Engineering & Quality Control Specialist Report（I）

Glen T. Daigger

1. Introduction

1.1 Background

CPR/96/302 (21st Century Urban Water Management in China) will assist the Ministry of Construction in launching a National Program for Sustainable Urban Water Management in China and in developing key institutional capacity to implement it. The overall program objective is to improve water and wastewater management by developing and demonstrating an effective process for institutional reform and implementation of a water demand management strategy. To assist in the design of the national program, the project will support pilot activities in the Municipality of Shijiazhuang, Hebei Province to determine the most appropriate methodology for implementing institutional and organizational reforms at the municipal level in China. An institutional reform strategy and an action plan for a revised tariff structure will be developed and implemented to establish fully self-financing water supply and wastewater companies in Shijiazhuang. Lastly, a program of training and technical support to disseminate the main findings of the pilot activities and launch the national program in additional cities will be tested.

This US $1.225 million project is financed by the United Nations Development Project (UNDP), with cost sharing by AusAID and the Municipality of Shijiazhuang. The Executing Agency is the China International Center for Economic and Technical Exchanges (CICETE). National program implementation will be led by the Ministry of Construction (MOC), and pilot implementation will be carried out under the Municipal Government of Shijiazhuang (MGS).

1.2 Scope

Dr. Glen T. Daigger, Ph.D., P.E., DEE, who is a Senior Vice President with CH2M HILL, was selected to serve as the Engineering & Quality Control Strategy Specialist for the project. The Terms of Reference (TOR) for the Engineering & Quality Control Specialist is as follows:

1 Introduce relevant international experience, best practices and technical aspects in regulations, license and qualifications on urban wastewater and water service;
2 Provide information and advice for establishing a national technical supporting system for evaluation and assessment of wastewater and water engineering projects and management;

3 Provide quality control and decision making procedures and strategy for the design, construction and operation of urban wastewater treatment projects, with special consideration on technical standards, processes selection, and biding and tendering;
4 Develop an integrated informative technical documentation on wastewater treatment technologies and practices suitable for China, primarily targeting on process and engineering services;
5 Develop a strategy of private sector or other sector involvement in water and wastewater services;
6 Attend a workshop in Beijing on September 14 - 17, 1999;
7 Submit a report on the topics listed above on or before August 25, 1999; and
8 Prepare presentation materials for the workshop.

This report was authored by the Engineering & Quality Control Strategy Specialist (Dr. Glen T. Daigger, Ph.D., P.E., DEE). It is submitted in conformance with TOR element number seven, listed above. It addresses TOR elements one through five. The report is provided in six sections, beginning with this introduction section and followed by five additional sections addressing the first five TOR elements listed above.

2. Regulations, License and Qualifications on Urban Wastewater and Water Service

2.1 Introduction

This section addresses TOR element number one for the Engineering & Quality Control Strategy Specialist. This element is to introduce relevant international experience, best practices and technical aspects in regulations, license and qualifications on urban wastewater and water service. Two general approaches are used to license and regulate wastewater and water service in urban areas:

1. Best Practices.
2. Performance Standards.

Each approach offers advantages and disadvantages and is appropriate for specific applications. These two approaches are described and compared below.

2.2 Best Practices

2.2.1 Description of Approach

The specification and enforcement of best practices is frequently used in many human endeavors, including urban wastewater and water systems. The facilities to be constructed, the methods of construction, and the operation and maintenance procedures to be used are specified in detail. The party responsible to implement the system is told what to do. Strict adherence to the specified procedures is generally mandated, and little is left to the judgment of those implementing the system. The result is relatively uniform conformance with the specified standard. Best practices are frequently specified in design manuals, codes, administrative rules, laws, and standard specifications. They encompass items such as the type of technology to be used, design criteria and procedures, materials of construction, construction methods, and operating procedures. Examples include codes for the design and construction of water distribution and wastewater collection systems, design standards for water and wastewater treatment facilities, standard specifications used by design professionals, and laws mandating the type of treatment technology that must be installed for particular situations.

Best practices are typically established by professional organizations and governmental agencies. A group of qualified practitioners describes the practice in sufficient detail that the intended result can be duplicated. Areas requiring professional judgment or local knowledge are also described.

2.2.2 Evaluation of Approach

The best practices approach offers advantages and disadvantages, as summarized in Table 2-1. Advantages include consistency, ease of implementation, and reduced reliance on experienced professionals. Disadvantages include increased cost, resistance to change, difficulty in adapting to new situations, and poor performance.

Table 2-1.Advantages and Disadvantages of Best Practices Approach. Advantages Disadvantages

Consistency. The essential elements of each system will be nearly identical and, consequently, will achieve the same level of performance.

Ease of Implementation. Since the nature of the system and the steps needed to implement it are well known, the requirements to implement it are also well known.

Reduced Reliance on Experienced Professionals. Since many of the details of the system are specified, the need for experienced professionals to determine those details is greatly reduced. Thus, an acceptable system can be implemented by less experienced professionals.

Increased Cost. Standard approaches must incorporate a degree of conservatism to accommodate the range of actual situations that might be encountered. But, in many instances that degree of conservatism may not be needed, leading to a facility or solution that is more expensive that actually required.

Resistance to Change. Strict enforcement of best practices discourages innovations that can lead to lower cost or higher performance options. This occurs because the existence of standards can make it difficult for innovations to be tried and tested in real life situations. Moreover, the existence of standards reduces the incentives to experiment with innovations.

Difficulty in Adapting to New Situations. When practicing professionals rely almost entirely on standard solutions, they will not possess the knowledge and experience required to identify a new situation where the specified best practice is not appropriate. Thus, when a unique or novel situation presents itself, it is likely that the solution initially applied will be inappropriate and may, in fact, fail to perform adequately.

Poor Performance. With this approach actions, rather than results, are specified. This, if the intended performance is not achieved, limited incentives exist for system implementers to change the approach to achieve a better result. System implementers have done what they were instructed to do and have, thereby, satisfied their duties.

The advantages and disadvantages for the best practices approach results in its application to specific situations. In fact, specification of best practices is necessary to allow timely and efficient implementation of urban wastewater and water systems. It is not possible, nor prudent, to develop unique solutions to each problem. The use of best practices is appropriate when:

- The problem to be solved is well understood and extensive experience exists supporting the effectiveness and efficiency of the best practice.
- Solutions must be implemented quickly. Time does not exist to evaluate and select from a wide range of alternatives.
- Consistency is needed to simplify monitoring of compliance and system operation and maintenance (O&M) requirements.
- The increased cost of more conservative approaches is small compared to the cost savings achieved by the use of consistent, easily implemented approaches.

2.3 Performance Standards

2.3.1 Description of Approach

In contrast with the best practice approach where the actions required by the party responsible for system implementation are specified, for the performance standards approach the results that must be achieved are specified. The implementing party is allowed to select an appropriate solution from a variety of options, as long as they comply with the specified performance standards. An example of the use of this approach is specification of the effluent quality that must be achieved by a wastewater or water treatment facility. The process selected must be consistent with the known constraints imposed by the laws of physics, chemistry, and biology. But, consistent with this constraint, any process can be selected and implemented as long as the resulting effluent complies with the specified standards.

2.3.2 Evaluation of Approach

The performance standards approach offers advantages and disadvantages, as summarized in Table 2-1. Advantages include efficient, lower cost, solution; greater assurance of performance; encourages innovation; and adaptable to changing situation. Disadvantages include slower project evaluation and acceptance, lack of uniformity, increased potential for project failure.

Performance based approaches are also applicable to the solution of urban wastewater and water problems. The are appropriate when:

- Significant potential exists to reduce system cost. In many instances, the "standard" or "typical" answer to a particular problem is relatively expensive and alternatives exist that can solve the problem much less expensively. However, site-specific issues dictate the applicability of these alternative solutions. Specifying performance allows these alternative solutions to be thoroughly investigated and the most beneficial one for a particular application to be selected.
- Operation and maintenance requirements are high. Best practices work well when the solution to a particular problem is largely structural in nature. In this case the required solution is put in place, but only limited on-going operation and maintenance is needed to allow the solution to continue to perform. It is difficult, however, to specify, and enforce, operation and maintenance procedures. When performance is specified and measured, the operating agency must provide the required operation and maintenance to ensure that the system installed will continue to perform. Thus, greater potential exists that the necessary operation and maintenance resources will be provided to ensure adequate system performance.
- The "standard" solution is no longer appropriate due to changing needs and expectation.

Table 2-2.Advantages and Disadvantages of Performance Standards Approach. Advantages Disadvantages

Efficient, Lower Cost, Solutions. Because site-specific solutions can be developed for each application, the resulting solution can be significantly more cost-effective than a “standard” or “generic” solution specified in a set of design standards. This arises because local situations can be highly variable, allowing for site-specific solutions that can, in many instances, achieve necessary performance at significantly reduced cost.

Greater Assurance of Performance. Because the implementing party is responsible for performance, rather than just a set of actions, enforcement action can be taken more directly if the resulting system fails to perform as specified.

Encourages Innovation. This approach can encourage innovation because it allows options with improved performance characteristics (lower cost, improved operability) to be implemented more rapidly. Adaptable to Changing Situations.
Because performance, rather than actions, is specified, actions must be changed when the situation changes to allow the system to continue to comply with the performance requirements.

Slower Project Evaluation and Acceptance. It is generally prudent to examine each project before it is implemented to ensure that it is consistent with known scientific and engineering principles and to develop some level of confidence that it possesses the capability to achieve the intended performance. The level of review to achieve this on individual projects is greater than in the previous case since a detailed technical review must be conducted on each project. In fact, if significant investments in urban wastewater and water facilities are required, the availability of trained and experienced professionals may limit the use of this approach

Lack of Uniformity. Because a great diversity of solutions may be used to solve the same problem, significant differences may arise between parallel systems intended to solve the same problem. This diversity may increase long-term operation and maintenance costs. Increased Potential for Project Failure.
Increased innovation will also increase the risk of failure for individual projects.

Greater Assurance of Performance. Because the implementing party is responsible for performance, rather than just a set of actions, enforcement action can be taken more directly if the resulting system fails to perform as specified.

Encourages Innovation. This approach can encourage innovation because it allows options with improved performance characteristics (lower cost, improved operability) to be implemented more rapidly.

Adaptable to Changing Situations. Because performance, rather than actions, is specified, actions must be changed when the situation changes to allow the system to continue to comply with the performance requirements. Slower Project Evaluation and Acceptance. It is generally prudent to examine each project before it is implemented to ensure that it is consistent with known scientific and engineering principles and to develop some level of confidence that it possesses the capability to achieve the intended performance. The level of review to achieve this on individual projects is greater than in the previous case since a detailed technical review must be conducted on each project. In fact, if significant investments in urban wastewater and water facilities are required, the availability of trained and experienced professionals may limit the use of this approach

Lack of Uniformity. Because a great diversity of solutions may be used to solve the same problem, significant differences may arise between parallel systems intended to solve the same problem. This diversity may increase long-term operation and maintenance costs.

Increased Potential for Project Failure. Increased innovation will also increase the risk of failure for individual projects.

2.4 Enforcement

Once system requirements are specified (either best practices or performance requirements), the method to ensure compliance must be specified. This requires monitoring. Two approaches are available here:

1. External monitoring.
2. Self monitoring.

External monitoring is performed by an organization external to the organization implementing the environmental solution. This is typically a governmental body, such as a regulatory agency, but it can also be a non-governmental organization such as a certification board. For best practice solutions, the enforcement organization inspects to determine whether the best practices have been implemented. For performance based solutions, the enforcement organization evaluates system performance to determine compliance with performance requirements.

For self monitoring approaches, the party responsible for implementing the environmental solutions also determines its performance and reports it to a regulatory body. This approach can apply to either best practice or performance based solutions. For best practice solutions the implementing body compares the system they have implemented with the specified best practices and "certifies" that it complies with those best practice requirements. For performance based solutions the implementing organization determines system performance and reports it.

2.5 Analysis

Most license, regulation, and qualification systems include a mixture of best practice and performance based standards. The use of performance based approaches is not practical for routine applications. Rather, the system to be installed is specified in a set of codes or regulations, and it is simply installed as specified. The development of unique solutions for each application is not cost-effective due to the time and expense required to develop such a solution. The added cost to develop the unique solution exceeds the potential cost savings that such a solutions can produce. Good examples of where best practice solutions can be productively applied is for the installation of water distribution systems and wastewater collection systems.

The system should also include the flexibility to develop unique solutions when the standard solution is not applicable and/or its application will lead to excessive costs. For example, when unusual soil conditions are encountered the development of a site-specific approach to installing water distribution and wastewater collection systems may be justified based on a reduction in overall costs. The development of site-specific, performance-based solutions for water and wastewater treatment facilities is also generally justified based on the overall cost savings achievable.

A good license, regulation, and qualification system will generally specify the generally accepted best practice; the performance expected from it; and procedures for developing alternative, performance-based solutions. This provides the flexibility, in any situation, to either implement the accepted best practice or to develop alternative solutions. If the accepted best practice appears reasonable and to result in an acceptable cost, it can be implemented. If, on the other hand, alternative solutions appear to offer significant benefits, they can be investigated and implemented using the performance based provisions of the regulations. In fact, experience with such alternative solutions may result in the development of new best practices that can be incorporated into subsequent regulations.

A good license, regulation, and qualification system will also generally incorporate both external and self monitoring provisions. A certain amount of external monitoring is generally required to ensure system integrity. However, it is not generally possible for external agencies to monitor all aspects of the installation, operation, and maintenance of urban wastewater and water systems. The system owner must take significant responsibility for the operation and maintenance of the system, and report the results. The owner may also report on many elements of system installation, for example by certifying to the external governmental agency that the system has been installed according to the specified best practices. In fact, it is generally not a good idea for the same agency to be totally responsible for regulations and for the installation, operation, and maintenance of the system. Such situations exist around the world, and they ultimately lead to systems that do not fully protect the environment and public health.

Experience suggests that self monitoring of operation and maintenance intensive systems, such as water and wastewater treatment facilities is effective. The system operator is in the position to collect performance information at a sufficient frequency to accurately monitor system performance. External regulatory agencies are generally not in a position to do this efficiently. However, to be effective the submission of false and/or misleading information must be treated as a serious offense that is quickly and severely punished. In fact, the submission of false and/or misleading information is often treated as a more severe offense that failing to comply with system performance requirements. Under these circumstances self monitoring systems are effective and possess high credibility.

3. National Support System for Project Evaluation and Assessment

3.1 Introduction

This section addresses TOR element number two for the Engineering & Quality Control Strategy Specialist. This element is to provide information and advice for establishing a national technical supporting system for evaluation and assessment of wastewater and water engineering projects and management. This element is related directly to the first TOR element, discussed in the previous section. The nature of the license, regulation, and qualification system affects the nature of the national support system. For the purposes of this discussion, it will be assumed that:

- A system exists that specifies performance requirements for urban wastewater and water systems, best practices for achieving this performance, and provides procedures to consider and adopt alternatives when they are found to be beneficial.
- A regulatory agency exists that is responsible to ensure that systems to meet the specified performance requirements, such as identified the best practices, are used when urban wastewater and water systems are implemented. It also ensures that performance requirements are satisfied.
- The regulatory agency uses a mixture of self monitoring and external monitoring approaches to ensure compliance with the specified performance requirements.
- A system owner exists that is responsible for implementation of the system and for its on-going operation and maintenance.

3.2 System Description

For the situation described above, the principal roles of a national technical supporting system for evaluation and assessment of wastewater and water engineering projects and management would be as listed in Table 3-1. Roles are listed in two categories:

1. Mandatory.
2. Optional.

Mandatory roles are those that are necessary to support the overall system listed above. They include the establishment of performance requirements and methods for achieving them, monitoring procedures, and project evaluation procedures. These mandatory roles provide the framework for implementing effective urban wastewater and water service infrastructure.

Optional roles provide added value and allow urban wastewater and water systems to be implemented more effectively and efficiently. They focus, particularly, on providing training and technology transfer to the local implementation agencies and to the organizations that serve them.
Table 3-1. National Technical Supporting System for Evaluation and Assessment of Wastewater and Water Engineering Projects and Management Roles. Mandatory Roles:

Establishment of performance requirements, best practices, and alternative evaluation procedures for urban wastewater and water systems.
Establishment of procedures for monitoring project conformance with best practice and performance requirements.
Establishment of procedures for evaluating alternative projects to determine whether they are likely to achieve performance requirements and should, therefore, is allowed to be implemented. Optional Roles:

Provide training in best practices and performance requirements.
Provide training in alternative evaluation procedures.
Provide technology transfer on new technologies that appear to be beneficial and potentially applicable to urban wastewater and water systems.
Provide education on project development and implementation.

A role that is not appropriate for this organization is the operation of urban wastewater and water systems. Conflicts inevitably arise when technical assistance and regulatory agencies also become operating agencies.

A national technical supporting system for evaluation and assessment of wastewater and water engineering projects and management would likely consist of four principal functional elements:

1. Policy.
2. Technical.
3. Regulatory.
4. Administrative.

Figure 3-1 illustrates these four principal functional elements of the national technical supporting system for evaluation and assessment of wastewater and water engineering projects and management. The policy element establishes the framework and scope for the system, as well as the procedures for interfacing with system implementers and operators. The technical element is responsible to establish technical requirements and to provide technical training. The regulatory element provides the means to ensure compliance with performance requirements. The administrative element is necessary to allow the organization to operate efficiently.

Figure 3-1. Functional Organization of National Support System for Evaluation and Assessment
of Wastewater and Water Engineering Projects and Management.

4. Quality Control and Decision Making Procedures and Strategy

4.1 Introduction

This section addresses TOR element number three for the Engineering & Quality Control Strategy Specialist. This element is to provide quality control and decision making procedures and strategy for the design, construction and operation of urban wastewater treatment projects, with special consideration on technical standards, processes selection, and biding and tendering. This TOR element will be addressed in the context of the project implementation approach described in Section 3.1, above. In that context, the system in place will provide the following:

- A national technical and regulatory agency that will define performance requirements for urban wastewater treatment projects, and the best practices that will allow those performance requirements to be met. This agency will also define procedures to allow alternative options to be evaluated for their potential ability to comply with the required performance standards.
- A separate agency (such as an element of local government) will be responsible to implement the wastewater treatment project, consistent with the procedures established by the national agency. This same local agency would be responsible for the operation and maintenance of the facility.

Three elements of project implementation will be addressed:

- Technical Standards.
- Process Selection.
- Bidding and Tendering.

4.2 Technical Standards

Technical standards play a crucial role in quality control and decision making procedures and strategy for the design, construction and operation of urban wastewater treatment projects. Technical standards are a necessary component of the system outlined immediately above, and described in previous sections of this report. As outlined there, an overall regulatory, license and qualification system for urban wastewater and water service will specify performance requirements, best practices for this performance, and procedures for assessing and selecting alternatives. An important element of the specified best practices will be technical standards.

Technical standards are available from a wide range of sources for the evaluation, selection, and design of urban wastewater project. These include professional organizations such as the Water Environment Federation (WEF), the International Association on Water Quality (IAWQ), the American Society of Civil Engineers (ASCE), and other national water pollution control associations; a wide variety of codes of practice and building codes; technical standards used formally and informally by various Federal and provincial water pollution control agencies; and technical standards used by professional organizations actively engaged in implementing urban wastewater systems. In general, these standards describe the characteristics of an acceptable system, and how to implement such a system. In short, they provide the definition of "best practice", as described in previous sections of this report. As such, they provide an excellent basis for accomplishing quality control.

Technical standards best serve two functions:

1. Define the technical details of best practices.
2. Describe the performance expected from best practices.

When the best practice is selected for implementation, technical standards provide much of the technical information required for successful implementation. As such, they provide a necessary basis for quality control for project implementation.

Because technical standards also define the performance expectations resulting from the implementation of best practice, they also provide the basis for evaluating alternative solutions. This is one necessary element for urban wastewater treatment projects. However, they will not generally provide the basis for decision making for urban wastewater treatment projects. This is because of the great diversity and variety of urban settings, resulting in the availability of a large number of technical solutions that could be successfully implemented. Selection of the best option for a particular application should be left to the local implementation agency, using the format described above. If unusual circumstances do not exist, and no significant financial incentives exist to select a different solution, then it might make the most sense to simply select the best practice options and implement it. However, the flexibility should be retained to select and implement alternative solutions when dictated by local conditions and/or when cost savings or other benefits can be achieved.

4.3 Process Selection

In the context of the previous discussion, one of the principal decisions is whether the "best practice" process should be selected and implemented, or whether an alternative process should be used. The selection of an alternative process should be based on the potential advantages associated with the alternative process. Assessment of the potential advantages provides the basis for evaluating and deciding between the best practice process, and the alternative process.

The availability of a "best practice" process for various applications facilitates decision-making. It provides a baseline for comparison of alternative processes to clearly identify advantages for alternative processes. Selection of an alternative process, then, is based on assessing the advantages (and disadvantages) of the alternative process, in comparison to the best practice. Table 4-1 summarizes questions that should be asked and answered in the course of evaluating alternative processes, in comparison to the best practice process.

If the benefits of the alternative process exceed the associated risks, then a basis exists for selecting it. If an alternative process is selected, then an implementation plan should be developed to maximize its chances for successful implementation. This plan should include:

- A clear, simple definition of the performance requirements for the process, and procedures for quantifying them.
- An analysis of risks associated with implementing the alternative process, and methods for mitigating these risks.
- A process for mitigating the risks associated with the alternative process.
Table 4-1 Questions to be Considered in Evaluating Alternatives to Best Practice Processes. What Advantages Does the Alternative Process Offer, in Comparison to the Best Practice Process?
What Disadvantages Does the Alternative Process Offer, in Comparison to the Best Practice Process?
How Can the Potential Benefits of the Alternative Process be Quantified so That They Can be Measured?
What are the Risks Associated with the Alternative Process, and How Can They be Mitigated?
Do the Benefits Associated with the Alternative Process Exceed the Risks?

4.4 Bidding and Tendering

Quality control in bidding and tendering is crucial to successfully implement urban wastewater treatment projects. In general, regulatory agencies and agencies responsible to oversee the implementation of urban wastewater treatment projects should ensure that an appropriate Quality Assurance/Quality Control (QA/QC) program is in place for the project. Quality Assurance is the specification of procedures to be used to ensure that the appropriate quality is achieved for the subject project. Many professional organizations have general QA programs that describe the typical procedures used on their projects. Oversight organizations may also wish to develop typical QA plans as a starting point for the implementing organization. Such general plans can then be made specific for a particular project.

Quality Control is implementation of the QA procedures on the subject project. The QA plan will generally describe the standards and guidelines to be used on the subject project, review procedures to be used, and how the results of the QC process will be documented. Oversight of the project would appropriately involve review of the QA plan, and oversight to ensure that QC has occurred.

5. Wastewater Treatment Technologies and Practices Suitable for China

5.1 Introduction

This section addresses TOR element number four for the Engineering & Quality Control Strategy Specialist. This element is to develop an integrated informative technical documentation on wastewater treatment technologies and practices suitable for China, primarily targeting on process and engineering services. Topics to be addressed in this review include:

- Overview of wastewater treatment objectives.
- Wastewater collection systems.
- Liquid Treatment Technologies.
- Solids Processing Technologies.

5.2 Overview of Wastewater Treatment Objectives

Before reviewing wastewater treatment technologies and practices suitable for China, it is helpful to define the requirements to be expected for such systems. Historically wastewater treatment systems have been used to protect public health through the removal of pathogenic organisms and to remove pollutants that cause obvious affects of wastewater discharges. The latter class of pollutants includes oxygen demand, generally as expressed by the five-day biochemical oxygen demand (BOD5), settleable solids, oil and grease, and floatable materials.

Increasingly, however, wastewater treatment systems are being required to remove other contaminants. This occurs because wastewater discharges are causing deterioration of receiving water quality. Especially for a water short country, such as China, adequate wastewater treatment is a necessity to preserve water quality and ensure that the available water can be used multiple times and for multiple purposes. Wastewater reclamation and reuse is also being increasingly practiced in water short areas to allow the available water supplies to meet the needs of human population. These needs define the requirements for wastewater treatment systems for the future.

The historical requirement for wastewater treatment facilities to remove BOD5 and total suspended solids (TSS) remains in effect. The removal of TSS will also result in the removal of other pollutants associated with wastewater, including floatables and oil and grease. These pollutants must be removed because they interfere with the normal use of the water when it is discharged. TSS (and the associated floatable and oil and grease) removal is relatively inexpensive. It is also a necessary prelude to, or a component of, the removal of other pollutants. BOD5 removal is also necessary for most discharge locations and/or uses of the effluent. However, other treatment requirements will increasingly control process wastewater treatment process selection because they will determine treatment requirements, not BOD5.

Nutrient control is increasingly required to protect the quality of a number of receiving waters. Discharges to fresh water generally require phosphorus removal to control the growth of excessive quantities of algae and other aquatic organisms. Nitrogen removal is not generally required to protect fresh water receiving water quality, but nitrification is generally required to reduce oxygen demand. However, nitrogen removal will be required to protect surface water for subsequent use as a water supply. Some degree of nitrogen removal (i.e. denitrification) is often cost-effective when nitrification is required. Note that implementation of nitrification will generally dictate extensive removal of BOD5. Discharges to ground water will also require nitrogen removal to protect its future use as a water supply. In coastal areas both phosphorus and nitrogen removal is required to protect ( restore) water quality in estuaries. In short, the question that should be asked is what level of nutrient removal is required to protect water quality, not whether nutrient removal will be required.

Toxic compounds must also be removed from wastewater to protect subsequent use. In general, the best strategy is to not discharge the toxicant in the first place. This is because wastewater treatment processes are not generally very effective in removing trace contaminants, especially when the treatment system must serve as a consistently performing barrier for such contaminants. However, maximizing the toxicant removal of a wastewater treatment process is beneficial to protect the future uses of the receiving waters.

A final requirement is disinfection. Disinfection is a historical requirement of wastewater treatment systems, as it is the foundation of the public health purpose for these systems. Disinfection has historically focused on indicators of bacterial pathogens, i.e. fecal coliforms, and human parasites. Increasingly, however, concern is focusing on other pathogens such as viruses and protozoa such as Cryptosporidium and Giardia. Wastewater treatment disinfection systems still tend to focus on historical disinfection requirements. However, water reclamation and reuse systems are increasingly concerned about the emerging pathogens that are also a focus of modern water treatment practice. Control of these pathogenic agents will focus on the control of particulates, along with disinfection practices. It is reasonable to think that, in time, some of the requirements being applied to potable water systems will also be applied to wastewater treatment systems. This means that the particulates in wastewater treatment plant effluents will be a concern.

5.3 Wastewater Collection Systems

Historically the collection and conveyance of stormwater drainage and the collection of wastewater have been inter-tied. In fact, stormwater and wastewater collection systems are often one in the same. In the past, when wastewater treatment requirements were much less stringent, the treatment of significant quantities of stormwater (and groundwater) along with wastewater was a reasonable approach. However, with the more stringent effluent quality requirements now placed on wastewater treatment plants, the treatment of large quantities of dilute wastewater significantly increase wastewater treatment costs and affect the technologies that are used.

Different approaches and technologies can be used that more completely separate wastewater from extraneous, clean water flows. Such technologies are being developed and have received some full-scale applications. In particular, the development of smaller diameter, shallow sewage collection systems constructed from PVC pipe offers the potential for more efficient collection of sewage while excluding clean water. Such systems, also referred to as condominial sewerage, have been used successfully in several locations. A good description of them is provided by Mara, 1996. Experience indicates that sources of extraneous water flow into the major interceptors of conventional wastewater can be corrected. However, extraneous water flows from private connections are very difficult to exclude from conventional systems. Condominial systems, such as those described by Mara, make it more difficult for private houses to connect their drainage systems to the wastewater collection system. Consequently, they are much more effective in excluding extraneous water flows. The use of PVC pipe for these systems also results in a system that is more "water tight" and able to exclude extraneous flows.

Separation of the wastewater collection and the stormwater (and in some cases groundwater) collection systems requires that an effective stormwater collection system be provided. Without it, the temptation to connect surface drainage to the wastewater collection system to alleviate flooding is too great.

Exclusion of extraneous water flows from the wastewater collection system can significantly reduce the wastewater flow rate, which reduces wastewater treatment costs. The strength of the wastewater is also significantly increased, which makes new liquid treatment technologies technically feasible, as discussed in the next section. It will also increase the temperature of the wastewater (since stormwater and groundwater is often of lower temperature than wastewater), which will also make the application of new technologies more feasible.

5.4 Liquid Treatment Technologies

Many wastewater treatment technologies are available and applicable to the situation in China. This section will review some of the newer, developing technologies that might find particular application to China in coming years. Topics to be addressed include:

- Pond Treatment Systems.
- Advanced Primary Treatment.
- Biological Nutrient Removal.
- Disinfection.
- Anaerobic Treatment.
- Membranes.

5.4.1 Pond Treatment Systems

Pond systems of various types have been used for centuries (even millennia) to treat municipal wastewater. They have proven quite effective in protecting public health as pathogens are effectively destroyed in appropriately designed pond systems. However, they require relatively large amounts of land, and they have not been capable of producing an effluent quality that protects the quality of receiving waters. Thus, their use has declined in the developing and the developed world.

Interestingly, over the past few years a new generation of pond wastewater treatment technologies has been developed that is more efficient and is capable of producing a higher quality effluent. Some particularly interesting new systems include:

- Dual-Power Multicellular (DPMC) Aerated Lagoons.
- Advanced Integrated Pond Systems (AIPS).
- Pond Enhanced Treatment and Optimization (PETRO)

These systems are described below.

5.4.1.1 Dual-Power Multicellular Aerated Lagoons

In a conventional lagoon wastewater treatment system, algae provide the oxygen required to biodegrade the organic matter contained in the influent wastewater. An alternative is to use mechanical means to provide the necessary oxygen. In dual-power multicellular (DPMC) aerated lagoons, mechanical aerators provide the oxygen needed to biodegrade the influent organics. In addition, they are designed specifically to minimize the growth of algae that can pass into and deteriorate the quality of the effluent.

A DPMC lagoon system consists of two lagoons in series, each designed to provide specific functions (Rich, 1999; Grady, Daigger, and Lim, 1998; Rich, 1982a,b,c). The first lagoon is completely mixed and is designed to biodegrade the organics contained in the influent wastewater and convert them to biomass. The second lagoon is used to settle and store the synthesized biomass. Figure 5-1 presents a schematic of the process, illustrating the functions of each lagoon.

Figure 5-1 Dual Power Multicellular (DPMC) Aerated Lagoon.

The HRT (which is also equivalent to the SRT in a completely mixed lagoon) in the first lagoon is typically about 2 days. This usually is sufficient to biodegrade the influent wastewater organics and produce effluent soluble BOD5 concentrations less than 10 mg/l. Sufficient mixing energy is also provided to maintain biological solids in suspension (generally about 10 W/m3, or 50 Hp/MG). The turbidity provided by the suspended biomass limits light penetration into the lagoon, which prevents algae from growing.

The HRT in the second lagoon usually ranges from 3 to 4 days. Mechanical aeration also is provided in this cell, but the power density is insufficient to maintain biological solids in suspension. This allows the biological solids synthesized in the upstream completely mixed lagoon to settle. Suspended solids, which are either present in the influent wastewater or synthesized in the upstream completely mixed lagoon, are stabilized anaerobically in the sludge layer. Anaerobic processes in the sludge layer result in the production of reduced products, such as methane, hydrogen sulfide, and reduced organic compounds, which diffuse into the overlying clear water layer. Oxygen present in this layer results in oxidation of the hydrogen sulfide and reduced organic compounds and control of odor emissions from the lagoon. Aeration of the overlying water layer provides the oxygen required to oxidize these reduced compounds, as well as to further oxidize soluble organics contained in the effluent from the first lagoon. Aeration also provides mixing energy, which mixes the overlying clear water layer. Algae growth in the second lagoon is controlled by controlling the HRT in the clear water zone to between 1 and 2 days. This is accomplished by dividing the second lagoon into a cells-in-series configuration using membrane curtains or by separating it into individual cells.

The DPMC aerated lagoon offers a simple and effective wastewater treatment alternative for smaller wastewater treatment plants. More recently Rich has developed approaches to allow these systems to be upgraded to provide nitrification and nutrient removal (Rich, 1999).