Thermal sludge conditioning liquor was successfully treated by a pilot‐scale upflow anaerobic hybrid system with an effective volume of 10.4 m3. The reactor was similar to the HYAN reactor in Lakeview but without a recirculation system. A gas‐solid separator was installed above a filter packed with polypropylene pall rings. The organic loading rate was increased stepwise to 30 kg chemical oxygen demand (COD)/m3 · d. The hydraulic retention time was only 6 hours at the target loading rate.
More than 70% of soluble COD in the influent was removed, even at an organic loading as high as 30 kg COD/m3 · d. Soluble 5‐day biochemical oxygen demand (BOD5) removal efficiency at the loading rate exceeded 95%. Volatile fatty acids concentration in the effluent was consistently less than 60 mg/L after the day when stable treatment had been obtained. The methane production fluctuated between 0.3 and 0.4 L/g COD removed. Solids production including effluent suspended solids (SS) was between 0.16 and 0.24 kg SS/kg COD removed.
The inside of the reactor consisted of two zones, a sludge blanket zone with less than 1% solids concentration and a sludge bed zone with 47% solids concentration. Although the reactor was seeded with an anaerobically digested sludge, granular sludge was produced in the reactor. The ratio of granules to the solids remaining in the reactor increased to approximately 70% at the end of the experiments. Most of the granules had diameters of less than 1 mm and their settling velocity was 0.6 cm/s or more. The granules were composed of bacteria like Methanothrix according to SEM observations. The methane production rate was between 0.8 and 1.1 kg methane as COD/kg SS · d in an acetate solution.
According to substrates distribution in the reactor and tracer tests, the bed zone in the reactor worked similarly to a continuously stirred tank reactor (CSTR). Evaluation of soluble COD removal rates in the reactor indicated that the rate could be simulated by a Monod type reaction.

Thermal sludge conditioning liquor from a municipal wastewater treatment plant was successfully treated with a pilot-scale upflow anaerobic hybrid reactor with an effective volume of 10.4 cu.m. More than 70% of soluble COD in the influent was removed even at an organic loading as high as 30 kgCOD/cu.m/day. Though the reactor was seeded with an anaerobically digested sludge, granular sludge was produced in the reactor. The ratio of granular sludge to the solids in the reactor increased up to about 70% at the end of experiment. Biological activity of the granular sludge was measured as a methane producing rate using an acetate solution. Physical characteristics of the sludge, such as diameter distribution, composition and settling velocity, were also measured. It was found through tracer tests using lithium chloride that the reactor worked as a CSTR.

Sludge melting systems have been recently applied to the treatment of a great deal of sludge generated from sewage treatment plants, and the plant scale has become bigger and bigger in accordance with the social requirements. This paper reports operating data of one of the biggest scale melting plants for sewage sludge equipped with two reflector type melting furnace trains and includes running cost data as well as estimates for scaling up the process.

The circulated aeration type biological denitrification system, named the Kubota Nitro-cycle System, has been developed for removing total nitrogen in night soil. It has the following features:In the circulated aeration tank, BOD removal, nitrification and denitrification can be simultaneously conducted by activated sludge treatment without dividing the tank into an aerobic zone and an anaerobic zone, and it is possible to remove 80–90% of the total nitrogen and BOD in night soil influent.Denitrification and re-aeration tanks are provided after the circulated aeration tank and over 99% removal of total nitrogen and BOD can be attained with the whole system.In this system, not only nitrogen, but also phosphorus can be removed to the extent that there remains only a trace and this is effective to prevent eutrophication.This system was approved by the Ministry of Health and Welfare of the Japanese Government in 1978 as a new technology for night soil treatment.

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