In the processes for treating municipal sewage and storm water containing biosolids to discharge standards, biosolids, even after dewatering, contain typically about 80% water bound in the dead cells of the biosolids, which gives biosolids a negative heating value. It can be incinerated only at the expense of purchased fuel. Biosolids are heated to a temperature at which their cell structure is destroyed and, preferably, at which carbon dioxide is split off to lower the oxygen content of the biosolids. The resulting char is not hydrophilic, and it can be efficiently dewatered and/or dried and is a viable renewable fuel. This renewable fuel can be supplemented by also charging conventional biomass (yard and crop waste, etc.) in the same or in parallel facilities. Similarly, non-renewable hydrophilic fuels can be so processed in conjunction with the processing of biosolids to further augment the energy supply.

Slurry dewatering and conversion of biosolids to a renewable fuel

Systems and methods for wastewater treatment. A nitrate source may be dosed to a collection tank, such as a wet well, for downstream control of hydrogen sulfide levels in the wastewater. A source of a strong oxidizer may also be dosed to the wet well. The oxidizer, such as chlorite, may temporarily interrupt denitrification processes in the wet well to prevent floatation of undesirable constituents therein. The oxidizer dosage may be generally consistent with the nitrate dosage. An ORP sensor may facilitate regulation of dosing. The nitrate and the oxidizer may be present in a single mixture to be dosed to the wet well.

Wastewater treatment systems

A method and apparatus for treating wastewater streams by adding, either separately or as a mixture, a nitrate containing compound and an alkaline material in an amount sufficient to achieve a lower concentration of atmospheric hydrogen sulfide and dissolved sulfides downstream of the addition as compared to the atmospheric hydrogen sulfide and dissolved sulfides present in the wastewater stream prior to the addition. By adding alkaline material in addition to a nitrate containing compounds, the amount of nitrate containing compound added can be reduced by at least 10% as compared to the amount of nitrate that would theoretically need to be added in the absence of alkaline material to achieve a comparable lower concentration of atmospheric hydrogen sulfide and dissolved sulfides in the wastewater stream.

Methods and apparatus for reducing nitrate demands in the reduction of dissolved and/or atmospheric sulfides in wastewater

A wastewater treatment system and method for substantially reducing or eliminating total suspended solids (TSS), biological organic discharge or biochemical oxygen demand (BOD), and fats, oils and greases (FOG) contaminants. The system includes at least one mixing chamber for mixing wastewater with at least one dewatering agent or chemical and air to form an aerated mixture and at least one tank having a plurality of compartments for facilitating flotation, settling and removal of contaminants from the aerated mixture as it flows through the tank. Preferably, the system includes first and second mixing chambers and first and second tanks arranged in series with each of the tanks including drag lines for removing floating and settled contaminants.

Wastewater treatment system and method

Water (2) contaminated with at least one volatile compound is treated by air stripping (4) the volatile compound into the gas phase (6), then removing the volatile compound from the gas phase (12) by contacting (30) it with an aqueous slurry of powdered adsorbent, preferably mixed with biological solids. The partially-purified water (10) is further treated by a biophysical aerobic process (14) which in turn produces the aqueous mixture of biological solids and powdered adsorbent (28) used to remove the volatile compound from the gas phase. The aqueous mixture of biological solids and powdered adsorbent (48) containing the volatile compound is thickened (38) and the solids slurry treated by regeneration, preferably wet air oxidation, to destroy the biological solids and volatile compound as well as regenerate the powdered adsorbent (46). The regenerated adsorbent may be returned to the biophysical aerobic treatment process (14).

Process for treatment of water containing volatile and toxic compounds

Regenerated adsorbent particles, such as activated carbon, are recovered from a wet oxidation-regenerated mixed sludge liquor from a wastewater treatment system by diluting and settling a blowdown slurry (20) from the wet oxidation reactor (12) to obtain a first aqueous phase (32) containing primarily regenerated adsorbent particles and fine ash particles and a first solids phase (28) containing primarily grit particles. The first aqueous phase (32) is combined with a portion (16) of the regenerated adsorbent particle slurry withdrawn from the upper portion of the wet oxidation reactor (12) and, after treatment with a dispersing agent (36) and then an anionic flocculating agent (44), the resulting mixture (46) is settled to obtain a second aqueous phase (54) containing primarily fine ash particles and a second solids phase (50) containing primarily regenerated adsorbent particles. The second solids phase (50) is recycled to the wastewater treatment system for re-use and, after treatment with a cationic flocculating agent (58), the second aqueous phase (54) is settled to obtain a substan­tially particle-free third aqueous phase (66) and a third solids phase (64) containing primarily fine ash particles. Slurries (28) and (64) containing the grit and fine ash particles are combined and dewatered prior to disposal.

Process for recovering regenerated adsorbent particles and separating ash therefrom

A process for treatment of caustic sulfide liquor by wet oxidation in a nickel-based alloy system is described. The liquor is first analyzed for alkalinity consuming species and for nonsulfidic alkalinity. If excess alkalinity consuming species is present compared to nonsulfidic alkalinity, then additional nonsulfidic alkalinity is added to the raw liquor such that excess alkalinity is present during wet oxidation treatment, thus preventing excessive corrosion to the nickel-base alloy system.

Caustic sulfide wet oxidation process

A process for treatment of caustic sulfide liquor by wet oxidation in a ferrous-based alloy system at temperatures less than about 175° C. is described. The liquor is first analyzed for alkalinity consuming species and for nonsulfidic alkalinity. If excess alkalinity consuming species is present compared to nonsulfidic alkalinity, then additional nonsulfidic alkalinity is added to the raw liquor such that excess alkalinity is present during wet oxidation treatment, thus preventing excessive corrosion to the ferrous-base alloy system.

David A Beula

Papers

Process for recovering regenerated adsorbent particles and separating ash therefrom

Caustic sulfide wet oxidation process

Low temperature caustic sulfide wet oxidation process

Low temperature wet oxidizing process for caustic alkali sulfide

Process for recovering regenerated absorbent particles and for separating ash therefrom