Wastewater containing a significant level of dissolved readily biodegradable organic compounds matter, such as short-chain fatty acids, and ammonia can be efficiently treated to remove most or all of the organic compounds and the ammonia, with the production of microbial storage compounds such as polyhydroxylkanoates, by (i) subjecting the wastewater storage compound-accumulating microorganisms (SCAM) in the presence of oxygen, (ii) subjecting at least part of the resulting partly treated wastewater to ammonia-oxidising microorganisms (AOM) in the presence of oxygen and (iii) feeding a gas containing molecular carbon dioxide produced during step (ii) to step (i) so as to lower the pH in step (i).

Wastewater with high ammonia concentration is pre-treated before discharging it into a wastewater treatment plant treating lower strength wastewater, for example an activated sludge plant treating municipal sewage. The high strength wastewater is pre-treated to oxidize ammonia by contact with a fixed film supported on gas transfer membranes in a membrane aerated biofilm reactor. The pre-treatment may be a batch or continuous process. The pre-treatment can be controlled to remove ammonia to about the point of material alkalinity depletion. One or more parameters such as alkalinity, pH, or membrane exhaust oxygen concentration can be monitored to determine if alkalinity depletion has occurred or is about to occur. In some examples, the high strength wastewater is blended with wastewater having less ammonia and more alkalinity, for example municipal sewage or primary effluent. In some examples, the high strength wastewater is a liquid fraction of one or more sludges.

The present invention provides a nitrogen treatment method which can suppress the production of nitrate nitrogen to stabilize the concentration of nitrite nitrogen in a nitritation treatment in which ammoniacal nitrogen is biologically oxidized to produce the nitrite nitrogen. A nitrogen treatment method includes a nitrification treatment step of producing nitrite nitrogen by oxidizing ammoniacal nitrogen contained in water to be treated, using microbial sludge, wherein: a volume load of the ammoniacal nitrogen in the nitrification treatment step is set to a high load of 0.3 kg-N/m.sup.3.Math.day or more and 5 kg-N/m.sup.3.Math.day or less; and in the nitrification treatment step, at least one of a treatment of adjusting a pH of the water to be treated to pH 8 or more and pH 10 or less and a treatment of applying an inactivating operation for sterilizing microorganisms or causing bacteriostasis to the microbial sludge is performed.

Disclosed is a bioreactor for treating sewage comprising an aerobic tank including a mixing cell for receiving sewage to be supplied from an inlet and mixing the sewage with activated sludge and an aerobic reactor tank in which the activated sludge adsorbs organic substance existing in the sewage; a backwashing cartridge filter for removing floc resulting from growth of the activated sludge adsorbing the organic substance; and an anaerobic tank for carrying out a denitrification process for denitrifying treated water flowed through the backwashing cartridge filter using anaerobic ammonium oxidation (anammox) bacteria wherein the backwashing cartridge filter allows the sewage discharged from the aerobic tank to pass through the cartridge filter and separates the floc and the treated water using difference in size between the floc contained in the sewage and pores in the cartridge filter, and wherein foreign matter adsorbed on the cartridge filter is easily removed by means of washing water to be injected into the cartridge filter.

A system for mixing and mixing processes and structures are disclosed. In addition a nozzle used for mixing is disclosed.

Described is a method of treating wastewater. The method includes receiving the wastewater at a ballasted activated sludge secondary treatment aeration basin. The method also includes adding a ballast material to the wastewater, treating the wastewater in the ballasted activated sludge secondary treatment aeration basin to produce a ballasted mixed liquor effluent, receiving the ballasted mixed liquor effluent at a high-rate heavy solids removal zone that includes one or more high-rate heavy solids removal units, and removing ballasted heavy solids from the ballasted mixed liquor effluent using the one or more high-rate heavy solids removal units to produce a concentrated ballasted heavy solids effluent and a clarified liquid effluent. Also described is a system for treating wastewater including a ballasted activated sludge secondary treatment aeration basin and a high-rate heavy solids removal zone for treating a ballasted mixed liquor effluent.

Methods and systems for controlling a denitrification reaction in a biological nitrogen removal reactor including denitrifying bacteria to favor denitratation of nitrate to nitrite and limit denitritation of nitrite to nitrogen gas are disclosed. pH, dissolved oxygen levels, solids retention time, and chemical oxygen demand to nitrogen ratio are controlled to favor this reaction. Wastewater or contaminated groundwater including concentrations of ammonium and nitrate are continuously fed to the biological nitrogen removal reactor along with a source of carbon and electrons as an influent, which is treated to form a nitrite effluent. The nitrite effluent may then be fed to an anammox reactor including anammox bacteria for production of nitrogen gas. The system may be operated under substantially anoxic conditions, which provides significant cost savings without sacrificing efficiency or productivity compared to traditional wastewater treatment systems and processes.

[Problem] A carrier for retaining anammox bacteria, an anammox bacteria-adhered particle, and a wastewater treatment apparatus are provided that can remarkably reduce the start-up period for obtaining a nitrogen removal speed of 1 kg-N/m.sup.3/day.

[Solution] A carrier for retaining anammox bacteria includes carbon particles. The carbon particles are desirably graphite particles, particularly isotropic graphite particles. The carbon particles desirably have a zeta potential of 35 mV to 0 mV and an average particle size of 2 m to 1000 m.

A water treatment apparatus for removing nitrogen in raw water and a water treatment method using the same are provided. The water treatment apparatus includes a denitrification reactor configured to remove nitrogen contained in raw water supplied thereto, a phosphorus treatment tank configured to remove phosphorus (P) contained in the raw water supplied from the denitrification reactor, an anammox reactor configured to remove nitrogen contained in the raw water supplied from the phosphorus treatment tank through an anammox reaction, a partial nitritation tank configured to convert ammonium ions (NH.sub.4.sup.+) remaining untreated in the anammox reaction into nitrite ions (NO.sub.2.sup.), and a sedimentation tank configured to cause settling of suspended matter contained in the raw water supplied from the partial nitritation tank so that sludge forms and discharge the raw water through a raw water discharge pipe.

Provided is a process comprising receiving overflow of wastewater influent from a clarifier basin in a clarifier effluent collection trough; receiving inflow of wastewater influent from the clarifier effluent collection trough in a filter influent flow inlet distribution channel; maintaining substantially constant liquid level in the filter influent inlet distribution channel; applying hydrostatic pressure to push wastewater influent from the filter influent flow inlet distribution channel into an upflow backwash filter contusing denitrifying biomass or deammonification biomass; backwashing the backwash filter with a gas lift backwash flow; returning filter reject backwash wastewater from rejection compartment of the filter through denitrifying bacteria or deammonification biomass recycle return line to a location upstream of the filter; and recycling denitrifying bacteria or deammonification biomass from denitrifying bacteria or deammonification biomass recycle return line to at least one of the clarifier effluent collection trough, filter influent flocculation tank, or filter influent flow distribution channel.