Design of Water Reclamation System
/ By Panorama Consulting & Engineering Inc. / Sustainable Engineering • System design • Waste Reduction/ 0 Comments

Water reclamation systems design

Urban water reuse is a term generally applied to the use of reclaimed water for the beneficial irrigation of areas that are intended to be accessible to the public, such as golf courses, residential & commercial landscaping, parks, athletic fields, roadway medians, etc.

Expanded uses for reclaimed water may also include fire protection, aesthetic purposes (landscape impoundments and fountains), industrial uses and some agricultural irrigation.

Reclaimed water is domestic wastewater or a combination of domestic and industrial wastewater that has been treated to stringent effluent limitations such that the reclaimed water is suitable for use in areas of unrestricted public access. Since most areas where reclaimed water is to be used are designated for public access, protection of public health is the primary concern. Although utilization of reclaimed water will be beneficial, there is no guarantee that this source will provide all the water that is needed or desired.

Highly treated reclaimed water that meets the requirements of these guidelines is a valuable water resource. Wastewater treated to urban water reuse standards may be used in lieu of potable water for agricultural irrigation (feed crops), residential/commercial landscape irrigation, dust control, etc. The reclaimed water system is an integral part of the utility system and provides benefits to both the potable water and wastewater utilities.

Some of the substances that can be removed from wastewater include:

  • Suspended solids
  • Volatile organics
  • Semi-volatile organics
  • Oil and grease
  • Hydrocarbons
  • Metals
  • BOD
  • COD
  • Color
  • Odor
  • Hardness
  • Minerals

Reclamation processes:

Wastewater must pass through numerous systems before being returned to the environment. Here is a partial listing from one particular plant system:

  • Barscreens – Barscreens remove large solids that are sent into a grinder. All solids are then dumped into a sewer pipe at a Treatment Plant.
  • Primary Settling Tanks – Readily settable and floatable solids are removed from the wastewater. These solids are skimmed from the top and bottom of the tanks and sent to the Treatment Plant where it’ll be turned into fertilizer.
  • Biological Treatment – The wastewater is cleaned through a biological treatment method that uses microorganisms, bacteria which digest the sludge and reduce the nutrient content. Air bubbles up to keep the organisms suspended and to supply oxygen to the aerobic bacteria so they can metabolize the food, convert it to energy, CO2, and water, and reproduce more microorganisms. This helps to remove ammonia also through nitrification.
  • Secondary Settling Tanks – The force of the flow slows down as sewage enters these tanks, allowing the microorganisms to settle to the bottom. As they settle, other small particles suspended in the water are picked up, leaving behind clear wastewater. Some of the microorganisms that settle to the bottom are returned to the system to be used again.
  • Tertiary Treatment – Deep-bed, single-media, gravity sand filters receive water from the secondary basins and filter out the remaining solids. As this is the final process to remove solids, the water in these filters is almost completely clear.
  • Chlorine Contact Tanks – Three chlorine contact tanks disinfect the water to decrease the risks associated with discharging wastewater containing human pathogens. This step protects the quality of the waters that receive the wastewater discharge.

At various stages in the multistage treatment process, unwanted constituents are separated using

  • Vacuum or pressure filtration,
  • Centrifugation,
  • Membrane-based separation,
  • Distillation,
  • Carbon-based and zeolite-based adsorption, and
  • Advanced oxidation treatments.

Activated carbon is a highly adsorbent form of carbon that is produced when charcoal is heated. It removes impurities via adsorption from both aqueous and gaseous waste.

Membranes allow materials of a certain size or smaller to pass through but block the passage of larger materials. Imaginative arrays of membrane materials in innovative physical configurations are used to separate unwanted solids and dissolved chemicals from tainted water. During operation, purified water diffuses through the micro-porous membranes and collects on one side of the membrane, while impurities are captured and concentrated on the other side.

Today, membranes made from cellulose acetate, ceramics, and polymers are widely used. The applications come in a variety of innovative designs, including tubular, hollow-fiber, plate-and-frame, and spiral-wound configurations. The goals of membrane design are to

  • Maximize the available surface area,
  • Reduce membrane pore size (to allow for the more precise removal of smaller contaminants),
  • Minimize the pressure drop the fluid will experience when flowing through the unit, and
  • Identify more cost-effective system designs.

The addition of oxidizing agents—chemical ions that accept electrons—has proven effective against these microorganisms like waterborne viruses, bacteria, and intestinal protozoa. Today, a variety of advanced oxidation techniques kill such disease agents and disinfect water, thanks to ongoing developments pioneered by the chemical engineering community.

Historically, chlorine-based oxidation has been the most widely used, and it is very effective. However, the transportation, storage, and use of chlorine (which is highly toxic) present significant potential health and safety risks during water-treatment operations. To address these concerns chemical engineers and others have developed a variety of alternative oxidation treatments that are inherently safer, and in many cases more effective, than chlorination. These include Ultraviolet light,Hydrogen peroxide, and Ozone, each of these powerful oxidizing agents destroys unwanted organic contaminants and disinfects the treated water without the risks associated with chlorine use.

Considerations for constructing a water reclamation system:

In planning for urban reuse there are three major issues that must be considered prior to developing such a system.
The first issue is that year round wastewater treatment and disposal are required when designing any wastewater treatment facility. A water balance for the reclaimed water service area is needed to determine how much wastewater will be generated and how much irrigation demand there is for the reclaimed water. The wastewater generated may exceed the reclaimed water demand during portions of any given year. Therefore, a discharge permit, additional storage, or a designated land application site may be required.

The second issue which must be considered is the constituents (e.g. salts) that may be present in the reclaimed water and what effect(s) they may have on the cover crops that will be irrigated. For specialized users such as golf courses, nurseries, etc., a detailed evaluation of the effluent constituents may be necessary in order to determine whether or not they are candidates for urban reuse irrigation.

Third, Urban Water Reuse is not suitable for all wastewater treatment applications. The manpower requirements and permit reporting can make a reuse facility expensive for a small operation. The facility’s operator in responsible charge shall be a Class I Biological Wastewater Operator. Operation of reclaimed water systems requires on-site operation by a Class II Biological Wastewater Operator or higher operator 8 hours per day, 7 days per week. If the operator can monitor from a remote location and receive immediate notification for alarms, a reduced schedule for on-site operation by a Class II Biological Wastewater Operator or higher operator may be considered on a case-by-case basis.

Deciding how best to use wastewater begins with a laboratory analysis of the substances present in the water. Engineers work with each client to specify the laboratory tests that should be performed. Once that information has been obtained, our engineers and the client:

  • Identify the various ways the water can be used in the specific facility
  • Identify the substances to be removed from the water to make it suitable for each use
  • Determine the process needed to re-condition the wastewater for each use
  • Estimate how much water consumption would be saved by recycling and calculate the annual cost of the water
  • Obtain a cost estimate for the required treatment system
  • Compare the cost savings of reduced water consumption to the capital and operating expenses of the treatment system to determine whether the investment in recycling is cost-effective

Why wait? Start building your water reclamation systems design from the best water reclamation design companies now; get help & assistance from the top highly skilled & technical experts.

/ By Panorama Consulting & Engineering Inc. / Audits and Process Improvements • Sustainable Engineering/ 0 Comments

Improved Energy Consumption Via Heat Integration & Pinch Analysis

A respected tool for achieving energy efficiency is process heat integration with pinch analysis. This article presents an overview on pinch analysis and its mode of employment in operation and process design to achieve energy efficiency gains in real-world. The Heat integration comprises of several techniques that assist engineers to properly evaluate entire sites and processes instead of focusing on individual operations.

This includes knowledge-based systems, hierarchical design methods, Pinch analysis, numerical and graphical techniques. Pinch methods dominate in the area of energy efficiency. The terms heat integration (PI) and pinch analysis are frequently used interchangeably.

Pinch analysis which is also known as process integration, energy integration, heat integration or pinch technology is employed in achieving minimal energy consumption by optimizing energy supply methods, process operation conditions and heat recovery systems. It is a methodology for minimizing the consumption of energy through chemical processes by targeting feasible energy targets thermodynamically.

As a systematic technique for analyzing the flow of heat through an industrial process, pinch analysis’ process data is represented as a set of streams or energy flows. Naturally, heat is required to flow from hot to cold objects in the Second Law of Thermodynamics. This is a major concept that represents the overall heat demand and heat release of a process as a function of temperature.

For the identifications of the Pinch and targets for cold and hot utilities, the Problem Table algorithm is the tool to use. It is a fundamental computational tool. The location where the heat recovery is the most constraint is designated by the Pinch which is characterized by ΔTmin (a minimum temperature difference between hot and cold streams).

As a result, the system can be divided into two separate subsystems that are located above and below the Pinch respectively. Hot utility is only required above the Pinch while cold utility is required below the Pinch. So far, the identified hot and cold utility consumption turns out to be Energy Requirements (MER). Once a heat transfer (cross-pinch) is present, no design can achieve MER.

Redundancy many be introduced by the separation of the original problem in the number of heat exchangers. In order to reduce the number of units, the removal of the Pinch constraint may be necessary especially when the capital cost is high. An optimized cost of operation against the reduction in capital costs will be cleared by extra energetic consumption.

As a result, heat recovery problem will become an optimization of both capital and energy costs which is restricted by a minimum approach in temperature when designing the heat exchangers. For effective heat integration, there is need for data extraction and stream selection in Pinch Analysis. Constant CP is the major computational assumption in Pinch Analysis.

/ By Panorama Consulting & Engineering Inc. / Audits and Process Improvements • Sustainable Engineering/ • • • • • • • / 0 Comments

Effluent Minimization Strategies for Waste Minimization and Cost Reduction

Waste minimization is essential for every industry that manufactures products and incurs cost. In India alone, there are a large number of manufacturers producing simple products such as plastic and this is often subject to the question of waste. It is known that the minimization of waste is the maximization of profit. The consumption of earth’s natural resources is seen as one of the major environmental problems we face in the world today and industrial waste and emissions can have drastic effects both financially and environmental. More so, issues such as global warming and ozone depletion are factors that emanate from local manufacturers. In India alone, the amount of emissions caused by manufacturers is alarming and businesses need to come up with new ways for waste minimization.

Waste minimization & Cost reduction strategies

Waste minimization has become one of the business regulations for businesses in India and thousands or manufacturers have been induced to employ waste reduction programs. However, very few people truly understand the cost that wastes can have on their own businesses or just how much it is costing the environment. It is therefore noted that waste reduction is a tool for creating a better world with more competitive industries.

When looking at waste minimization, there are three main proponents that can be drivers of this new world. These are: people, systems and technology.

  • People: Changing a notion or culture can only be implemented if it is first targeted at people. People influence systems and systems influence technology. People should be educated on waste minimization and cost reduction. They should be enlightened on the fact that the littlest raw material saved in production processes can have multiple uses and benefits and should therefore not be wasted. If the whole of India starts to see waste minimization differently, it may just have a greater effect globally.
  • Systems: Also, a systematic approach should be geared towards measurement and controlling problems that occur with eyes set on maintaining efficiency levels. Apart from the obvious benefits of waste minimization, there are also cost implications. Businesses should therefore put new systems in place to ensure that people are producing efficiently.
  • Technology: Lastly, technology could be a major driver of this new world system. Capital investment should be introduced to improve manufacturing productivity and reduce waste creation. Technology has a major deciding role on the world we live in today. Therefore, technology should be motivating waste minimization and helping reduce cost.

A number of companies have also developed strategies to ensure that there are reduced amounts of waste in manufacturing processes. This is because there is a greater enlightenment on the fact that raw materials can be used for several production processes with even by-products having relevance in the production of commodities. Companies are advised to perform studies of the true cost of waste and should create new strategies for the management of this problem.

Waste minimization and cost reduction should be at the forefront of thoughts for people and businesses in India. It would provide a greater and more efficient world we live in and also reduce the costs of doing business.