BIOTHERMAL METHODS (grech, bios life + thermos warm) — methods of neutralization of the garbage containing the organic matters based on their warming up as a result of life activity of thermophilic aerobic microorganisms.
In the household garbage collected in big or rather large volumes at a condition of keeping in garbage of high percent of organic matters conditions for snowballing of various microorganisms are created (bacteria; mold fungi — Aspergillus, Thermomyces, Thermoiolium; some types of Mucor; actinomycetes — Actinomyces, Thermophilus), processes of breath and which fermentations are followed by calorification and temperature increase of the environment.
At achievement in the mass of household garbage of temperature 40 — 45 ° life of mesophilic flora stops. She gives way to thermophiles — microorganisms which are capable to breed quickly at temperature increase of household garbage to 60 — 70 ° (see. Thermophilic bacteria ). Warming up of mass of garbage under the influence of thermophilic microorganisms leads to death of larvae of flies, eggs of helminths and microflorae, including pathogenic. In process of use of digestible organic material reproduction of thermophiles is slowed down in the beginning, and then stops. At fall of temperature the place of thermophiles is taken again by mesophilic microorganisms.
B.'s efficiency of m of neutralization of solid household garbage is in direct dependence on aeration, humidity and a thermal conditions of the neutralized mass of garbage since the course of processes, the speed and completeness of neutralization and decomposition of organic matter of garbage, death of pathogenic microorganisms, eggs of helminths and larvae of flies is defined by these parameters. All these factors are interdependent. Excessive aeration of garbage can promote decrease in temperature and drying of the neutralized material that can lead to the termination of biothermal process since bacteria acquire substances necessary for them only in the form of aqueous solutions, and their life activity is in direct dependence on heating environments. Ensuring biothermal aerobic process demands receipt of a certain amount of oxygen of air in the mass of the neutralized material. The conditions stated above are reached by the content of garbage in a friable state and in the special rooms providing stability of a microclimate (an exception of overcooling, drying and excessive moistening at the expense of an atmospheric precipitation).
Preliminary crushing of household garbage positively affects a pas the course of biothermal process. Efficiency of biothermal process depends as well on character of the garbage intended for biothermal neutralization. Laboratory researches and practical observations indicate that the garbage intended for biothermal processing shall meet the following requirements: to contain apprx. 30% of quickly decaying organic matters (waste of food, excrement of the person, animals and birds, waste of a plant origin and so forth) and no more than 25% of the substances which are not giving in to rotting or fermentation (stones, metal objects, glass, slag, rubber, synthetics and so forth). Humidity of garbage can fluctuate within 40 — 75%. It must be kept in mind that obtaining the qualitative parameters of household garbage stated above can be reached in any of options at the expense of additives to them of dry organic waste, the dry crushed peat, etc. (at the increased their initial humidity) or addition of liquid sewage, drain waters, a silt deposit, etc. (at deficit of moisture).
In a crust, time the aspiration to industrial methods of neutralization and processing of household garbage is expressed. At the same time the m accelerated by B. on special installations, waste recycling plants with a complex of the intensified bioheat treatment, and also chemical and physical gain broad development. methods of neutralization.
Waste recycling plants. For the cities, and in some cases for group of the cities the mechanized waste recycling plants on which due to use of the methods accelerating biothermal processes (crushing of garbage, continuous hashing, air flushing), the term of neutralization is reduced to 3 — 5 days whereas at a composting of household garbage in usual null conditions are under construction (biothermal ditches, layer-by-layer stacking, etc.) its neutralization is reached in terms from 6 months up to 11/2 years and more depending on nature of the soil, the level of subsoil waters, climatic areas, etc.
Waste recycling plants found broad application in many European countries and in the USA. The first two large plants in the USSR became operational: the Leningrad's first garbage with a productivity of 120 — 140 000 t in a year, the Moscow's second garbage with a productivity of 200 000 t in a year. The plant has installation for burning of not punched part of garbage. Some more waste recycling plants in Tashkent, Riga, Minsk, Ryazan, Bitter and other cities are projected and under construction.
The continuity of work and start-up of garbage in a production cycle without preliminary warehousing is characteristic of the majority of modern types of waste recycling plants. Technical process of neutralization of garbage at these plants in the cycle has three main phases:
1) reception and preparation of garbage (sifting on coarse screens, crushing, release of metal magnetic separators);
2) biothermal processing in the rotating drums, tower installations, cameras etc.;
3) processing of compost (sifting, regrinding, release of glass). On separate types of the plants the first two cycles of processing are united in one. On some waste recycling plants depending on their throughput and character of household garbage waste incineration installations join.
Biothermal cameras — constructions for neutralization of organic garbage by biothermal methods. Unlike composts, biochemical processes in biothermal cameras proceed quicker, more intensively and at more high temperature. The first biothermal camera was constructed in 1912 in Florence by G. Beccari. The subsequent use of this method in various countries, including and in our country, was followed by various modification directed to reduction of overtime of garbage, mechanization of their loading and unloading and to a possibility of their year-round use in various climatic zones.
In any of modifications of the biothermal camera the main nodes are: rooms for the content of garbage, actually the camera from a tree, a brick or concrete with the device for its warming and aeration, with devices for loading and unloading of household garbage, for collecting and removal of liquid. The volume of cameras usually fluctuates from 2 to 40 m 3 .
Hymification and neutralization of household garbage in biothermal cameras come to an end quickly. Settlement turnover of the camera for a midland of the USSR is accepted in 60 days, and for southern — in 40. In more modern biothermal cameras process of neutralization comes to an end respectively in 40 and 20 days. The device of the biothermal camera is regulated by state standard specification 3743 — 47. Biothermal cameras are recommended for small settlements and separate objects: rest houses, sanatoria, etc.
Hotbeds — one of the elementary constructions on processing of household garbage and manure on the basis of B. of m. Originally hotbeds were considered and used as page - x. installation for receiving early fresh vegetables and greens. As biological fuel horse manure was usually applied. In the subsequent works of the Soviet scientists proved a possibility of use in hotbeds as biological fuel of city garbage. In the household garbage loaded into hotbeds there are same biochemical processes, as well as in biothermal cameras, only to smaller intensity. At the final stage household garbage turns into a humus which is not dangerous in a dignity. - epid, the relation is also good fertilizer for fields.
Hotbeds represent ditches of 0,8 m in depth, 1,5 m wide and up to 25 m long. Over a ditch the timbered felling on which the glazed frames keep within is established. The ditch is filled with household garbage a layer in 0,6 m with top filling by vegetable soil a layer in 15 cm. Household garbage is made usually during November — January and develops in stacks, and in February — April is put in hotbeds as biological fuel. In hotbeds the garbage is isolated, does not contaminate the gases free air and is unavailable to flies. Conditions of processing of household garbage allow to carry hotbeds to group of constructions on biothermal neutralization. The method has a number of shortcomings. Preparation of a hotbed for work creates a number sanitarily of the adverse factors caused by need of preliminary accumulation on the open area in hotbeds of household garbage that occurs during the period from November to February. Vneshneploshchadochny accumulation of household garbage during the specified period of year creates pollution of the air basin and conditions for a mass existing of rodents. The same phenomena are noted also during release of hotbeds from a humus. The received humus usually contains the objects (metal, glass) which did not undergo disintegration. Process of work at preparation of household garbage and stuffing of hotbeds is unsafe in a dignity. - epid, the relation and labor-consuming, especially in need of use of a large amount of garbage on big squares. Development of hothouse and greenhouse economy in our country on the basis of mechanization of work and automation of many processes caused need of transfer of greenhouses and hotbeds on technical heating.
See also Composting .
Bibliography: Arzamasova Z. A., etc. The mechanized biothermal neutralization and waste recycling in fertilizer, in book: The main vopr. dignity. protection of the soil, under the editorship of V. A. Gorbov, etc., page 284, M., 1965; Gulyaev Η. T. Sanitary cleaning of the cities in the USSR and abroad and perspectives of its development, in the same place, page 51; Shapiro M. A. and Kuzmenkova A. M. The accelerated waste recycling and use of compost abroad, page 5, M., 1964, bibliogr.
P. M. Vindyukov.