Advanced Phosphorus Removal and Needs for Recovery by Enhanced Filtration of Municipal Wastewater

The need for an advanced and even far reaching phosphorus removal at municipal WWTPs may soon get stipulations in relation to a reuse of phosphorus (P). This paper discusses the possible ways to remove phosphorous from municipal wastewater. This is already an established demand in many countries. However, as P is a limited raw material, this need for a reuse of P will become an example of what now is labelled “cyclic economy”. For instance, a national demand from the German state is already put in force. In this perspective the advanced filtration techniques will play an interesting role, and most possibly a crucial role. Examples are presented from several municipal WWTPs already in operation with a final polishing treatment step based on chemical precipitation and separation of phosphorus. Typical stable discharge P levels are found at these plants at levels < 0.05 to 0.10 ppm. The new demands on phosphorus recovery will also call for modified process concepts for the WWTP;for instance, a refined biological phosphorus removal (EBP) attains more attention and he needed very low discharge levels of P, where the enhanced P-removal will include different smart filtration techniques.

Problems in Water Environmental Control—Sense and Nonsense in Measurement of Water Protection

Water environmental control and process refinement inside a wastewater treatment plant (WWTP) is fundamentally based on sampling, analysis and on-line measurements on water and sludge streams. The problems related to an accurate and reliable control and thus an efficient water protection are addressed in the following. Four different crucial points whenever a sampling and control scheme is planned: 1) Where should a sampling and on-line measurement take place? 2) When should sampling take place? 3) How should the sampling and on-line measurement take place? 4) Which variables should be controlled? Examples are given from different plants demonstrating ways to address the questions. Especially the relevance of the adopted parameter BOD (Biochemical Oxygen Demand) is discussed. It is finally suggested to even abandon the use of BOD as consent variable in favor of on-line measurement of Suspended Solids, Nitrogen and Phosphorous.

Swedish Experience and Excellence in Wastewater Treatment Demonstrated Especially in Phosphorus Removal

Water quality protection in Sweden has a more than 80-year history. The needed knowledge has by large been imported. Now, to some extent the development of phosphorus removal technology may be Swedish contribution to advanced knowledge. This paper presents the development in Sweden, mainly a close to 50-year period. Starting in the late 1960s, a standard of <0.5 mg P/l was the normally raised effluent criteria, regardless of the magnitude of the discharge flow. The successive sharpening of the discharge levels has today resulted in a level of 0.2 to 0.3 mg P/l typically. As a matter of fact, even levels of 0.1 to 0.15 mg P/l have been discussed. The period should a large extent demonstrated both improved technologies and a far better efficiency with respect to the use of chemicals and energy. Some important points in this development may be the understanding of the Oxygen Consumption Potential, as well as the identified needs for an improved nitrogen removal. Lately the problems of complex pollution agents and predominantly the remains of pharmaceutical agents have been identified. To illustrate the development during the 50-year period, two examples are presented from the Swedish context. The main conclusion in this paper is that the Swedish history on phosphorus removal illustrates how empirical science in practice sometimes works, including a never-ending need for an open mind and a readiness to take revised and improved knowledge on board.

How Sustainable Is Our Wastewater Treatment?

The sanitation and environmental problems related to human activities can be traced at least around 2 500 years back, with written evidences both in the Old Testimony and the Greek culture. Thus in this perspective the matter is by convention an acknowledged problem since long. On the other hand our modern treatment systems of wastewater have far more recent roots. As an example, this year the very widespread biological treatment based on activated sludge celebrates it 100 year anniversary. In this perspective we may see a fundamental need to discuss and scrutinize the current systems in a “sustainable” perspective. A challenge for the technical society is to provide some “quantified” criteria on the concept sustainability. The wastewater treatment systems as we know them and develop them may be addressed by applying four major “sustainability” criteria: 1) The sustainability from major sanitation viewpoints;2) The sustainability from environmental viewpoints;3) The financial sustainability for the technical systems;(4) The sustainability with respect to adopting the systems into a more or less consistently changing society.

Why Should We Bother on Measurement in Wastewater Treatment Operation?

The question of wastewater treatment and control is reflected from a very specific viewpoint: the low priority given to accurate and useful measurements within wastewater treatment. The matter is discussed from four various perspectives, that may be labelled “Legal understanding”;“Needs for accurate measurement results already in the planning and design stage”;“The measurement problem and human behaviour”;“The understanding of the short term and long term dynamics and changes in pollution and flow loads on a wastewater treatment plant (WWTP)”. All these aspects bring about much improved needs for an accurate and frequent measurement scheme both for pollutants and flows entering a WWTP. The conclusion is stated as follows: A far more and well elaborated on-line measurement system at the plants would become a needed tool for improved water environment protection at lower costs.

Process Adaption and Modifications of a Nutrient Removing Wastewater Treatment Plant in Sri Lanka Operated at Low Loading Conditions

The Sri Lankan national water authority, that is The National Water Supply and Drainage Board (NWS&DB) has taken a new wastewater treatment plant into operation at Ja Ela, North of Colombo. The plant has been in operation since September 2011. In April 2012, it was concluded how a test of the aeration efficiency and a performance test should be carried out. The tests have been based on the actual loading of the plant and the analysis results from the daily process control. The evaluation of the aeration efficiency is not reported in this paper. The paper presents the overall performance of the water treatment part of the plant during start-up conditions, from fall 2011 through the first five months of 2012. The results from the operation are found in Table 1. An important circumstance at the plant is the current very low loading in comparison with the design load. This fact has resulted in an introduction of an intermittent mode of the aeration (nitrification) reactor. Based on operation figures, during more than a month (May 2012), it has been possible to give a realistic assessment of the overall performance. The most striking results are summarized as follows: 1) The intermittent operation has enabled an energy efficient operation of the plant. By the introduction of the intermittent aeration, the energy consumption has been reduced by around 75%, compared with the continuous operation mode;2) The plant performance during the intermittent operation has been improved with respect to virtually all important pollution variables. The most striking improvement is the discharge total P level, reflecting that a substantial enhanced biological phosphorus removal takes. The typical discharge levels found during May 2012, were compared with the earlier obtained values. It is important to underline that the loading on the plant has slightly increased during May as compared with the previous operation period.

Biological Removal of Nitrogen Compounds at a Coke-Oven Effluent Stream

The steel company SSAB in Oxel?sund, Sweden operates a coke-oven plant and has since a long time operated an activated sludge plant for treatment of effluent water. Along with more stringent requirements on discharge quality, especially focusing on nitrogen compounds and a new consent value for total nitrogen discharge (< 30 ppm of total N) the company decided to operate a pilot plant facility to investigate two major issues: 1) To define the conditions and restrictions for nitrification of ammonia nitrogen in the water;2) To find out how efficiently a denitrification would perform. In order to find answers to these questions SSAB hired a pilot plant for testing. The test facility is based on a single sludge activated sludge reactor system for biological nutrient removal, with a reactor volume of 3.8 m3. After a test period of 5 months it was possible to draw reliable conclusions regarding the performance. The untreated wastewater has a high content of total nitrogen, around 240 ppm. The major nitrogen part is ammonia nitrogen, but an important fraction is found as thiocyanate nitrogen. The following main conclusions were drawn from the test operation: · It was found to be crucial that the solids retention time (SRT) was kept at a sufficiently high level. During the successful operation the SRT was in the range of 40 - 50 days;· It is desirable to have an equalization basin upstream the main biological reactor to meet short time peak loads, defined as both flow and pollution;· The major toxic risks for the biological process were high thiocyanate and ammonia concentrations in the raw wastewater;· The system showed however a good microbiological capacity to acclimatize to the prevailing conditions after the needed time;· The tests did not include an optimization of the oxygen supply with respect to nitrification;however it was evident that the oxygen level was sufficient to maintain a complete nitrification at normal operating conditions;· Once the nitrification was established it was also possible to reach a high degree of denitrification—as long as an external carbon source was applied;· It was found that both the cyanide nitrogen and especially the thiocyanate nitrogen were reduced by the process. The cyanide reduction is probably related both to precipitation by ferrous ions and biological transformation.