Filamentous bulking sludge--a critical review.

Processes and compositions are provided for decreasing emissions of mercury upon combustion of fuels such as coal. Various sorbent compositions are provided that contain components that reduce the level of mercury and/or sulfur emitted into the atmosphere upon burning of coal. In various embodiments, the sorbent compositions are added directly to the fuel before combustion; are added partially to the fuel before combustion and partially into the flue gas post combustion zone; or are added completely into the flue gas post combustion zone. In preferred embodiments, the sorbent compositions comprise a source of halogen and preferably a source of calcium. Among the halogens, iodine and bromine are preferred. In various embodiments, inorganic bromides make up a part of the sorbent compositions.

Reducing mercury emissions from the burning of coal

In a wastewater treatment plant, the liquid side of the plant has preferably four stages for nitrification and/or denitrification, prior to further treatment such as a clarifier. Energy requirements are reduced by reducing aeration requirements. Four or more tanks/zones comprise serial anoxic and aerobic stages, but in the anoxic stages simultaneous nitrification/denitrification takes place in accordance with the known process of U.S. Pat. No. 5,906,746. By this arrangement the system can achieve a volume ratio of about 20% aerobic tankage to the total tankage volume, as compared to a much higher ratio in a typical prior art system of serial aerobic/anoxic stages, and greatly reducing aeration requirements.

Energy efficient wastewater treatment for nitrogen and phosphorus removal

A high-rate biological waste water treatment process for removing organic tter, phosphorus and nitrogen nutrients from municipal waste water comprising the steps of mixing the influent waste water in an initial anaerobic reactor zone to maintain the biological solvents in suspension with a denitrified mixed liquor from a downstream anoxic reactor zone, typically at a flow rate of 0.5 to two times the waste water flow rate. The reactor zone serves to select microorganisms capable of accumulating quantities of phosphorus in excess of that required for simple cell growth and reproduction. The phosphorus removal occurs due to the removal of excess sludge (waste activated sludge) produced in the process wherein such sludge can be removed from the clarifier underflow or as a mixed liquor directly from the biological reactor.

High-rate biological waste water treatment process using activated sludge recycle

A wastewater treatment process providing nitrogen, phosphorus, biochemical oxygen demand, and suspended solids removal. The process includes the sequential steps of passing wastewater (3) mixed with recycled activated sludge (32) from a subsequent settling step (30) into a first anoxic zone (10), to a first aerobic zone (15) and then to a second anoxic zone (20), recycling a stream (16) from the first aerobic zone (15) to the first anoxic zone (10), introducing volatile fatty acid (21) into the second anoxic zone (20), and settling the effluent (22) from the second anoxic zone (20) into a purified wastewater (36) and a sludge (33), a portion of which is recycled to the first anoxic zone (10).

Wastewater treatment process

An organic product material having a high nitrogen and phosphorous content is produced as the product of a biological system for the treatment of a BOD-containing influent which also contains phosphorous and fixed nitrogen. The biological treatment system comprises the reaction of a mixed liquor composed of an activated biomass and a BOD-containing influent initially under anaerobic conditions and thereafter treating such mixed liquor under oxic conditions. The treated material is then separated into a supernatant liquid in which the BOD is depleted and a dense, activated biomass. A portion of this biomass is employed in forming the mixed liquor for the initial anaerobic treatment, while the remaining portion of the biomass is recovered as product. The living biomass product can be used in the fermentation industries. Alternatively, the product can be used as such or further processed, e.g. dried, for employment as a fertilizer or a nutrient in animal feeds.

High nitrogen and phosphorous content biomass produced by treatment of a BOD-containing material

The treatment of wastewater with activated biomass to remove BOD and phosphorus values in a system in which the wastewater influent is initially mixed with recycled active biomass in an anaerobic zone and then subjected to aeration in an oxic zone, wherein the residence time of the mixed liquor in the oxic zone is reduced. At least part of the biomass-containing sludge separated from the mixed liquor subjected to further oxidation in a separate zone before admixture with the wastewater influent.

Removal of phosphates and BOD from wastewaters

Heating values are recovered from sulfur-containing coal in a reactor which includes a gasification zone, a combustion zone and a heat recovery zone. A fluidized bed of coal and limestone is maintained within the gasification zone, which is supported by a moving foraminous grate. Primary air, which is also the fluidizing medium, enters the gasification zone through the grate. The zone is operated adiabatically, under reducing conditions, to yield CaS and an effluent rich in CO. The CaS is discharged from the gasification zone by the moving grate and the gaseous effluent, containing entrained desulfurized coal fines, enters the combustion zone where secondary air is added. The exotherm of combustion is retrieved in the heat recovery zone, using conventional techniques. The flue gas from the reactor contains little sulfur dioxide to pollute the environment. The CaS may be processed in several ways to recover elemental sulfur.

Combustion of high-sulfur coal in a fluidized bed reactor

Heating values are recovered from sulfur-containing coal in a two-stage process which minimizes pollution. In the first stage, sulfur-containing coal is reacted with CaO in a fluidized bed gasifier which operates adiabatically, under reducing conditions, to yield CaS and a gas rich in CO. The second stage is a conventional boiler to which the off-gas from the first stage and entrained desulfurized coal fines, are delivered as fuel. The flue gas from this boiler contains substantially no sulfur dioxide as a pollutant. CaS is withdrawn from the first stage as a valuable byproduct.

Combustion of high-sulfur coal with minimal ecological trauma

OF THE DISCLOSUREA modified activated sludge system is provided wherein wastewater containing BOD and phosphate values is admixed with biomass-containing recycled sludge under conditions effecting sorption of BOD in the biomass, then said wastewater is subjected to aeration in an oxidation zone under conditions effecting oxidation of BOD, including a dissolved oxygen level in said zone of less than one part per million. By such operation, considerable savings in power requirements for oxygen transfer to the mixed liquid are had, while developing and maintaining a dense non-bulking biomass having the properties of good removal of phosphate from the waste-water influent. By operating the system at high influent throughput rate (F/M), external oxygen requirement for BOD removal is minimized.

Marshall Louis Spector

Papers

High nitrogen and phosphorous content biomass produced by treatment of a BOD-containing material

Removal of phosphates and BOD from wastewaters

Combustion of high-sulfur coal in a fluidized bed reactor

Combustion of high-sulfur coal with minimal ecological trauma

Biological wastewater treating system