Eikelboom to help with sludge training

Industry expert Professor Dick Eikelboom is to speak on a course organised by CIWEM and Leeds University. Microbiological assessment of activated sludge will be covered in detail.

Over the past decade the regulatory demands made of STWs have become increasingly strict. Prior to the creation of the NRA in 1989 most STW operators would have been content to achieve the Royal Commission’s 20/30 standard for biological and chemical oxygen demand (BOD and COD).

Nowadays in addition to achieving tighter consents for BOD and suspended solids removal on a 95 percentile basis, STWs are expected to achieve one or more of the following; nitrification, nitrogen or phosphorus removal, disinfection, colour removal, volatile organic carbon (VOC) or COD removal.

In addition, Environment Agency (EA) trials are underway to test the feasibility of using direct toxicity assessment (DTA) on both domestic and industrial treatment plant effluents. This will cause some plants major problems with compliance. As well as compliance, there are additional issues with sludge production and disposal, and odour elimination at all stages in the treatment train.

In order to tackle these operation and control issues, the role of staff training is increasingly important to ensure there is an adequate skills base within the workforce. In response to this need, Leeds University’s Aqua Enviro Technology Transfer, in collaboration with the Chartered Institution of Water and Environmental Management (CIWEM), has organised a two-day training event on the advanced design and operation of activated sludge systems.

How to stop bulking

The course will cover the activated sludge process from influent through to effluent and review the advances in our understanding that have led to current design and operating experiences. Starting off with process design aspects, it considers how the design brief has changed over the years and the design approaches now taken to achieve consent and minimise bulking.

This will be concluded by detailed guidelines on gathering information for flow and load values to apply in design. Increasingly contractors are requiring treatability studies prior to construction works, both to minimise the risks of potential settleability or toxicity problems, and to gather more reliable data to tighten up and optimise the final process design.

The applications of treatability testing will be outlined, with case studies to illustrate its usefulness in identifying potentially difficult wastewaters. Process control itself will be considered from the point of view of energy saving from aeration, as well as points in the process where control is best exerted.

The course will also offer a rare opportunity to hear Professor Dick Eikelboom speaking on process control by microscopic examination. Whenever activated sludges are microscopically examined, it is standard practice to identify filamentous bacteria based on the Eikelboom guidelines.

Prof Eikelboom is planning to provide a summary of his work on this subject over the past two decades. It will certainly be interesting to hear how the Netherlands has completely eliminated its sludgebulking problem. Throughout the world there has been a major research initiative aimed at understanding the causes of, and suggesting potential cures for, filamentous bulking and foaming.

Several scientists, including Prof Eikelboom, have questioned the identities of the common filamentous types observed in the UK (namely type O21N, Microthrix parvicella, Nocardia sp. and type 0041), suggesting that many more species are involved than revealed by morphological examination. Some authors have also observed that filaments can adopt more than one morphological characteristic, changing from, for instance, short rods to long filaments. These observations help to explain many of the contradictions in incidences of bulking where the same species is attributed to high and low loaded conditions, or appearing to like both oxic and anoxic conditions.

Although bulking has not yet been eliminated in the UK, it is certainly easier to control and handle by optimisation of the design and operation of solids removal systems and this will form part of a large session on bulking control.

The training course will also include a brief introduction to odour control. Some of the newer process modifications now being specified will be discussed along with the potential for advances in hybrid technologies and membrane systems.

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