Passaic River, New Jersey: Analysis of historical data and experimental investigation

Abstract Historical NH 4 + and NO 3 − data from six stations on the Passaic River, New Jersey, were analyzed. The data for five of the stations span 1963 to 1976, and for the sixth station 1947 to 1976. Some of the conclusions reached are as follows: 1. (1) The concentration of NH 4 + fluctuated widely, but the trend was towards an increase with time. 2. (2) The concentration of NH 4 + was elevated during a period of extreme drought (1963 to 1966). 3. (3) The concentration of NO 3 − tended to increase smoothly with time. 4. (4) The concentration of NH 4 + increases longitudinally (with downstream travel). 5. (5) The loads (concentration × stream-flow) of both nitrogen species tended to increase with time. 6. (6) Substantial NO 3 − enters the stream from non-point sources. 7. (7) The potential for instream nitrification is not fully realized, as represented by elevated levels of NH 4 + . Item (7) was puzzling because conditions in the Passaic, especially in the summer, appear to be favorable for nitrification. The point was clarified, in part through an experimental investigation. River water samples, with and without added NH 4 Cl, were incubated, and the course of the first step of nitrification was followed through the appearance of NO 2 − . (The second step of nitrification was inactive during the experimental period.) The added NH 4 Cl enhanced nitrification in samples from the uppermost stations (native NH 4 + -N approximately 0.1 mg l −1 , but had little or no effect in samples from the middle and lower reaches (native NH 4 + -N > 0.5 mg l −1 ). Consequently, it was inferred that over most of the rivers mainstem the growth of NH 4 + -oxidizing bacteria was not substrate limited. There was also no indication of other nutrient limitations or of the presence of any inhibitors. This led to a projection of a 60-fold increase in the population density of planktonic NH 4 + -oxidizers over a certain stretch of the river. However, no increase in the most-probable-number (MPN) of NH 4 + -oxidizing bacteria was observed, which is consistent with item (7). In fact, at the end of a quiescent segment of the river the MPNs were anomalously low. This is attributed to the removal of cells from the water column through settling. This reasoning is extended to suggest that, throughout the river, settling may be the mechanism preventing a response of planktonic nitrifiers to the enrichment with NH 4 + from pollution sources. In turn, this could prevent a full expression of the potential for nitrification. The analyses are discussed from a regulatory perspective. It is concluded that the nitrification component of the Passaics self-purification capacity is overburdened, and first became so in 1953.

Relationships of autotrophic ammonium-oxidizing bacteria to marine salts

Abstract Autotrophic ammonium-oxidizing cultures were obtained from fresh, estuarine and littoral waters and tested for responses to marine salts. Some of the cultures did not require the salts for growth, whereas others failed to develop in their absence. Different degrees of salt tolerance were noted among the non-requiring group.